Aerodynamics of Gravel Bikes

https://www.renehersecycles.com/aerodynamics-of-gravel-bikes/

by vinceroni • 4 years ago

151 206 4 years ago

cdot2• 4 years ago

"Some readers have suggested that the boxy shape of the bag could be improved. However, since the bag sits between the handlebars, a rounded shape was actually less aero when we tested it in the wind tunnel."

I would not have guessed that. Could a more efficient shape be made?

matsemann8• 4 years ago

Yeah, the round shape is actually not very good. But it's the traditional one, from bicycle frames being welded steel tubes. The circle is still as wide as a square would be, and additionally it creates lots of turbulence. An aero frame is much more tear-shaped.

usrusr• 4 years ago

The boxy shape would likely still be less aero in isolation, but certain parts that in its slipstream might be so un-aerodynamic that the see less drag through more turbulent air than through clean air, and the boxy one provides more turbulence. Or it's the reverse, total drag benefits from the boxy rear and the rounded one was round on the rear as well (or not round at all, just some knotty wrap that approximates "round" very roughly, contrasting with a clean box)

brandmeyer3• 4 years ago

The round-bottom shape that sits under clip-on aero bars is very good.

https://cyclite.cc/en/products/handle-bar-aero-bag-01

https://torstenfrank.wordpress.com/2021/12/07/aerodynamik-vo...

digdugdirk• 4 years ago

This is a great overview of the current state of aerodynamics in cycling. I especially loved the comparisons to what's legal in road cycling and to what the current state of the art is in MotoGP.

Also, MotoGP is absolutely worth a deeper look for anyone who found this article interesting. They've recently started taking aerodynamics to another level with front and rear winglets in a way that wasn't done before.

WA• 4 years ago

Related, this fascinating video, which covers different bag positions, clothings etc.: https://www.youtube.com/watch?v=Ue_Tz7e0DmE

Lio3• 4 years ago

I'd also suggest this Francis Cade video1[1] where they tested various bike packing bags in a wind tunnel.

Bar bags of any size or shape are really slow.

A much better solution is something like a Tailfin aeropack[2].

1. https://www.youtube.com/watch?v=WcXh_oqs_Bs

2. https://www.tailfin.cc/

matsemann8• 4 years ago

A gravel bike is the perfect commuter bike! At least if you're not going electric.

Almost as light and fast as a road bike. But a bit more upright riding so it's more comfortable. Wider and more treaded tires means tram lines, pot holes, curbs etc. are less of a problem and can handle rough surfaces and not just asphalt. Mounting points and wider forks allow for mudguards / fenders so rain is no problem. The wider space allows for studded tires during winter. Also easier to mount panniers / luggage carriers to carry stuff home from the stores.

While I love my road bike for long rides on the weekend, I use my gravel bike daily. And it also allows me to go places I cannot go with the road bike, without having to go all mountain-bikey.

Btw, for road biking we often compare aerodynamics using "wattage per dollar". It can be surprising what then should be the first things to improve.

Steltek• 4 years ago

Gravel bikes are good commuters, if you like drop bars. Many commuters prefer flat bars for the more upright riding position, which allows for a better field of view for misbehaving drivers.

You still also have the classic problem that higher end bikes lose all the commuter friendly features. Carbon forks and frames often lose mounting points for fenders+rack. The marketing vision of a gravel bike is someone expecting to get muddy and who isn't trying to stuff a laptop into a saddle bag. Durable, maintenance friendly choices like threaded BBs and easy cable routing go away. You're stuck with heavy bikes with poor gear ranges, super low end components, cable brakes, etc.

bluecalm• 4 years ago

I agree but there are exceptions. My carbon bike (from GT) has bikepacking mounts on both the frame and the fork. Mounting fenders wasn't a problem either. It also has outside cable routing but not a threaded BB.

I think Canyon is selling bikepacking gravel bike as well (Grizl). There are choices, you just need to look for them. It's true that these days availability is a problem but it's a problem with everything cycling related.

prmoustache17• 4 years ago

Drop bars can be set as high as you want. There are even off road drop bar bikes built with stems looking like goose necks to put the bar high enough (see example in the link). It is more about the position in which you want to put your hands/wrist that matters.

Gravel bikes are sold in many different kinds, and different materials. Steel, alu, titanium, carbon, you name it. They are also build with different use in mind. Some are "racing" gravel with many lightweight high end components, other are made for bikepacking with provision for fenders, front and rear racks and usually more common standards. Those are commuters friendly.

Link: https://2.bp.blogspot.com/-hVZNsMpWmxk/V9rqVdtLBHI/AAAAAAAAQ...

matsemann8• 4 years ago

You're stuck with heavy bikes with poor gear ranges, super low end components, cable brakes, etc.

Hmm, not my experience at all. At least the market here there are no "cheap" gravels. For around $1k-$1.5k (which is the cheapest gravels available here) I've gotten hydraulic breaks, Shimano GRX groupset, an OK weight etc.

CobaltFire5• 4 years ago

My steel gravel bike was built with bikepacking in mind, so it's carbon fork was revised after the first year to have those mounts for exactly that reason (Niner RLT Steel).

antihero2• 4 years ago

Modern drop bar shifters have an upright position though?

Melatonic18• 4 years ago

Extra wide dirt drops with the flare are best in my opinion for everything. They are not like the oldschool flared bars where they flare up and then out - they are totally flat at the center (and wide at the center) and then the drops flare outwards (the drops are not purely vertical). You combine this with an extra long stem (for more upright riding) and you get the best of all worlds. You can ride them like flat top bars with multiple hand positions in the center and there is tons of room for mounting lights or a beverage holder. You can install nice big fat shifters with comfy rubber hoods so you can hold via the hood itself or place your hand around the top of the drop and still brake. And then of course you can place your hands deep in the drops or at the very bottom of the drops.

Fradow2• 4 years ago

I'm in agreement with almost everything except the tires. Unless your commute has a significant portion of rough surfaces, you definitely want to use some road tires. Not the super skinny ones used on road bikes, so you don't have an issue with tram lines/pot holes/curbs, but good reinforced road tires (so you don't have flats when going over glass/nails/whatever).

I've been commuting daily on a mountain-bike (chosen for the comfort of a full suspension and the braking power of disk brakes), and switching from the factory all-terrain tires to road tires about 2/3 the width has been a huge improvement: a lot less rolling resistance, and a lot more grip, especially when it's raining (despite less width).

ehnto5• 4 years ago

I've commuted on a roady, a steel big tire bikepacking bike (basically a hardtail MTB) and now a gravel bike. I'd say the tires on gravel bikes tend to be the best compromise between comfort you get from a big volume tire, and the speed of a road or commute tire. They can run pretty high pressures, which is the biggest factor for rolling resistance, and they're pretty skinny relative to MTB tires.

For me, the minute rolling resistance tradeoff between the gravel tire and a commute tire is worth it. The road and bike network here kinda suck for smoothness, I'd rattle apart if I ran a road tire.

prmoustache17• 4 years ago

There are slick gravel tires. The author of the article sell some of his own brand Rene Herse. They are made by japanese brand Panaracer who also produce slick and treaded gravel tires under its own name and for other companies.

Slick large volume gravel tires are also sold by most bicycle tire brands. Most of them are tubeless compatible which remove the need for reinforced heavy tires as any puncture usually seal itself thanks to sealant.

I've also commuted for years on thin cotton road tubulars so it really depends on the kind of roads your are riding on. But having high volume will certainly improve comfort and also allow for better grip in the wet and better ride when the bike is loaded which is often the case if you are commuting.

Melatonic18• 4 years ago

Quality "touring" tires are amazing for this. They have a little bit of tread in case you need to do some dirt but very minimal. They are extra thick rubber because nobody wants to replace a tire if they are trying to bike 3000 miles over multiple months and they have low rolling resistance. They fit most bikes and come in very useful sizes like 35 or 38C. Schwabe Marathon is the classic choice but there are tons out there!

ehnto5• 4 years ago

I agree, except on the electric part. Where I live e-bikes don't assist over 25/kmph, and I'm always above that... until, my ride home. Which is steep hill, and I'm tired, and I just want to go home. As an all-rounder it's been the best bike I've had yet, I can do just about anything with it. Very utilitarian.

I ride a heap, I ride MTB, commute and also a gravel bike for fun, so I feel no shame getting that e-assist on the commute. I don't need it for the fitness, I'm just getting to work!

One of the big benefits of a gravel bike is indeed the tires, they can be tubeless so no more annoying pinch flats, and they can be run at really comfy pressures depending on your personal preference.

glenngillen• 4 years ago

Depending on the bike/motor you've got, something like this can be very inconspicuously added to your bike to get past the 25/kmph limit: https://planet3.bike

I've one on a Specialized Levo and it works great.

matsemann8• 4 years ago

Sounds like you also live in Oslo? At least the nice thing is that I don't get that sweaty on the way to work..

Not sure if you misunderstood my comment? I'm all for electric bikes (my GF is getting one today actually) and how they enable many more people to bike. I love seeing parents bike their kids to school on this big ebikes, zooming past hundred cars in a gridlock. But _if_ you're not going electric, a gravel is a great bike. If you're going electric, most of the problems a gravel solve aren't really a problem.

criddell• 4 years ago

I bought a steel frame touring bike for commuting and I think it's pretty much perfect mostly because the steel is springy, giving a pretty comfy ride.

Cutting the bike weight or tuning for aerodynamics seems kind of pointless because I have one or two panniers on board to carry the stuff I need for work (towel and dopp kit, change of clothes, lunch, laptop, etc...). Also, exercise is one of the reasons I'm choosing to commute by bike so having to work a tiny bit harder isn't necessarily bad.

Melatonic18• 4 years ago

"Touring" bike is basically just a gravel bike from the 1980s. There are also 1980s "sport touring" bikes that are similar (less specifically designed for long term touring with tons of rack mounts). Some of these are more just like affordable general use road bikes but the better "sport touring" bikes are the most underrated bicycles out there IMHO.

pjc50• 4 years ago

The Dutch style bike is almost perfect for commuting, but for badly maintained roads I would occasionally want one with MTB suspension and tyres.

orthoxerox• 4 years ago

Yes, I've always wanted a "rural bike" to match Dutch urban bikes: upright posture with a comfy seat, fenders, baskets, a kickstand, IGH/belt, but wide tires and maybe even suspension.

Marin Muirwoods RC came close, but was overpriced for a banger bike.

prmoustache17• 4 years ago

Dutch style bikes are perfect for casual city riding, sight seeing and well, riding slowly. Usually when you are commuting and you have more than a couple kilometers to ride you want to do it faster. Dutch omafiets are really bad in term of aero.

wink3• 4 years ago

I think it's pointless to lump everything together as "commute" - sure, if you're lucky and need to go only like 4km without hills then basically every bike will do - but no, I don't want to do 12-15km one way with that, just because I can probably save 1/3 of the time (also gravel vs road)

akgerber• 4 years ago

A Dutch-style bike is perfect for Dutch-style commuting: riding maybe three miles max to the shops or public transit on a high-quality network of bike infrastructure where you won't be bullied by drivers for riding at 8-12mph.

Atrocious US land use & infrastructure makes this less practical for many trips in the US, where destinations are widely spaced to allow for free/easy car parking and evasive maneuvers are often required for safety, and steep/off-road shortcuts are often useful to avoid traveling miles out of one's way on a network of arterial roads designed for fast & easy car travel at the expense of everything else, including human life. A gravel or hybrid bike is better suited for this sort of riding.

MezzoDelCammin6• 4 years ago

umm, hate to break it out to You, but... there's no such thing as a "perfect bike". This is why we have Rule #12 amongst the Velominati, the Keepers of the Cog. "The ideal number of bikes is always n+1, where n is the current number of bikes"

Everyone's commute is slightly different and while I use my gravel as a commuter just like You do, there's always the matter of personal preference.

What if You prefer to ride in regular clothes and "style" is a thing? Those dutch bikes someone mentioned a few comments ago are great for that.

What if You're riding through dense traffic / cityscape half of the time? A narrow bar fixie perhaps?

I like being able to get some exercise while commuting as well, but that's not necessarily true for everyone.

matsemann8• 4 years ago

Of course! But I just wanted to give gravel some love! And spread some awareness of their existence.

I think most casual bike riders don't recognize them as a separate bike from road bikes. So they think it's either a dutch styled bike or a road bike, and if neither fit they end up commuting by car or so instead.

CobaltFire5• 4 years ago

I agree. I ride a Niner RLT Steel with drop bars, 1x10 gearset, 650b wheels, and Panaracer Pacenti tires.

I specify those things because my Bike of Theseus went through MANY variations before I got it to where I was happy!

ActorNightly6• 4 years ago

From a money perspective, there is no reason to buy an analog bike for commuting anymore given the current selection of ebikes, and even more so, aftermarket ebike kits like Bafang. You can buy a single speed beach cruiser for $200, add $1000 BBSHD kit that comes with a battery, and basically get everywhere faster than a top of the line aero road bike.

antihero2• 4 years ago

Well other than that with $1,200 commuter/cx bike you are getting much better quality kit, and are still getting a load of exercise.

nedludd• 4 years ago

These in-depth scientific studies always seem to neglect the weight and aerodynamics of the RIDER. That is surely the biggest factor when it comes to speed and efficiency.

wffurr• 4 years ago

Harder to spend money to improve the rider. Fancy clothing, I guess.

someweirdperson• 4 years ago

Weight reduction is much cheaper on the rider than the bike in many cases though.

Lio3• 4 years ago

A skinsuit or roadsuit will definitely make you faster on the bike. It's pretty easy to measure the effect with a power meter.

Weirdly "aero socks" are both a thing and make a big difference to the point that they are heavily regulated by the UCI.

Any cylindrical part of the bike or rider is going to perform badly so if you can encourage the airflow to stay attached around it you reduce the amount of effort required to move you forward, hence aero clothing being a big deal.

If you're a serious cyclist then it's pretty easy to spend money on good quality clothing.

jrf6• 4 years ago

The rider is a much bigger factor, of course. But that’s not the problem being addressed here. You’re not suggesting the bike should not be optimized are you?

nradov2• 4 years ago

It makes no sense to optimize the bike in isolation. There is complex airflow interaction between the bike and rider. There are changes that aerodynamicists could do to reduce bike drag that would actually increase drag on the complete bike plus rider system.

The problem is that there are so many variables with riders. For example, just a slight change in head position can increase drag more than any improvement in frame tube shape could save.

matsemann8• 4 years ago

It's always funny with people having paid $10k extra to save a kilogram on their bike, and then show up on the Sunday group ride with a beer belly. But I think these articles and study are mostly written for / paid by professionals, and they don't have that much more weight to lose.

But reading "The secret race" by Hamilton (one of Armstrong's team mates), they do focus obsessively on it. They would often ride for hours, then take sleeping medication and go to bed without eating.

giraffe_lady• 4 years ago

They are climbing mountains though. In a flat area this advantage nearly disappears. I have that typical cyclist underweight build and it barely helps me on gravel rides, really only when there's a direct headwind. And it's balanced by how much more I get pushed around by crosswinds.

It's definitely very significant for european-style touring races, but people overstate it for even high-level amateur rides especially in flatter areas. Which is most gravel riding.

brandmeyer3• 4 years ago

It's always funny with people having paid $10k extra to save a kilogram on their bike, and then show up on the Sunday group ride with a beer belly.

Ah, the smell of fresh gatekeeping in the morning. You don't know what road these people are on, just their current state. For all you know, they've already dropped dozens of pounds and are happy with their own improvements. Never look down on a fat person on a bike.

jamincan• 4 years ago

When framed that way, it seems odd, but is it so strange that someone with means spends $10k on their hobby? That's really what it comes down to, more so than the weight-savings. If you like riding bikes, and have the money to spend on it, why not spend $10k on a fancy bike?

brazzy• 4 years ago

This article addresses the rider in detail.

prmoustache17• 4 years ago

You should read the article, rider positionning and clothing is mentionned.

hi• 4 years ago

the fastest riders in the 200-mile Unbound average 20 mph (32 km/h) across the Flint Hills of Kansas.

Let’s not forget that the most important aspect of averaging 20mph on grave roads: drafting, low body weight and high fitness.

If you watch footage of the unbound gravel race they mention, the winners are with a group of riders until the very end.

The fastest riders are professionals sponsored by the companies trying to sell you this aero gear.

If you want to ride faster ride in a group, find your ideal body weight and spend money on a coach. Only then spend money on bike parts beyond the basic lubricated chain, correct tire psi, etc.

MezzoDelCammin6• 4 years ago

Personally, I'd change the order. Coach first, body weight second.

If there's one piece of equipment to buy first & ASAP, it'd be a powermeter and something to display the readout on.

Riding in a group is of course great, but first You got to have the legs to catch up and then the body weight / metabolism to keep up. Having the core / flexibility to be able to spend hours in somewhat aero position doesn't hurt either.

It always makes me laugh to see slightly overweight people on carbon frames. Having a few kilos over myself, I always thought I'd rather spend money / time / effort losing 3-4kg of fat, rather than mulling over how to shave 100g off of the groupset or 300g of wheels weight...

noir_lord• 4 years ago

but first You got to have the legs to catch up and then the body weight / metabolism to keep up.

Not just keep up, if you are riding in a group you need to be fit enough to take your turn on the front where you aren't draughting (at least if the group you are riding with is your team).

The actual team dynamics of professional road racing are fascinating, much like F1 they'll often pick the strongest and expect everyone else to support them.

rich_sasha2• 4 years ago

Yeah but carbon gives you cred, and basically _buys_ you speed. Losing weight is effort.

Sarcasm over, one of the funniest cycling stories i ever encountered. My work had a little low-key "bike club", a few guys cycling on warm evenings. One of the partners was a key member so over time non-bike guys started wiggling in for networking purposes.

One guy, with no clue how to ride, drops 2k++ on a full carbon bike, high end components etc. Cometh the first hill, and we find ourselves waiting at the top. 2 mins, 5 mins, finally 10-15 mins in one guy turns around to check up.

The carbon bike cyclist figured how to shift up, but didn't know how to shift down, and was trying desperately to climb in a downhill gear.

wl2• 4 years ago

There's a difference between weight weenie carbon and using carbon to improve ride feel and aerodynamics. I've got an old bike made out of Reynolds 853 steel that's lighter than my recent vintage full carbon bike.

jackmott426• 4 years ago

Carbon frames don't really cost especially more money than a nice aluminum bike any more.

hengheng• 4 years ago

That's it. Same as in road cycling, the biggest air resistance is not due to the bike frame but due to the rider that will have to sit on it. The larger cross section is hard to ignore.

To improve speed, make the bike more comfortable so muscles can be more relaxed. To improve speed further, reduce cross section while maintaining a comfortable ride. For the last few percent, get a suit that sits tight.

All the rest is for those that want to save five seconds over an ironman ride, where group riding is not allowed. But hey, tri bikes do look cool, have fun.

wyre• 4 years ago

This post feels very dismissive of pro cycling, aerodynamics engineering, and what TFA is about. Any pro cyclist is going to use drafting, a low body weight, and have high fitness regardless if they are racing on gravel or not. An upgrade of only 3% for a pro cyclist could be the difference in making podium or not.

Long distance gravel cycling is a relatively new sport and technology and engineering is still in its infancy. There is only minimal design crossover between a fully aero triathlon bike designed for going 112 miles as fast as possible, and a bike ridden for 350 miles by a top finisher at a race like Umbound XL.

Jan Heine isn’t even trying to sell you aero parts. Maybe tires, a journal subscription, or some nice looking parts, but his brand doesn’t sell aero parts. His website doesn’t even offer the aero fairings he used, nor HS r contact info for the framebuilder that built the bike he raced.

prmoustache17• 4 years ago

In fact there are already some changes in the way gravel is raced and there have been some waves in recent races. When reaching an optionnal resupply/refill point it used to be the case that if the leading 4-5 riders were calling for a pitstop the whole group would stop and wait for anyone to take food and drinks. Now some riders will decide they carry enough and not wait for those that decided on carrying less and stop more often and some additionnal strategy is being put in place. Also some elite riders are calling for a ban of aero handlebars, at least for the fastest ones who fight for the win, in the ground of safety reason. Many stopped using aero bars to set an example but others despite agreeing on the safety issue will continue to use them until a rule is set in place to ban them because they don't want to give up any possible advantage.

ben77994• 4 years ago

He is most definitely trying to sell you parts. Just not aero parts, and this whole article is partially marketing to tell you a bunch of the aero parts don't really matter, so you should buy his parts instead, and use his tires, etc, etc..

And he of course conveniently ignores all this stuff makes about 1/10th the difference rider fitness makes. He is a very fit/accomplished racer, at least he controls that variable, he does most of the test riding himself.

jamesbfb• 4 years ago

Unless we’re talking about climbing, weight isn’t _everything_. I would argue that being able to stay in an aero position (go on YouTube, but essentially, get on the drops, elbows in, etc) for longer periods is far more important, these aero gains similarly applies to deep dish rims.

All that said, I do agree with your sentiment that shedding a few bricks is going to be more beneficial than shedding a few thousand on a new bike (or rims!). Hell, you might save yourself a divorce in the process!

jackmott426• 4 years ago

Lubricated chains and aerodynamics save you energy in a group too.

benjaminwootton• 4 years ago

I bought a cool book yesterday which is all about gravel trails in the UK. I had never heard the term gravel bike until reading it.

Silly question but can I do these trails on my full suspension mountain bike, or will I be mercilessly mocked and possibly chased out of town?

I already have a mountain bike and a road bike so not keen to add a third!

protonbob• 4 years ago

You will certainly not be. At least in the US, mountain bikes for trails are still the norm.

namdnay• 4 years ago

A mountain bike is fine on a gravel trail, if you can lock the shocks

unklefolk• 4 years ago

... can I do these trails on my full suspension mountain bike...?

Yes. It will be a bit more work on the pedalling front vs a dedicated gravel bike, but I doubt you will encounter any bike snobbery. I have gravel trails near where I live, and you see all kinds of bikes tackling them.

lukah• 4 years ago

If anything, you might be thankful of a full suspension mountain bike on some of our "gravel" trails in the UK. There's such a wide range from US-style back county roads all the way to bridleways with baby-head sized rocks that you probably wouldn't want to be riding on something typically sold as a gravel bike.

Doctor_Fegg• 4 years ago

Yes, this. There's actually not that much US-style "gravel" in England and Wales: basically a few Forestry Commission tracks in mid-Wales, Northumberland and places like that. Elsewhere it's single-track bridleways that dominate. Routes like King Alfred's Way, the Pennine Bridleway, the Great North Trail and West Kernow Way are sometimes marketed as gravel routes but they're probably more MTB than anything.

MezzoDelCammin6• 4 years ago

"gravel" is more of a mindset. Yeah, granted, it's been taken over by most marketing departments trying to push people into buying new gear, but ultimately, it's about being able to ride both paved roads and whatever tracks are there in the outdoors nearby.

There's always the debate / meme of "are gravel bikes just 1990's hardtail mountain bikes with drop bars?" and ... the jury's still out on that one ;-)

AFAIK a full suspension is an overkill, but if it's what You got, go for it. You'll just be a bit slower.

If You're looking for some testing, perhaps try to just get yourself a new pair of gravel tyres that fit Your wheels. That's by far the biggest source of resistance. If it's fun, pick up from there. There are plenty of videos on youtube on how to hack into a gravel bike a cheap old frame (either hardtail MTB, or some CX / touring frames). Doesn't have to more than 100-200EUR / USD in the end.

wink3• 4 years ago

It will certainly be more of an effort with the fully, but I don't see anything wrong there. I'm not even sure we have a lot of so-called gravel trails here (not the UK) but the norm is more: people ride on MTBs and sometimes there's a rider on a gravel bike or cyclocross.

I already have a mountain bike and a road bike so not keen to add a third!

Why would you say that? :)

intrasight• 4 years ago

Any bike you ride on gravel is a gravel bike. All my bikes have been on gravel so they are all gravel bikes.

dev_tty01• 4 years ago

Yes! First, if you haven't spent much time on gravel, you will be more confident and sure-footed on the MTB. Second, you will have a much more comfortable ride. As others have said, it will be a bit more effort, but the improved confidence will probably do more for your overall speed than a skinny tire.

I would however lock out the rear suspension, and probably the front too. The high volume tires at the right pressure will likely provide all the suspension you need for gravel and your pedaling will be more efficient.

As far as being mercilessly mocked, that reminds me of an old adage. We spend our youth worrying about what other people think. In middle age we decide we don't care what other people think. As we get older, we finally realize no one was thinking about us.

ehnto5• 4 years ago

If you want an astonishgly well put together deep dive on gravel and bikepacking aerodynamics, check out: https://www.cyclingabout.com/fascinating-aerodynamics-bikepa...

I cannot recommend him, his videos or articles enough. He lives on the bike, literally, and he applies an unrivaled dedication and passion to thinking and writing about this stuff while on the road. He has tests, science and real world experience to back him up too.

pharmakom2• 4 years ago

I’m sorry but Jan Heine has unscientific methods and his products are of questionable reliability. You can drop 200usd on his tyres. It’s like hifi nerdy but for rubber.

bigfudge2• 4 years ago

I agree the tyres are expensive, but their findings on tyre width and pressure are largely bourne out by more controlled tests.

In addition, their rolling distance tests include one factor which most standardised rigs didn’t: the losses from hysteresis when uneven surfaces have to lift/return your mass over a bump. I think soft wide tyres would be even more advantageous than most people realise once real losses on real roads are factored in, and compared at speeds most cyclists go at (i.e most people don’t average 30kph). In fact, even using average trip speeds as the comparator would be daft because that would include downhill sections where riders are actually braking, or don’t really care about rolling resistance because the difference between 50 and 55kph downhill makes no practical difference.

ActorNightly6• 4 years ago

The tire width definitely has a break even point where wider tires are significantly less efficient than narrower ones unless you run them at unsafe pressures. More volume in the tire means that at the same pressure, there is more deflection, and deflection hysteresis in the tread, notably the rebounding of the tread behind the contact patch is what causes the rolling resistance in the first place.

7622362• 4 years ago

Where are the supposed alternative people with scientific methods?

pharmakom2• 4 years ago

I don't know but I'm also not trying to market very expensive tyres.

wmorein• 4 years ago

Two of the best people who are not selling anything are Tom Anhalt (http://bikeblather.blogspot.com/) and Robert Chung. They both post a lot in various forums like Weight Weenies (which is more about rolling resistance and aerodynamics now that we know that they are more important) and Slowtwitch (more triathlon focused but has a lot about general bike tech).

Josh Poertner from Silca is also good but has things to sell.

Of course what everyone is saying above is right -- fitness and rider weight matters the most. But it is fun to look at this stuff especially once you have achieved some level of fitness.

Dave_Rosenthal• 4 years ago

bicyclerollingresistance.com

alleycat5000• 4 years ago

Bicycle Quarterly (magazine by the same folks) is a great read, always such a joy when it arrives in the mail!

https://www.bikequarterly.com/

bbarn2• 4 years ago

I am an out of shape former racer who has ridden his bike 10 times in the last two years. I have a dad belly and rarely work out at all. I recently did The Rift this summer - a 200km gravel race here in Iceland that people come from all over the world to race. I did it on a carbon cyclocross bike from my racing days with file treads. I felt like the light weight of my bike outweighed just about every gravel fad that's out there right now. I was flying past people on the hills, and while the ride felt very rough on the high speed flats, I was still going fast. If I were in my racing shape of a few years ago I think I would have been in the top 5-10% of racers, largely because nearly everyone was on giant heavy gravel bikes with massive tires loaded for friggin bikepacking from the look of it. My wife has a purpose-built gravel bike, and she commented on just how slow it felt going uphill (she is a former state cyclocross champion).

With the exception of the absolute professionals, most people "Racing" these events are just there to finish them, and the pros? It's basically just a road race. Gravel offers no significant challenge in handling your bike, and any reasonable set-up can win if it's light enough and the rider is fit enough. The Aero arms race certainly matters in time trials, but I remain unconvinced there's enough benefit for the actual racing. I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too.

shagie• 4 years ago

I know US Midwest gravel races are effectively flat, but acceleration is greatly improved with a light bike too.

While this is a "on the paved road" race... you should check out Horribly Hilly Hundreds in Wisconsin - https://www.horriblyhilly.com

gammarator• 4 years ago

Yeah, rolling hills are tough…. “Rouleur” is a cyclist type for a reason.

jackmott426• 4 years ago

Why don't you actually do some math, or experiments, rather than just telling us you have doubts?

This is all really easy stuff to answer. For instance. 75kg rider + bike. Make the bike 1kg lighter. Go up a 8% grade for 1 kilometers at 300 watts Time saved by 1kg weight reduction? 30 seconds out of 40 minutes.

Or suppose we add 300grams to the frame to make it aero, which is typical. If that reduces the CdA by .02 out of .25, you are at about a breakeven point. JUST during the 1km climb. Then you save time on all the flats and non technical downhills.

Acceleration is even less affected by bike mass. People forget that bike mass is a tiny % of total system mass (our fat asses). And mass is only one of 4 major components that affect acceleration. I'm happy to run through some acceleration scenarios if you like.

gergely3• 4 years ago

You are correct on the watt, weight computes but I think the aerodynamic saving is worthless on a gravel race. People are not going that fast on gravel to gain anything from aerodynamical optimisations. You need to keep going at least 40 km/h to have any advancement without up-down movement which is obviously not something that you can achieve on gravel.

cycomanic• 4 years ago

The issue is that a lot of the aerodynamic frame advances only work in ideal laminar conditions. However wind is gusty, there are trees and other obstacles next to the course etc. In those cases the advantages largely disappear as Hambini has shown.

metadat2• 4 years ago

I'm happy to run through some acceleration scenarios if you like.

Yes, please continue! I'm digging your analysis.

vikingerik2• 4 years ago

I know nothing about typical bike timings, but I was struck by that. Does it really take 40 minutes to go 1 km at an 8% grade? Would it be faster to get off the bike and walk? When you're not rolling, you don't have to output power to fight your own weight trying to roll back - the friction between your shoes and the ground counteracts that. (I assume a real race doesn't allow you to walk, just batting around thoughts hypothetically here.)

bbarn2• 4 years ago

You're forgetting the effect of exertion on the rider under heavy loads like climbing.

I've ridden heavy bikes, and I've ridden light bikes. Light bikes feel better, rotational weight mattering more than anything else.

ben77994• 4 years ago

I'm a former racer too and this constant equipment arms race and arguing is just so fatiguing.

People can argue about analytics around equipment till pigs fly. It's all still just an order of magnitude smaller than the differences between being fit and not fit and a stronger rider versus a weaker rider or a coached rider versus un-coached rider.

The sport has separated into riding enthusiasts and equipment enthusiasts and the bike companies have completely brainwashed equipment enthusiasts.

Your times don't make any sense either... 8% for 1km takes vastly less time than you're talking about at the power levels you're talking about. You're probably off an order of magnitude there. A rider with an FTP of around 300 will probably climb closer to 10km @ 8% in 40 minutes.

Nothing is more tiring than being at the start of a race and there's someone with a $10k+ bike and a gut talking smack about bikes to someone everyone else knows is going to win the race and the guy with the $10k bike is getting dropped & pulled from the race. One person spent all their time on training and the other spent all their time researching & buying equipment.

ActorNightly6• 4 years ago

You are assuming that rider can output X watts continuously. This is not how humans work. Riders have different profiles in terms of torque vs rpm from their legs. A lighter bike means that a rider is outputing less torque, which he/she can sustain without downshifting to a lower gear, leading to overall increase in time not only during the climb, but also how much energy the rider has left in the tank after the climb for the rest of the course.

prmoustache17• 4 years ago

There is actually very little difference between a cyclocross bike and a lightweight gravel bike. Slightly lower BB, slightly longer wheelbase, sometimes slightly different headtube angle, flared handlebars. Actually the first gravel bikes were rebadged cx bikes. You can race cx with a gravel bike and race gravel with a cx bike. The rider makes most of the difference.

jackmott426• 4 years ago

And you can do fine in a road race with a gravel or cyclocross bike! Just gotta put appropriate tires on.

dc-programmer2• 4 years ago

Cyclocross bikes also have higher bottom brackets

brandmeyer3• 4 years ago

You can race cx with a gravel bike and race gravel with a cx bike.

Sortof. The key defining difference is that a cyclocross bike meets the UCI rules for cyclocross, while a gravel bike doesn't. In a sense, the gravel bike trend is the result of consumers rejecting the UCI's definition of what an off-road-capable drop-bar bike should be.

metadat2• 4 years ago

So much bicycle acronyms and initialisms makes for a challenging read for the uninitiated (like myself)! I've researched the terminology and happily share in hopes you too will find it useful:

1. "lower BB" references a lower bottom-bracket, the part that holds the axle to which the cranks attach.

2. "CX", or cyclo-X is short for cyclocross, which is a style of bicycle race which takes place over varied terrain conditions such as pavement, wooded trails, grass, steep hills and obstacles requiring the rider to quickly dismount, carry the bike while navigating the obstruction and remount.

https://en.wikipedia.org/wiki/Cyclo-cross

https://en.wikipedia.org/wiki/Cyclo-cross_bicycle

The cyclocross bikes appear similar to road racing cycles, the major differences between them being frame geometry, and wider clearances for cx bikes to fit larger tires and generally still function after accumulating large amounts of mud and other debris.

edit: Thank you @jerrycrunch! I've incorporated your bb info.

Melatonic18• 4 years ago

Geometry is actually probably the big difference - cyclocross bikes are designed for small repeatable courses often with tight turns and the need to carry the bike on your shoulder. A slightly lower or higher BB height would probably work well for either - it is the ratio of total height vs top tube (so height vs length of the frame) that really defines cross vs gravel. Cross bikes will be taller and shorter (length wise) to have shorter turning radiuses and slightly lower weight at the expense of long term rider comfort and stability at speed. Gravel bikes will be longer and have worse turning radiuses but slightly better stability at speed. You can see the same thing with cars. A shorter bike (just like a short wheelbase vehicle) will also have better approach angles relative to its height.

That being said depending on your leg length to upper body torso length you can of course size a cyclocross bike up or a gravel bike down and achieve sort of the same effect. In my opinion these types of geometry questions do not come up nearly enough in relation to the rider, however, as someone with a very long torso is going to be quite uncomfortable with a bike with a short top tube even if the "size" of the bike is correct for their leg length / height. And of course the opposite can also be true. Ideally we should be sizing and matching frame geometry to the persons geometry regardless of the intended use case of the bike.

scott_w4• 4 years ago

I think you’re overestimating the ability of most of your competition. As a former racer, you probably have leftover power and you know how to race. It was less about your bike being “light” and more about your personal ability.

7622362• 4 years ago

Their "giant heavy gravel bikes" were probably a few pounds heavier than your CX bike, but your dad belly made you like 10 or 15 pounds heavier. Heavier people go faster down hills. I'm unconvinced that their bikes slowed them down, unless they were also super un-aerodynamic (wide handlebars, attaching water bottles to the forks, upright positions, flappy wind jackets)

mauvehaus• 4 years ago

To quote someone I met thru-hiking: "Food is lighter once you eat it."

Or in other words, subjectively, weight on your body doesn't cost as much as weight you're hauling whether on your back or on your bike.

Nope, I can't explain it either, but I've got over 3000 miles hiking/backpacking and it holds true. Can't measure it, didn't try, but I can assure you that feeling worn down is roughly equivalent to being worn down. Getting a pound of weight off your back and into your belly (or the reverse when you fill up with water) is noticeable.

sorenjan2• 4 years ago

If most people are there just to finish then comfort should be more important than speed. In that case big tires and more relaxed geometry makes perfect sense.

Melatonic18• 4 years ago

Are gravel bikes heavy now? From what I remember (admittedly 10 years ago) "gravel" bikes were pretty much cyclocross bikes to begin with just with slick tires.

I sold my fancy lightweight cyclocross bike around this time and built myself a fully custom bike with a hodgepodge of parts - I wanted something that looked a bit vintage cool and also not as stealable so I went with the pinnacle of late 1980s touring frames (steel) which is obviously not light but not all that heavy either. Bought lightweight 29er rims + 35C quality touring tires, wide flared dirt drop bars, nice 9sp bar end shifters with a triple crank up front (9sp being my favourite in that you can still friction shift it easily if needed and the bar ends can easily switch from indexed to friction at the flick of a switch). The thing absolutely flys on gravel, pavement, dirt roads, shitty sidewalks - basically is my do everything bike for general use from groceries to exercise.

guywithahat• 4 years ago

I think he's including fat bikes in that ranking, actually competitive gravel bikes are not heavy at all. I know the Allied Able and Echo have won some races and although it comes with slightly heavier tires it's not too far off from a road bike https://alliedcycleworks.com/collections/able https://alliedcycleworks.com/collections/echo

Anything that's made of metal symply was never competitive to begin with

helsinkiandrew• 4 years ago

The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider

There's lots of things you can do - apart from losing a lot of weight, clothing and helmet design is probably the simplest, there's some good references to things that can be done here: https://link.springer.com/article/10.1007/s12283-017-0234-1#...

I don’t always use the aero tuck. I find that it’s not very comfortable for more than a few minutes at a time

I cycle on a time trial bike (not on gravel) - which has a higher saddle and longer frame so back and arms can get straight and horizontal. It took a lot of effort to get comfortable physically and mentally in that position (you hands feel a very long way from the brakes) and you do loose quite a bit of control in that position, but I don't see why a slightly higher saddle and arms horizontal but wider with hands at the edge handlebars in line with legs wouldn't be possible.

prmoustache17• 4 years ago

The most aero time trial like position need training, especially the muscles in the neck area. Even in the pro racing world some racers do not train enough in that position and lose precious time in time trial because they are unable to keep it straight looking at the road constantly and move the head up and down constantly. The helmets manufacturers actually accounted for that and moved to time trial helmets with a much smaller tail as it spent to much pointing in the air.

seadan83• 4 years ago

Gravel has washboards, pot holes, trenches, lips, fallen trees, overhanging trees/brush, large rocks. I'm thinking a lot about downhill riding too with respect to your comment. For a downhill section on gravel, for a 8% grade descent - safety is perhaps the biggest limiting factor. In some gravel races, it is really debatable whether a hardtail or a gravel bike is better. That is all to say is that stability demands can greatly vary from one section to another on a gravel/mountain race course.

qwertox2• 4 years ago

I started biking around three years ago. Lots of biking, like 5000-8000+ km a year.

As long as I don't weigh my ideal weight and aren't planning on becoming a machine myself, I have zero interest in spending anything in optimizations which will make my bike a better one. I don't care if it could go faster or be more lightweight, spending 600€ for the bike was enough. The cheapest 30€ Schwalbe tires are good enough; I didn't even have a single flat tire this summer after I learned to avoid driving over blackberry branches.

And I really enjoy it. During this summer, with the extreme heat, where I loved the 28°C in the shade of the woods I was thinking about how much I'm going to hate this fall, and now that it's here, I love breathing that cold, fresh air and smelling the humid forest. The only thing I hate is when there's frozen snow on pavement in the winter.

The only thing I spend money on for biking is quality clothing appropriate for the seasons and accessories like good smartphone holders or bags.

chitowneats• 4 years ago

I appreciate your approach but the reason people like optimizations is for speed. The thrill of riding fast is what keeps a lot of us coming back.

lm284692• 4 years ago

Lots of people optimise because they fell in the rabbit hole of optimisation and it became an addiction. Like in every hobbies some people completely lose touch with reality. I've seen videos of people comparing weight of bicycle seats and how to shave like 13 grams of weight of the bike, meanwhile the dude had a dad bod and shaving his torso would have shaved more weight than his $$$ seat

qwertox2• 4 years ago

Don't get me wrong, I also love to go down a forest path at 45 kph to the point where I get scared, but I know that I also have to go up again. But going as fast as possible on a horizontal path is not attractive to me at all. If I want to expend energy, I prefer to ride up a hill where I then can have the fun of riding down, even if I have to pedal 20 minutes up to then go down within a minute or two.

But I also recognize that there are those who are already super efficient and want to get the absolutely most out of their gear, even improving it as much as possible, which is really ok by me. I wish I were at that point, but I think I'd first have to go to the gym for that.

prmoustache17• 4 years ago

There is riding fast and there is riding fast but just a tiny bit slower.

I have a modern race bike, less than 3y old with some but not all of the latest aero features. I also still own my 30y old racing bike that I used to race until 20years ago (it was already old bike then). It stays at my parents place and I ride it maybe twice a year. If you ask any bike reviewer he will tell that old bike is obsolete, feel much slower and make me lose 45s over the course of a 50km ride according to the data given by the manufacturer. If you ask me, sure I feel a difference, mostly in feeling, when I start riding the bike. But after 5 minutes all this is forgotten and I enjoy the ride as much as on my more modern bike. And that bike is perfectly fine surrounded by superbikes in a group ride. Actually I did one this summer with a group that tend to stay together but ride at a fast steady pace until the last 20k where the wait "policy" disappear and people start to attack the climbs at max pace. I ended up in the 5 rider leading group out of maybe 40 and I was totally out of shape.

That old bike would sell for 300-400€ in the second hand market right now. The difference with a 2k and 8k modern bike is much lower.

lm284692• 4 years ago

Reminds me of this bicycle subreddit where they spend thousands on bikes and cosplay attires to get smoked by 60+ years old dudes on 40 years old bikes

As a casual rider you'll be the bottleneck for years before your gear matters even the slightest

8ytecoder• 4 years ago

There’s also a saying in bike communities, along the lines of, it doesn’t get easier you’ll only ride faster. Riding a heavy bike with no aerodynamics will lead to building strength faster. While it can be a bit frustrating if you’re new and riding in a group, joining more beginner friendly groups and upgrading the bike later is much better overall.

It is however really important to get the posture and pedaling technique right. Way too many people in expensive gear do push-only instead of a push-pull. That’s like biking 101. It’s much better to get that smooth pedaling and core support. It’ll prevent injuries and fatigue.

elliottkember• 4 years ago

I've been circling the fountain pen reddit for a little while now and it's a similar thing. They spend thousands on pens, import ink from Italy, buy fancy paper, but their handwriting looks like a doctor's scrawl.

cheeze• 4 years ago

The bike subreddits are super painful. Mainly full of "Freds"

IMO there is not actually a ton of what you talk about. If anything, it's the opposite, a ton of really inexperienced folks posting about their first 20 mile ride. Note that this isn't a bad thing, just that serious cyclists aren't really hanging out there.

Calling a kit cosplay attire is silly though. There are huge benefits to a bib and a jersey.

I'm not wearing spandex because I need to be the fastest guy. I'm wearing it because it has a chamois, convenient pockets, and is a bit more aero (which means that days with a killer headwind are slightly less bad)

mariusor• 4 years ago

As a casual rider you'll be the bottleneck for years before your gear matters even the slightest

For absolute performance, maybe, but for enjoyment of riding the gear definitely matters. For a beginner it's important that the ride is enjoyable so they don't get discouraged and call it quits.

For relative performance against yourself, and in all honesty that's most of us really get out of it in the end, it's good to see times drop and speed increase just because you bought a better bike.

For me it was the other way around, I moved from a very aero cheap fixed gear to a boxy (but with a plentiful cassette) midlevel gravel bike. I was expecting that the gears I had extra would make me have faster times, however the fat tires and less aero profile makes me about half a minute slower for a 6km round. The power I'm pushing however, has increased, maybe because I can keep it more uniform by shifting to lower gears when I get into windier sections. Shrug.

All I want to say is that good gear is beneficial, maybe not for performance, but definitely for enjoyment of a ride. And at the beginning that's pretty important for someone to build a habit out of riding.

wink3• 4 years ago

I'm not here to advocate for expensive equipment but my cross country hardtail MTB (even with the wide tires on the roads, non-carbon) feels like half the effort to pedal than my old crummy commuter trekking bike with narrower tires, so I guess your 600€ bike might already have one of the biggest optimizations packed in ;)

scott_w4• 4 years ago

That’s absolutely fine. This article is aimed at people who race bikes for fun and for a living.

Melatonic18• 4 years ago

The thing is that expensive isnt always better - those "cheap" Schwabe tires are actually superior than most specifically because of the way they are designed - not because they are cheap or expensive (touring style tires). You could also buy more expensive touring tires and they would be better than those cheap ones - but expensive tiny skinny tires would not (nor would big expensive nobby tires). As someone who did a lot of different bike riding and has built many bikes there are also many benefits to going pricier other than just being a wannabe racer - but in the end it is more about choosing the right style of component for the job vs just buying what is priciest or trendy.

heywherelogingo• 4 years ago

Lots of biking? My commute alone: ~10 000km. A 600€ was crap twenty years ago. Contributions are great when the person making them has something to back them up.

Zigurd• 4 years ago

They milk the topic. This could have been 2 pages at most: Aero bars are dorky, doubly on gravel, but they will make the most difference. Heck, clip a fairing to those aero bars. But nobody uses them because you look like a dork. If you can't get over looking like a dork, and you are susceptible to bike marketing <cough>GCN</cough> you'll spend thousands on an aero frame. And then you'll put a hipster handlebar bag on it.

simonebrunozzi• 4 years ago

The biggest part of a bike’s wind resistance is caused by the rider. Unfortunately, there isn’t much you can do with respect to the airflow around bike and rider.

I have an idea about that, and I would like to explore it. Not having a mechanical engineering background, what do you think would be the best way to build a prototype, patent it, etc? Is there any engineering firm that would provide such service, let's say in Europe?

SavageBeast• 4 years ago

I ride a Trek Domane 5 AL which allows spacing for a 48mm tire ( odd for a roadie ) - so I put a 48mm gravel tire on it and started riding it on light gravel. Works very very well. Carbon would be even better but Id still be waiting on it to arrive from the factory alas the aluminum version will have to do. The best bike in the world is the one you have in the garage to ride today.

grzes• 4 years ago

wondering if i should switch handlebars to narrower one. so currently i have 56 frame with 42 handlebars - thats "factory" setup. i noticed that also 54 frame has this handlebars, only 52 size frame comes with 40. anyone has any experiences how it will affect bike handling? i noticed that there is a trend rising to go with narrower handlebars on gravel bikes

Melatonic18• 4 years ago

I personally go with the widest handlebars I can. You might gain some aero from skinny ones which would be worth it if you are racing at a high level but you will lose a significant amount of comfort. Wider bars allow more hand positions and are significantly more comfortable for me especially on long rides. Being able to really get a wide grip occasionally feels great on the shoulders. And on top of that you feel much, much more secure with a nice wide grip on difficult terrain like shitty pothole laden roads.

NegativeLatency• 4 years ago

The aerodynamics of upright bikes compared to recumbents remind me very much of stock car racing compared to f1. Where one is actively pushing forward in terms of speed and performance and the other is stuck with one type because of how it "should" conform to previous ideas of what a bike looks like.

Melatonic18• 4 years ago

Back in the day I found some vintage "aero" bars that were designed to bolt on to any bicycle made before larger diameter drop bars became the norm. I did not want them, however, specifically for the "aero tuck" - I wanted them to give me more hand positions for long term comfort. While I eventually got rid of them because they took too much space on the flats of the bars due to the way they clamped I always wondered if we could design something like an aero bar but specifically for comfort. It could bolt on to the stem or in a way that still allowed multiple hand positions on the flats. The elbow pads were also a very nice way to get some lower back stretches in and I even ended up mounting a small cyclocross brake at the end of one of the aero handles so I could comfortable adjust speed (rear brake only - front brake in this position might be suicide) while going downhill and tucked. Or hell - maybe even something that had a small fold mechanism so that you could fold away the forearm / elbow pads when not in use!

phlipski• 4 years ago

The article mentions the upper back fairing of a motoGP racer but then blows off the idea for a cyclist because they might get too hot? I've always wondered why road cyclists don't ditch their frame mounted (and drag inducing) water bottles for a camelback. The original camelback was slim and I can't imagine it added any drag seeing as it sits on the back of the cyclist. Plus it has the advantage of allowing the cyclist to maintain a better cylcing position without having to reach down for a bottle.

But then again if roadies were really all that concerned about aero and efficiency they'd switch to recumbent bikes...

vbarrielle• 4 years ago

In pro cycling it's actually forbidden to have aero fairings on your bike. During the Armstrong years there has been a controversy about the placement of his radio on his back during time trials that would incur fairing.

Aerodynamics of Gravel Bikes

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