meanwhile

If you're interested in this subject then the google for Jan Heine's blog posts and Bicycle Quarterly artciles about wheel size for randoneur bikes and why he favours 650B. Heine is a NASA Fellow and knows his engineering.

I *think* that 650B and 26 also allow you to shorten trail length for a fork without bad effects, which makes it easier to get a bike that is agile and that can carry significant load at the front without running into handling problems - but I'm working from memory here and the issues are complex.

Thorn, the boutique UK adventure bike maker, and their customers also favour smaller wheels and more rubber. Eg

In praise of riding low pressure tyres fast

..If I was designing an optimally engineered commute bike, then I'd probably go with 26 or even 24 inch wheels, low trail, and dropbars - but the top of the drops would be level with saddle (or even slightly higher) and wider than road racing ones. This would give a great traffic position on the hood and better wrist alignment than flat bars, and the rider would have an easy in the drops position for riding into the wind.

Medic Zero

I'd like to know more about that. Got any links/sources?

cobrabyte

smaller rims = less weight as well, no? A larger rim / narrow tire vs. smaller rim / wider tire. Weight being equal, which would be faster in that scenario?

cobrabyte

Indeed those Thorn bikes look like wonderful touring/commuting machines. I prefer 26" to any other size for touring.

noglider 

Lower weight is faster, and that much is clear. But the smaller diameter means a more acute angle of deflection at the tire patch, which increases rolling resistance. It's complicated, isn't it?

cobrabyte

Quite. Another variable is rider fatigue. Comfort can play a big role in how much faster/farther you can ride as well.

noglider 

I suspect this is true, and it makes a bigger difference when the distance or time spent on the bike is big. That probably explains why 650b tires are popular among randonneurs. They have to live on their bikes for entire days, so a cushy ride reduces fatigue, which indirectly makes them faster.

And to be clear, there's nothing magical about the diameter of 650b (or MTB size or 700c) tires. 650b tires are available in very light weight and wide. That's the magic, not the diameter.

energyandair

Why do you believe this?

My belief is that the primary reason people choose small wheels is that they are small. The bike can then be folded or disassembled into a smaller package for travel or carrying into an apartment and also takes less space when assembled.

A secondary reason is that all else being equal, the bike feels more agile and accelerates faster due primarily to substantially lower rim and tire weight which lowers rotational mass as well as total weight.

A third reason is that there is significantly less wind resistance so, all else being equal (it generally isn't), they are faster on smooth paved surfaces.

As for there being a certain combination of tire diameter and width that feels right. I think its more that there combinations that people become accustomed to and thus feel right to them.

cobrabyte

Agreed. Tire quality is important no matter the wheel size. Of all the changes you can make to a bike, a good quality tire is certainly one that you'll notice significantly.

cyccommute 

The problem is that weight isn't equal. You don't get somethin' for nothin'. Wider tires means more weight. That's life. A Big Apple tire weighs 920g per tire for the cheap version and 710g to 810g for the "performance" version in a 2.15" x26" diameter. It weighs in at a very portly 1100g per tire for the 2.0" 29er (700C) version. A Schwalbe Lugano in a 23mm version with wire bead weighs 325g per tire while the folding version weighs 255g per tire. Two of the Lugano almost weigh less than the a single 26" Big Apple in the best comparison. I'll leave the math for you on the 29er comparison. That's a lot of weight to be pushing around.

Our "friend" above is concerned about rolling resistance which makes only a small contribution to the forces that slow down a bike. You gain a little bit on the rolling resistance but you have to put much more energy into the bike to lift it up hills and to push it into the wind with heavier tires. With heavier anything, really. The same goes for no glider's point. He is right about the angle but it's a minor value. Weight still trumps the rest.

Darth Lefty 

I mash at 12mph. Perhaps this makes me a moral failure in your eyes. But for the purposes of this discussion, it results in me wanting the same gearing as an average person going faster and spinning.

Have you spent time riding a mountain bike set up this way? It's not undergeared at the top end. It is undergeared, though. With the smaller diameter and smoother tires, it's like losing two gears. I don't mind the top end so much, although there are two downhills in my commute I could manage a taller one. What makes it most annoying is that you spend most of your time fiddling between the middle and top ring. The 70" gear range is at 32-11 (the top of the cassette) or 42-15. At the same time the bottom ring has become nearly uselessly low. That's why hybrids ship with higher gearing than mountain bikes despite having bigger wheels. With the bigger wheel and crank, 70 inches is at 38-15 and you can hang out in the middle ring nearly all the time.

noglider 

I feel the difference, and you feel the difference, but lots of people don't.

trailmix

I rarely see rando bikes with 584s. The most common tire size I see on brevets is 622-25.

meanwhile

For RR in general:

MTB Tire analysis - rolling resistance and snakebite resistance


Bicycle Quarterly rolling resistance tests: Spring 2013 - Weight Weenies

Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com


Fast Tires 2013 - Part 2 - Slowtwitch.com

JV's Cycling Blog: The latest tire rolling resistance data is out!!

wide is fast for road
Tech FAQ: Seriously, wider tires have lower rolling resistance than their narrower brethren - VeloNews.com

lower psi can be faster
Technical Q&A with Lennard Zinn - Rolling resistance redux - VeloNews.com

Tyres can make 25% difference on road, drum testing wrong:
Bicycle Quarterly: Performance of Tires | Off The Beaten Path
Rolling Resistance and Tire Pressure | Velochimp

Charts
Tyre Rolling Resistance Data
Mountain Bike Tyre Rolling Resitance
Tire test results from german "bike" magazine

..For inner tubes you should just be able to use google. I haven't built up links there yet. There look to be at least half a dozen decent sources in the first page of this search though:

https://www.google.com/search?client...oe=utf-8&gl=uk

noglider 

I stand corrected. The randonneur bikes I see in bike porn circles often have 650b tires. I guess it doesn't reflect what's really out there on the road.

meanwhile

If you keep looking in bike porn circle, you'll go blind.

Bike Quarterly l-o-v-e 650B, but I suspect reality is different and they're rare - just like low trail bikes.

trailmix

I agree, many of the photographs of classic rando bikes have 584s. FWIW, I run 630-28 on my rando bike.

meanwhile

Probably because they over-pressurize - ie past 15% deflection. If a tyre can't flex because it is rigid, then a flexible carcass doesn't matter. People think this will make the bike faster, but it will actually be slower as well as less comfortable and more puncture prone.

Moral: if you have to be reincarnated as a bike component, then do NOT pick being a tyre!

meanwhile

650B's do look so sweet...

meanwhile

..Unless they're Zaskar conversions, in which case they manage to look badass instead. Which is completely 650B like, but very 90s GT:

spare_wheel

This is like saying almost everyone commutes on mtbs because steel mtb frames are the single most popular base for commuter builds.

spare_wheel

don't forget the brooks saddle, leather grips, bronze bell, and whisky flask holder. i would have to be payed to ride that.

not much wind in an urban environment, jr. there are these things called buildings and sometimes even hills.

as if rando-nerding has anything to do with urban cycling. jan is a nice dude but he is as biased as GP when it comes to cycling fetishes.

in the real world just about any bike that fits reasonably well and has appropriate gearing (or lack of gearing) is "optimal".

trailmix

What is rando-nerding? Sounds fun!

meanwhile

It would be if I'd had drawn an equivalent conclusion from the reported fact. Which I didn't.

meanwhile

You need a Star Trek uniform, a lot of Spanish Fly, and an old French bicycle. I can't tell you more without proof of age - sorry!