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Relatedly: if you and your bicycle weigh 200 pounds, and your tires are inflated to 90 psi (a very reasonable pressure for a road bike; racers run much skinnier higher pressure tires), your total contact patch is a little over 2 square inches. Think about that the next time you’re watching somebody fly down a descent going 45mph or more. That’s not a lot of rubber keeping you on course.

As an added bonus, you can basically ignore sidewall stiffness for bicycle tires.






All the leet roadies are running 25mm tires now. You get jibed for running 23's on an older bike with brakes that don't open enough.

25 is already oldschool. Newest aero rims are designed for 30+, running absurdly low pressures with hookless tubeless tires.

I guess I'm way out of date. I remember hearing that people who ride e.g. PBP run way wider tires than normal road racers because of the road conditions, but I didn't realize that the mainstream road racers were running that wide now.

Also: hookless? Like they got rid of in, like, the '70s or '80s? My beater road bike (that's older than I am) has 630mm hookless rims, and I got a discount because of it.

Are the new ones hell to change tires on? Changing tires on that bike is the most miserable bike maintenance task I've done. And I've done most anything short of a headset or suspension fork rebuild.


Well, a lot of this is driven by the gravel racing gang... the people partying at gravel events are already happy running 40+mm width, or MTB tires, on very wide rims. But there's also a growing segment of people who have figured out that you can have a bike that's a little bit more comfortable off pavement by going wider, without totally compromising speed on the pavement, and it also makes tubeless less likely to blow up in your face.

Zipp and ENVE seem to be in some kind of internal width arms race with the release of the Zipp 303-S, and the ENVE SES AR series rims. I was exaggerating a little bit :) You'll still find many, many road bikes with disc brakes maxing out with clearance for 32mm width, but that's an improvement over their rim brake cousins. But look around in the growing "all-road" segment and you'll find wider tire clearances on road geometry frames showing up.

I am unsure if this hookless is the same hookless that is from way back in the day. With the way things go in the bike industry (cyclically, no pun intended), I wouldn't be surprised if it were.


That was informative; thank you. I’ve been pretty out of touch with the cutting edge for a while.

> I am unsure if this hookless is the same hookless that is from way back in the day. With the way things go in the bike industry (cyclically, no pun intended), I wouldn't be surprised if it were.

I’m sure they’re holding way tighter tolerances in manufacturing now than they were back then at the very least. Probably more on the tire side than the rim side.

You used to have to get matched sets of V-belts for multi-belt applications, table saws being a common one.

Nowadays, people mostly accept that the tolerances are tight enough that you don’t need to do that, at least for the lighter-duty uses.


I’ve gone from 700x25 to 700x35 to 650x42 and I’m never going back. The wider tires are no slower, and a hell of a lot more comfortable. That may be because I am in a land where bad chipseal is good pavement, but even on Germany’s smoooooth roads, they still fly.

The new tubeless rims are different than the old ones, and There’s a lot that went into reducing the variance in the rim the rim / tire interface.


Wow, I just road ride for leisure on my own, don't know any racers/university types, and my tires are 5 years old 19mm on an old carbon frame. I'm way out of current trends.

My ass hurts just reading that. I bike toured about 7000 miles on 622x28ish tires, and I can't even imagine riding 19mm tires on anything other than completely immaculate pavement (or maybe a velodrome? What do they run?).

Think of it as a free muscle toning workout for your ass. I miss the days of 8 miles a day bike commute on thin road tyres on bumpy roads and paths.

You prompted me to look at new tires. $50-60 per tire! I am really getting old...

I think the velodrome gang have stuck to 23mm as road bikes move to 28?

With ideal friction assumptions, the contact area doesn't matter. The friction force is determined by the normal force (weight) and the coefficient of static friction.



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