Re: [CR]Where the rubber meets the road

(Example: Events:Cirque du Cyclisme)

Date: Sun, 6 Apr 2008 12:57:19 -0700 (GMT-07:00)
From: <gpit@ix.netcom.com>
To: CRList <classicrendezvous@bikelist.org>
Subject: Re: [CR]Where the rubber meets the road


Lou,

I read that letter to Car and Driver also. As they pointed out, while the area of the tire contact remains the same (relative to weight and pressure), the shape of the contact patch changes with the tire. So a wider tire means a patch that is longer side to side than front to rear.

Wouldn't the same thing apply to differently shaped bicycle tires? Seems as if the same rules would apply.

I wondered the same thing when reading the letter

Maybe we should devise a skid pad test for bicycle tires similar to the one that CD uses on cars. I've often thought about how much of my sew up tires are actually touching the road. This thought usually occurs to me about halfway through a fast turn in heavy traffic.

Greg Pitman Yucaipa, California USA

Lou wrote:

When looking in the archives, using the search "tire" and "patch", I found 2746 entries. I was looking to see how the issue of the area of the tire patch (rubber meets the road) had been covered. Turns out it has been covered very well. But, in the car world, specifically in this month's Car and Driver, a letter to the editor chastised the magazine for suggesting that wider tires offered more contact area. The writer said that tire patch as measured in area is weight of the vehicle divided by pressure of the tire. I'm not sure whether you have to take into account the number of tires in that equation. I found it interesting in that intuitively, if I'm riding a 700x28 at 100 pounds I would think that I have more tire patch than if riding a 700x20 with 100 pounds. Reading the literature, it appears that only the shape of the tire and perhaps tread deformation have changed, but the amount of the tire patch in area is equal. Still, that does seem odd to me. Lou Deeter, puzzled in Orlando FL USA