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Aerodynamics of Gravel Bikes

renehersecycles.com

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Re: Aerodynamics of Gravel Bikes

#31

Post by ehnto »

Fradow wrote: post #26
matsemann wrote: post #5

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 sp…

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…

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.

Re: Aerodynamics of Gravel Bikes

#32

Post by MezzoDelCammin »

hi wrote: post #13

> 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 tryi…

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...

Re: Aerodynamics of Gravel Bikes

#33

Post by orthoxerox »

pjc50 wrote: post #30
matsemann wrote: post #5

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 sp…

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

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.

Re: Aerodynamics of Gravel Bikes

#34

Post by bigfudge »

pharmakom wrote: post #28

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.

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.

Re: Aerodynamics of Gravel Bikes

#35

Post by hengheng »

hi wrote: post #13

> 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 tryi…

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.

Re: Aerodynamics of Gravel Bikes

#36

Post by Fradow »

ehnto wrote: post #31
Fradow wrote: post #26

Earlier quoted context omitted.

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…

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…

Thanks for the feedback! I've not had the occasion to try gravel tires.

For me, the main reason to use road tires is grip on asphalt, not rolling resistance improvment. On your commute, you may need to stop in an instant, and more grip = quicker stop = safer (I've had a few close calls, especially downhill under rain).

Obviously, that's also dependent on your regular commute road condition.

Re: Aerodynamics of Gravel Bikes

#37

Post by wyre »

hi wrote: post #13

> 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 tryi…

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.

Re: Aerodynamics of Gravel Bikes

#38

Post by prmoustache »

Fradow wrote: post #26
matsemann wrote: post #5

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 sp…

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…

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.

Re: Aerodynamics of Gravel Bikes

#39

Post by noir_lord »

MezzoDelCammin wrote: post #32
hi wrote: post #13

> 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 tryi…

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…

> 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.

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