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Aerodynamics of Gravel Bikes

renehersecycles.com

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Re: Aerodynamics of Gravel Bikes

#171

Post by Melatonic »

Lio wrote: post #20
wffurr wrote: post #7

Earlier quoted context omitted.

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

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…

Always made me wonder if taking the swimmers route instead would provide all the same benefits without the cost and look. Shave your whole upper body and go shirtless and you would be pretty damn aero no? Would a skinsuit really improve upon that?

In addition after switching to a Brooks saddle (I tried literally 10s of saddles using the "saddle swap" forum feature on some forums) I now no longer ever want to use padded bike shorts again. Of all the short types the simple padded chamois was my favorite (simple foam - no gel or any other BS) and now I just prefer wearing a pair of synthetic lightweight boxer briefs (no fly) that were designed for hiking originally. There is no padding at all and from day one the brooks was extremely comfortable. It only got more comfortable with time and applies all pressure directly to my sit bones. Every other saddle + padded short (even ones that mostly were on my sit bones) ended up forcing padding into the areas between my sit bones and outside them as my weight compressed the padding. I havent tried their new non leather seats but they seem to operate by a similar tension (a tensioned pliable surface vs a hard plastic shape with padding on top) which results in your weight creating additional space below the sit bones vs filling it with padding.

Re: Aerodynamics of Gravel Bikes

#172

Post by Melatonic »

guywithahat wrote: post #163
Melatonic wrote: post #160

Earlier quoted context omitted.

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…

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

Yeah that sounds about right. Probably people are doing these races on what they already have (fat bikes and mountain bikes) which are obviously not ideal at all. A gravel race shouldnt have any drops or major obstructions so why would you ever want shocks and whatnot?

My opinion is that general use "road" bicycles peaked in the late 1980s and everything we have now are just modern re-inventions of that. A touring bicycle is basically just a gravel bike and also the ideal commuter, grocery getter, and fire road bike. With some "sport touring" bikes being criminally underrated (and also some being more just cheaper road bikes)

Mountain bikes on the other hand have improved tremendously and of course any bike designed for racing (road, cyclocross, etc) has as well.

Re: Aerodynamics of Gravel Bikes

#173

Post by Melatonic »

bbarn wrote: post #120
jackmott42 wrote: post #61

Earlier quoted context omitted.

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 ou…

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 of a steel framed road bike) with extra sturdy rims that are also as light as possible. By far the biggest effects on "feel" however tend to be tires (skinny tires suck) as you can fine tune the pressure to the surface. And of course quality bearings in the BB and hubs can make a huge difference but once you get to a certain middle level they are all good enough.

When the bike gets too light you feel the effect of bumps and terrain much more and it throws the bike around more (especially if you are "getting light" over said bumps). The lightest bikes also tend to be made for racing and can sometimes be on the ultra super stiff end of the spectrum.

Re: Aerodynamics of Gravel Bikes

#174

Post by Melatonic »

ActorNightly wrote: post #148
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.

Rotational inertia matters extremely little for bike feel compared to the overall weight of rider+bike. The torque required to accelerate a wheel by itself without any resistance is minimal.

You have any sources for this? Not trying to call you out but I am generally curious. We know on a car that rotational mass makes a huge difference but a car is continually accelerating and has a constant type of locomotion that is very different than a person riding a bike. In addition the rotational mass of a bicycle wheel is much, much larger diameter comparatively to the total weight of the vehicle (compared to a car) and provides a gyroscopic effect that is critical to the way a bicycle rides and stays upright. I would expect if we could make impossible light bicycle rims and tires the bike would have trouble balancing and feel like shit and also decelerate much faster. But surely there is some middle ground that is ideal?

Re: Aerodynamics of Gravel Bikes

#175

Post by [deleted] »

ben7799 wrote: post #124
jackmott42 wrote: post #61

Earlier quoted context omitted.

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 ou…

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 enthusiast…

[deleted]

Re: Aerodynamics of Gravel Bikes

#176

Post by frenchy »

mauvehaus wrote: post #129
762236 wrote: post #91

Earlier quoted context omitted.

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)

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 do…

It probably is functionally lighter, too. When you walk, your body doesn't slide smoothly along the ground - it wobbles up and down and back and forth. The way most people walk is optimised so that the torso does the least amount of wobbling, but if you add a heavy backpack on that person, it will be moving back-and-forth. Technically, that backpack isn't heavier than it it was in a person's belly, but it does move around more and cost more energy.

Re: Aerodynamics of Gravel Bikes

#177

Post by wl »

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…

While the Trek Émonda is as weight weenie as Trek gets, it can provide an apples-to-apples comparison between aluminum and carbon with basically the same geometry, wheels, bars, tires etc. My experience is that the carbon version feels significantly nicer.

For bikepacking, I'm with you: A traditional steel frame (albeit one with discs), nice wide tires to eat up road chatter, and plenty of places to mount gear.

Re: Aerodynamics of Gravel Bikes

#178

Post by matsemann »

brandmeyer wrote: post #56
matsemann wrote: post #12

Earlier quoted context omitted.

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 ho…

> 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.

I didn't gatekeep or look down on anyone, those I'm talking about is me and my friends. It's just a funny jab at ourselves, spending way too much money and effort on things that ultimately wont matter. At least we have fun doing it :)

I'm a cycle advocate and spend hours a week fighting for infrastructure etc where I live, that I hope helps all kinds of cyclists.

Re: Aerodynamics of Gravel Bikes

#179

Post by matsemann »

ehnto wrote: post #74
matsemann wrote: post #53

Earlier quoted context omitted.

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 i…

Oh I didn't think you were detracting from e-bikes, I just think that an electric gravel bike is worthwhile as it's still a fantastic formfactor for commuting, especially if you still want to use it non-electrically and out on rougher terrain (where rougher can be little bits of dirt or rough road on your commute). I am actually in Australia, which has some surprisingly hilly places!

Ah, I see. I've never tried commuting on an electric, so I just tried to say that my advice from my knowledge only applied to "acoustic" bikes. But great to hear that gravel e-bikes rock as well!

Re: Aerodynamics of Gravel Bikes

#180

Post by seadan83 »

helsinkiandrew wrote: post #54

> 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…

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.
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