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2009 Men's World Time Trial - Tire Choice
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TOPIC: 2009 Men's World Time Trial - Tire Choice

Re: 2009 Men's World Time Trial - Tire Choice 8 years, 2 months ago #25457

  • Neal
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Hello Jack Watts and All,

I suspect wider tires would be worse for cornering in wet weather:

"r.e. those Specialized tubulars, they're fast rolling on rollers--slightly faster than the Bontragers. I should mention though that a friend of mine is blaming them for 3 wet-weather slide-outs. I've used the Bonty's in the rain with good success, I figured the Specialized would be the same, or better, since they're wider. I have limited wet-weather experience with them, but I haven't noticed a problem. The guy who's crashed on them is a pretty good bike handler so I'll admit it concerns me a little. Take that FWIW."

Tire tread wear and contact patch shape

The longer and thinner the contact patch, the less likely a tire will hydroplane. Tires that present the greatest risk are wide, lightly loaded, and small in diameter. Deeper tread dissipates water more easily.

Cheers,

Neal

Re: 2009 Men's World Time Trial - Tire Choice 8 years, 2 months ago #25458

These may be the measurements you remember Kraig:
http://www.sheldonbrown.com/rinard/wheel/index.htm#1
Basically, as spokes were loosened, the wheel didn't significantly change stiffness until some spokes reached "zero" tension.

I also measured deflection elsewhere around the rim, away from the load but not strictly "between the pads", but maybe enough to kind of guess:
http://www.sheldonbrown.com/rinard/wheel/index.htm#4
Since then I've also considered the frame deflection's contribution to closing the gap between the brake pad and rim.

- Do you think the frame's deflection could close (or open!) the gap? Or both?
- What are some things it would it depend on? Chain tension (power output, chain ring size, etc.)? Chain angle (gear choice)?
- Are there "cooperative" combinations of wheel and frame flex?
- How could someone measure and record this interaction live in the field?
Damon Rinard
Senior R&D Engineer
Vroomen.White.Design

Re: 2009 Men's World Time Trial - Tire Choice 8 years, 2 months ago #25459

  • JV
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Neal wrote:
The longer and thinner the contact patch, the less likely a tire will hydroplane. Tires that present the greatest risk are wide, lightly loaded, and small in diameter. Deeper tread dissipates water more easily.


I've always been of the understanding that bicycle road tires were too narrow (too small a contact patch), and speeds were too low for hydroplaning ever to be an issue. I know I've descended on wet roads at over 50mph without hydroplaning (had to brake and/or turn), but I've always been too lazy to do the math to figure out what speed I would have to go to hydroplane.

Re: 2009 Men's World Time Trial - Tire Choice 8 years, 2 months ago #25462

  • kraig
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damon_rinard wrote:
Since then I've also considered the frame deflection's contribution to closing the gap between the brake pad and rim.

- Do you think the frame's deflection could close (or open!) the gap? Or both?
- What are some things it would it depend on? Chain tension (power output, chain ring size, etc.)? Chain angle (gear choice)?
- Are there "cooperative" combinations of wheel and frame flex?
- How could someone measure and record this interaction live in the field?


Good questions, and to be honest I've not really considered them too much...but here's my take:

1)yes.
2)axle EI, bearing placement/design, stay EI, in addition to what you mention - I'm sure there are others.
3) yes, probably
4) if it's simply between the pad deflection you are asking about, well, you could do what i did 8 years ago with a dial indicator and some hose clamps. I'm sure you could spend more money and invest more time to measure more than that.

I think the ultimate design goal when it comes to this stuff is to come up with a frame/wheel/tire combination that maximizes speed under the conditions of interest while subject to a constraint of "don't let stuff rub other stuff".

How does cervelo's "rear triangle design goal" compare to the goal I've proposed?
-kraig

Re: 2009 Men's World Time Trial - Tire Choice 8 years, 2 months ago #25465

kraig wrote:
How does cervelo's "rear triangle design goal" compare to the goal I've proposed?


Ah, but I've said too much already. )
Damon Rinard
Senior R&D Engineer
Vroomen.White.Design
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