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Aerodynamics of Gravel Bikes

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Re: Aerodynamics of Gravel Bikes

#191

Post by qqqwerty »

MezzoDelCammin wrote: post #113
wl wrote: post #49

Earlier quoted context omitted.

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.

The "ride feel" argument is something I quite frankly never understood. I guess it's because I don't do competitive road racing (more of an ultra / bikepacking sort of guy). When I was shopping for my current frame (Kona Rove), I picked up the steel version mostly for maintenance / mechanical reasons more than anything else. Don't see much of a difference in "feel" from my old aluminium road to be honest (other than…

It is subtle, but you will know it when you feel it. Aluminium frames can be engineered to have more flex, and some steel frames can be overbuilt to a point where the "steel feel" is diminished. So comparing any two random frames may not be sufficient to capture the feel.

Also the feeling is subtle enough that the components on your bike can be the larger factor. Tires, crank arms, handlebars, tire pressure, etc.. will all play a factor. Swapping all of your components from one bike to the other would be the best test, but unless your components in aggregate provide a "neutral" feel, it is possible that they could overwhelm the feeling that a different frame will provide.

Re: Aerodynamics of Gravel Bikes

#192

Post by prmoustache »

brandmeyer wrote: post #105
prmoustache wrote: post #67

Earlier quoted context omitted.

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.

> 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.

A gravel bike is perfectly allowed by the UCI. You just have to mount CX tires (width 33mm) on it.

Re: Aerodynamics of Gravel Bikes

#193

Post by prmoustache »

Melatonic wrote: post #161
gergely wrote: post #78

Earlier quoted context omitted.

You have just proved you haven't rode a cyclocross bike. Since those bikes' center of mass is higher than the road bikes it is really "nervous" on high speeds for example long descents.

not true - the "nervous" feel is because people also tend to ride cyclocross bikes that are shorter (top tube length). There is no reason a cyclocross bike cannot be designed with the higher bottom bracket AND a longer top tube - I never understood why the frames were designed like this in the first place (maybe for weight savings?) edit: Realized it is for turning radius

I always raced CX bikes that had the same top tube length as my road bike but usually with a 1cm shorter stem for a slightly more upright position.

Re: Aerodynamics of Gravel Bikes

#194

Post by bigfudge »

ActorNightly wrote: post #153
bigfudge wrote: post #34

Earlier quoted context omitted.

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 re…

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.

Totally agree. I do think that people underestimate the width of that point tho. For most people who are not racing the suspension benefits probably outweighs the minimal aero loss, but it’s really hard to measure. I have been on fast group rides on 48mm slicks and although I get funny looks (and am not going to win many races because I’m old and lazy) I genuinely L find it easier to keep up than on 28mm tyres i had previously. Part of that is confidence maneuvering at speed on fairly crappy roads though.

Re: Aerodynamics of Gravel Bikes

#195

Post by prmoustache »

dc-programmer wrote: post #151
prmoustache wrote: post #96

Earlier quoted context omitted.

That is what I mentionned by "Slightly lower BB" for the gravel bike, just stated in the opposite direction. It doesn't matter much anyway and CX bikes from US brands had already started lowering the BB of the CX bikes because US courses designers are usually less keen on putting off cambers section than euro courses designers.

Sorry somehow missed that. The explanation I heard for the traditionally higher brackets is that it facilitates quicker turning. Is there truth to this or is this more of a marketing thing?

I think it is a mix of many parameters and the main one was that when cx was invented people were using toe clips with straps, albeit looser than on the road and they would hit the ground until the rider has put his foot inside when the bottom bracket was too low.

The rest is mostly the ability to pedal in the corners without clipping a wheel, which help maintain and feel grip, tradition and also to help on the many off camber sections the courses used to have.

I think quicker turning has never been the true reason imo.

Re: Aerodynamics of Gravel Bikes

#196

Post by stevage »

ben7799 wrote: post #144
jackmott42 wrote: post #128

Earlier quoted context omitted.

You are right I had the gradient off by 10x, sorry that should have been obvious, it has been a while Actual time savings of 1kg of weight reduction: 1 second And personally I've used aeroweenieing to podium in a cat 3 road race, and my wife has set state records and won pro races. You can make fun of fat guys doing a professional job if you like but it isn't just them.

If spending lots of money to win a Cat 3 race and knowing you did it with money and equipment instead of fitness and smarts is OK with you more power to you. But if it means thousands of dollars spent on a race that likely paid This isn't really funny, it's a fundamental problem with cycling as a sport that limits who participates in the sport and hurts the sports ability to find and develop the best riders. It seems…

In almost every hobby there are people who get enjoyment from choosing and buying equipment and others who just want to do the thing. Look at people with massive collections of beard games they never play, people with any cameras and lenses but little output, etc. It's fine. Let people enjoy their hobby however they like.

Re: Aerodynamics of Gravel Bikes

#197

Post by skhr0680 »

ben7799 wrote: post #144
jackmott42 wrote: post #128

Earlier quoted context omitted.

You are right I had the gradient off by 10x, sorry that should have been obvious, it has been a while Actual time savings of 1kg of weight reduction: 1 second And personally I've used aeroweenieing to podium in a cat 3 road race, and my wife has set state records and won pro races. You can make fun of fat guys doing a professional job if you like but it isn't just them.

If spending lots of money to win a Cat 3 race and knowing you did it with money and equipment instead of fitness and smarts is OK with you more power to you. But if it means thousands of dollars spent on a race that likely paid This isn't really funny, it's a fundamental problem with cycling as a sport that limits who participates in the sport and hurts the sports ability to find and develop the best riders. It seems…

Keirin bikes need to be built out of approved frames and parts, I’m surprised there isn’t a road racing category with similar rules

Re: Aerodynamics of Gravel Bikes

#198

Post by deebosong »

Melatonic wrote: post #173
bbarn wrote: post #120

Earlier quoted context omitted.

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.

I am not sure this is true - I actually prefer a heavier bike for general use. If I was racing up hills or still doing cyclocross then light as possible would be best (and of course also me being light as possible being the biggest factor). I have ridden a lot of bikes and the ones that "feel" the best have a moderately "heavy" frame designed to be fairly stiff but not crazy stiff (heavy meaning at most the light end…

I'm not that old, or have a super long history with cycling. But out of the handful of bikes I've ridden, I def prefer double-butted steel (over straight-gauge Hi-Ten, straight-gauge 4130, 90's aluminum, modern aluminum, modern steel gravel bikes) whether I'm going all-out, or cruisin. And even between 2 double-butted steel frames from different tubing manufacturers made for the same use-case more or less, they've felt different enough to me. At least that's how I felt after having put the same components on two steel framesets, and putting them both through about 2k miles each. One frameset was definitely more enjoyable, while the other felt lacking to the point where I wished it were the other bike.

I have two relatives who have raced bikes in the past at high levels, and both owned stores. One of them was a stronger racer who didn't care about gear as much. The other was still a heavy hitter, but wasn't as naturally talented, and enjoyed the nuances between components way more. He and I seem to agree on things.

I do know that tire pressure and width make a huge difference in plushness, but I still prefer a springier ride-feel from the steel I like, vs. even a modern steel gravel bike with 42's with lower PSI. I had such high hopes for that ride, but man, it just felt kinda muted and leaden, and I missed my steel road bike.

But yeah everyone will have their personal prefs, subjective interpretations, and theories about what works for them and doesn't. Gimme that springy lightweight steel any day.

Re: Aerodynamics of Gravel Bikes

#199

Post by redler »

prmoustache wrote: post #100
chitowneats wrote: post #66

Earlier quoted context omitted.

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.

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…

Ultimately, it's the engine.

Re: Aerodynamics of Gravel Bikes

#200

Post by gammarator »

shagie wrote: post #59
bbarn wrote: post #50

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'…

> 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

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