Glad you guys are finally studying casing tension. I'm feeling a bit smug over here running a 22mm Attack up front while the trend is to run bulbous 25mm GP TTs and 25-28mm GP4000s. I've said for a while that the current designs of rolling resistance studies are unfairly biased in favor of wider tires. I suspect what you'll find is that construction and compound dominate CRR as the tire is basically acting like a spring. Accordingly, 23, 25, and 28mm tires with identical construction (such as the GP4000S II) should have nearly identical CRR with the nod going to the 23 for all-out speed. The comfort argument then becomes (paraphrasing TomA here) "how far below my optimum PSI do I want to run and what size tire do I need to run in order to not pinch flat?" In other words, if my optimum PSI for rolling resistance purposes on a 23mm tire is 100psi (let's say 90psi and 80psi respectively for 25mm/28mm) but I'm about to ride on really rough roads where I'd like to go 15% below my optimum psi. On a 23mm the resulting 85psi might put me in pinch flat territory whereas I should be safer with 68psi on a 28mm as the larger tire will provide more room in absolute terms for deflection. That's not to say narrower is always better, however. Tires work with rims and rims work with frames. The next logical step is to optimize an entire bike from the tire back.

http://flocycling.blogspot.com/...sion-study-with.html

http://www.flocycling.com/...ng_Tension_Study.pdf

This study was a big success. It has allowed us to prove beyond a reasonable doubt that the following claims are true.

• - Casing tension will rise if tire pressure increases.
• - A linear relationship between tire pressure and casing tension exists.
• - Casing tension will rise if tire size increases and tire pressure remains constant.
• - Casing tension will rise if rim width increases and tire pressure remains constant.

Isn't this basically what we would expect given the rules for thin-walled pressure vessels?

Wish this was my senior year project back in univesity instead of "I know that test doesn't work for measuring a dynamic coefficient, but I want you to run it until it does...."

This study was a big success. It has allowed us to prove beyond a reasonable doubt that the following claims are true.

• - Casing tension will rise if tire pressure increases.
• - A linear relationship between tire pressure and casing tension exists.
• - Casing tension will rise if tire size increases and tire pressure remains constant.
• - Casing tension will rise if rim width increases and tire pressure remains constant.

So does this mean you are going to retract your claim that people should ride 25 mm tires over 23 mm ones since your test methods for Crr in the past was flawed where you put 120 PSI into every tire regardless of size? Looks like most of the Crr benefit you supposedly saw from going to the 25 mm was because you way over pressurized them giving them much higher casing tension.

It has allowed us to prove beyond a reasonable doubt that the following claims are true.