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Aerodynamics of Gravel Bikes

renehersecycles.com

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Re: Aerodynamics of Gravel Bikes

#161

Post by Melatonic »

gergely wrote: post #78
jackmott42 wrote: post #73

Earlier quoted context omitted.

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

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

Re: Aerodynamics of Gravel Bikes

#162

Post by newaccount74 »

prmoustache wrote: post #94
gergely wrote: post #92

Earlier quoted context omitted.

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.

Aero also helps at 25 or 30kph. It is quite easy to check out actually on a road bike. Ride at a steady pace without pushing hard, hands on top, then put your hands in the hoods of the brake lever, elbows at 90° without pushing more, you will gain easily 1kph just by changing position. More if it is windy.

I assume the poster meant aerodynamic optimisation of the bike itself (eg. aero wheels, aero saddle post, etc).

Riding position obviously makes a huge difference.

Re: Aerodynamics of Gravel Bikes

#163

Post by guywithahat »

Melatonic wrote: post #160
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'…

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

Re: Aerodynamics of Gravel Bikes

#164

Post by Melatonic »

prmoustache wrote: post #103
gergely wrote: post #99

Earlier quoted context omitted.

But crit races are not like coming down from Stelvio kind of speed where nervousness counts. Crit races are exactly like cx races but on asphalt or at least where I'm in Europe ;)

I rode my cyclocross bike in the Swiss alps for months while waiting for my custom road bike. It was perfectly fine descending mountain passes. As I said, that so called nervousness is overstated because people overthink it. BB height matter but for the most part we intuitively and inconsciously accounts for it and adapt. Also the difference is minute, from a 5 mm to 15mm. It is not like we switch from a road to a ta…

A lot of people do not size their cross bike right - they ride a top tube length that is too short. Maybe this also helps with tight turning radius (which could be an advantage during a cross race).

Re: Aerodynamics of Gravel Bikes

#165

Post by Melatonic »

criddell wrote: post #29
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 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…

"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.

Re: Aerodynamics of Gravel Bikes

#166

Post by Melatonic »

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…

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!

Re: Aerodynamics of Gravel Bikes

#167

Post by Melatonic »

Steltek wrote: post #19
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…

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 expectin…

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.

Re: Aerodynamics of Gravel Bikes

#168

Post by Melatonic »

qwertox wrote: post #58

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…

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.

Re: Aerodynamics of Gravel Bikes

#169

Post by Melatonic »

grzes wrote: post #136

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

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.

Re: Aerodynamics of Gravel Bikes

#170

Post by scott_w »

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…

That’s been tested and it’s objectively not true from a physics perspective.

That said, weight isn’t as big a factor until you go uphill, which is why you’re seeing the trend to more aero instead of lighter weight bikes.

What you’re describing, however, is the simple effect of eating food replenishing your energy.

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