Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Aerodynamics of Gravel Bikes

renehersecycles.com

Post reply on HN
Print view View original

131–140 of 211 posts

Re: Aerodynamics of Gravel Bikes

#131

Post by ben7799 »

wyre wrote: post #37
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 i…

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.

Re: Aerodynamics of Gravel Bikes

#132

Post by pharmakom »

762236 wrote: post #88
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.

Where are the supposed alternative people with scientific methods?

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

Re: Aerodynamics of Gravel Bikes

#133

Post by ben7799 »

nradov wrote: post #16
jrf6 wrote: post #10

Earlier quoted context omitted.

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?

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 f…

For sure, and the bike industry tricks huge numbers of slow people into vastly overspending on their bikes with no real benefit.

They basically never test these aero bike gadgets on a rider.

Aero helmets and clothes are probably the only ones that get tested on riders in a valid way.

Re: Aerodynamics of Gravel Bikes

#134

Post by FastEatSlow »

wrycoder wrote: post #101
prmoustache wrote: post #42

Earlier quoted context omitted.

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.

Would you happen to know the age at which Dutch commuters (shopping) start to give up cycling? Do people regularly cycle past 90?

The oldest age I've found is 75, and they still rode 2x per week in 2011. http://www.aviewfromthecyclepath.com/2011/02/who-cycles-in-n...

Re: Aerodynamics of Gravel Bikes

#135

Post by darkerside »

fnbr wrote: post #122
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.

They’re not- 300W of effort is 300W of effort, it doesn’t have a bigger impact if the bike is heavier or not.

I wonder if that's really true on hills. Most people ride hills with more effort, pushing down on one pedal at a time. The bike speeds up and slows down much more with each pedal stroke. Compare to the flats where you have a smooth stroke and very consistent output.

I could see all the mini accelerations adding up to a much larger energy expenditure than would be indicated by a spherical cow in a vacuum.

Re: Aerodynamics of Gravel Bikes

#136

Post by grzes »

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

Re: Aerodynamics of Gravel Bikes

#137

Post by toss1 »

vikingerik wrote: post #115
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 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 thought…

One racecourse I know about that has both running and bicycle races is the Mt Washington Auto Road in New Hampshire USA. It is the tallest mountain east of the continent. The top is at 6288ft/1917m above sea level. The road is 7.6 miles / 12.2 km long and the climb is 4650 vertical feet / 1420m.

The footrace has been run since 1936 and the bicycle race since 1973. The road used to be paved only half way and gravel the rest, but it is now largely paved.

Now, the Men's bicycle record is 0:50:38 (2022) and the women's record is 58:14 (2000). The running race records are 0:56:41 (2004) and 1:09:25 (2012).

So, pretty clearly, even at a 12% grade, the bicycle still has an advantage. I'd say this is still true even though the bicycle race consistently attracts US Cycling Team and other international class competitors, and the running race seems to less frequently attract that caliber.

[0] https://en.wikipedia.org/wiki/Mount_Washington_Road_Race

[1] https://en.wikipedia.org/wiki/Mount_Washington_Auto_Road_Bic...

Re: Aerodynamics of Gravel Bikes

#138

Post by cheeze »

lm28469 wrote: post #68
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…

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

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)

Re: Aerodynamics of Gravel Bikes

#139

Post by vikingerik »

toss1 wrote: post #137
vikingerik wrote: post #115

Earlier quoted context omitted.

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 thought…

One racecourse I know about that has both running and bicycle races is the Mt Washington Auto Road in New Hampshire USA. It is the tallest mountain east of the continent. The top is at 6288ft/1917m above sea level. The road is 7.6 miles / 12.2 km long and the climb is 4650 vertical feet / 1420m. The footrace has been run since 1936 and the bicycle race since 1973. The road used to be paved only half way and gravel th…

Very interesting information, thanks. The sibling comment pointed out that the parent probably meant 40 minutes for 1km of elevation gain, not linear distance, which makes sense too.

Maybe I'm just trying to justify my own struggles where it's faster to walk the bike up any significant grade :)

Re: Aerodynamics of Gravel Bikes

#140

Post by smadge »

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…

Could this be true for walking but not for biking? The human body is adapted to carrying its own weight while walking, but not adapted to carrying significant weight on the back. But while biking the body is supported by the bike, and largely only the legs move.
Post reply on HN