Road Geometry Versus Gravel Geo

[.RJ]

Originally Posted by osbk67

There are tradeoffs with every added millimetre of tyre width, both in aerodynamics and weight.

That makes a fundamental assumption that wider tires are less aero - but are they? One of the US gravel racers (Dylan Johnson) found that his 29x2.2 race kings were more aero than narrower tires. Could be unique to his setup, but maybe there's something to be learned there. And then there's zipp's new gravel wheels with a 30mm ID.

So who knows, maybe in 10 years the wheels, frames and other tech will shift what those tradeoffs are... PR at nearly 30mph shows there's already a hell of a lot gained with the new stuff.

[Jaybee]

Originally Posted by lorenbike

And yet they still race with 28-32mm tires at Paris Roubaix.

It would be cool to see if we ever see tires there at 35 or 38mm, besides the sprint track finish I don’t think you’d be giving anything up with wider tires.

Originally Posted by .RJ

I wonder if silca, zipp, jumbo or anyone has done testing to see if a 40+ mm tire would be faster, or if there's any tradeoffs to that.

How often is the final selection at PR determined by a puncture or equipment failure? I have no doubt* that 35+ is the right tire for that course, but pro road is pretty tradition-bound.

*Maybe I should have some doubt- I've never attacked out of a group going 28mph on cobbles and have no idea what that feels like.

[vespasianus]

Originally Posted by Dave

Look at stack and reach only. Adding TT length provides no additional information. My Cervelo Rouvida can be set up as gravel or road. It has flip chips to length the fork and chain stays, but the fit difference is insignificant. Cervelo made the STA slightly more slack, but not enough to justify a zero setback seat post. I have the same stack and reach as my previous road bikes.

An e-bike is a very different thing to me when comparing things. You can get away with things when you have a motor...

[osbk67]

Originally Posted by .RJ

That makes a fundamental assumption that wider tires are less aero - but are they? One of the US gravel racers (Dylan Johnson) found that his 29x2.2 race kings were more aero than narrower tires. Could be unique to his setup, but maybe there's something to be learned there. And then there's zipp's new gravel wheels with a 30mm ID.

So who knows, maybe in 10 years the wheels, frames and other tech will shift what those tradeoffs are... PR at nearly 30mph shows there's already a hell of a lot gained with the new stuff.

Fair point. Product development will continue to improve the aerodynamics of wider tyres through better rims, better tread design, and better tyre/rim integration, although I suspect Dylan Johnson’s testing was against his alternative i. e. 700x45/48 or whatever rather than against 700x30/32 on 55/60mm deep carbon rims…

My main point is that is essentially that Paris-Roubaix is a well-understood and extensively researched and tested event on a defined course. There has been little to stop teams from choosing 700x35s for it for several seasons now, and the reason they’re not, at least to date, isn’t because they haven’t tested for it, much less didn’t think of the idea.