Saturday, October 26, 2013

sexy tires



I've been reading and believing Jan Heine's (Editor of Bicycle Quarterly) opinions about tires and tire pressure and rolling resistance and such for some time now. And I've been experimenting with lower and lower air pressure in all my tires - as in, on all my bikes. It takes a lot of time to peel yourself away from what seems to be standard thinking on the topic - essentially, higher air pressure is better and/or faster. I used to always pump up my road bike tires (23 - 25mm wide) to 120psi - the max listed on many tires of this size. And that worked fine and great for me even giving me the sense that I was riding really fast. But part of what Heine has argued is that things are not always as they seem and that just because it feels like you and your bike are hammering along and your bones are chattering over every slight disturbance in the road doesn't actually imply that you're going faster - you really have to time it to know. So he's done a lot of timing and testing. And based on his tests, it turns out that it's only less comfortable to ride high pressure tires and not faster. 

He's even got a chart, a rule of thumb to shoot for based on your tire size and weight to help you determine a more appropriate psi for your own needs. I started with that chart and dropped my road bike tire pressure by about 25psi. Then over a few months gradually dropped even further - an additional 15psi - for the current personal preference for road bike tire psi (get ready to gasp) of 80psi! 

I ride with a regular group of people that I'm calling my control in this experiment. While I cut my psi by 33% they changed nothing as this was all done in secret - until now. And there was no obvious change in our speeds or finishing order at the top of hills or end of rides. Not much of a scientific method employed here I know but it's good enough for me and mostly, more comfortable. 

As for The Mule, well, she runs on fatter tires (50mm wide), but we also enjoyed a similar percentage drop in air pressure and similar "performance" benefits. She's running around 40psi now compared to 65 before. 

Again, back to Heine, it's not just the lower pressure that promotes a better ride but the quality of the tire - it's suppleness. Hard, solid tires, even with little air in them are going to bang all over the place and transmit a lot of that up to the rider. Supple, sexy tires will slip smoothly over the road surface - allowing you to feel the road but not FEEL the road. 

So I took Heine's advice and even bought some tires from him for "Totally 80's" - he sells them in 26mm width (other widths, too) which is just a hair wider than what's generally available out there and adding just that much more cushion of air - they don't call them pneumatic tires for nothing… 


3 comments:

A Midnight Rider said...

I have always set 90-100 psi on my road bike. Closer to 90 only because I was always afraid the tire would pop if I put the recommended 120 psi.

John Romeo Alpha said...

Bicycle Quarterly is slowly but surely changing the way I think about cycling. The tire pressure tests have been very interesting. I look forward to see how your own progress.

mindful mule said...

Midnight, sounds like you're ahead of the curve on this psi issue - 90 seems reasonable.

JRA, yes, BQ has really shifted my perspective, too. I bet it won't be long before I've got a handlebar bag!