Tires for Clydes (Technical)
I had a full blown rear blowout yesterday and had to call the wife to get home. I can't quite figure out how the LBS and I missed the tire wear that I can now see. I was running 26x1.5 kevlar primo comets on the rear of my stratus and when it blew, it went BANG.
Post mortem, the tire had a line of wear at the edge of the kevlar belting and had several spots where the white threads were showing. I'm very glad this happened on a slow section of MUP instead of the 36mph downhill on Saturday.
Anyway, I bought a cheap tire from the LBS to get back on the road (26x1.5 Bontrager slick), but I'm trying to work out the dynamics of choosing a tire for us heavier riders.
Here Goes: Weight on tire = Pressure (lb/in^2) * contact patch (in^2) * some constant
So, let's say there's (340 (my weight) + 50 (bike+stuff) ) *3/4 of weight on the rear tire leading to roughly 300lbs. (Holy Crap!)
300 lbs = pressure * contact patch (we'll assume the constant is same for all tires.)
Now the width of the tire is variable and so is the max pressure so: 300 = pressure * width * length (dropping constants again and treating the patch as rectangular)
So now, I want to minimize the length of the contact patch to drop my rolling resistance.
My 100psi, 1.5 wide comets would come out to a length of 2 inches. Ok, now, looking at some 80 psi, 1.6 inch tires, the length goes to 2.34. And if the 2.5 inch tires at 60 psi will take the length to 2 inches, the same as my primos.
In the end, it looks like comparing the product of width and pressure (more is better for clydes anyway) is a good rule of thumb. Now, I wish I could find some 26x1.7s that went to 120 PSI or ever 100 PSI. :)
What do you think? As an engineer, this is a napkin-level analysis, but it seems valid. Anyone know of any 100PSI tires wider than 1.5in?