Traction and PSI on a 25c tire
08-06-11, 07:30 PM
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SkinnyStrong
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Traction and PSI on a 25c tire
After crashing my bike by sliding out in a turn 2 months ago, I've been wondering a lot about tires, rim widths, and PSI and how they affect traction. I started using 25c tires a while back because of their smooth ride and supposedly lower Crr. For the most part, I've been happy with the switch, however, I find myself wondering if a 25mm tire mounted to a 19mm rim is experiencing deformation when cornering and if that would reduce traction.
Does anyone have any insight on this? If me + bike = 155lbs, which is better - running 80 or 100 PSI? Would it be better to switch back to a 23c tire if I'm more concerned with cornering than rolling resistance?
Does anyone have any insight on this? If me + bike = 155lbs, which is better - running 80 or 100 PSI? Would it be better to switch back to a 23c tire if I'm more concerned with cornering than rolling resistance?
08-06-11, 10:23 PM
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I think it'll end up having more to do with the quality of the tire, the lean angle of the bike, the speed of the bike in the turn, and the surface conditions of the roadway (sand, water, etc...). In 60,000+ miles on a bike, I've never had a tire slide out.
Any tire will experience some deformation when your body weight is on it. The 25's will certainly not be a problem for your size/weight. But neither would a 23. Just make sure it's a good tire. Run it at 100psi or so.
Any tire will experience some deformation when your body weight is on it. The 25's will certainly not be a problem for your size/weight. But neither would a 23. Just make sure it's a good tire. Run it at 100psi or so.
08-06-11, 10:32 PM
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Riding too fast for the road conditions in the turn.
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08-07-11, 07:47 AM
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I've been using Velocity A23 rims with 700x25 tires and sense an improvement in ride and handling. The A23 is 23mm wide and does not deform the tire like a 19mm wide rim. Lower tire pressure is recommended with the wider rim.
However, I would assume that the fall was caused by poor traction. That can happen with any combination of road-bike rim & tire.
However, I would assume that the fall was caused by poor traction. That can happen with any combination of road-bike rim & tire.
08-07-11, 07:59 AM
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Hmm, I routinely run my 25c tires through turns at speeds in excess of 40 mph without any problems. I weigh 165 and run the front at 90 psi and the rear at 100 psi. I'm using Conti GP 4000s on some Williams System 30 rims. Not sure of the rim width though. I suspect your problem was related to factors that exceed the tire width as a contributing factor. Oh and it's my understanding that you don't want rock hard tires set at high pressures while descending. Lower psi gives better traction by my understanding.
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