Low pressure for tubular tires at the track?
02-24-15, 02:05 PM
#26
Senior Member
Don't do that. This is a forum, not a classroom, and even if it were a classroom, you are not qualified here to be a teacher. Make your statements straight up or not at all. If you disagree with a statement, state your disagreement plainly so we can talk about it. There is no qualification for stating truth... but leave the teacher/pupil thing out of it. It's presumptuous and rude.
Yes, radius is the driving factor behind g-forces. That said, we are talking about bike handling... not g-forces. A big person on a neutral bank on a 2g turn will require either bigger tires or higher pressure to keep the bike from squirming under the load of 400+lbs of rider weight at 2g. If the track is underbanked, pulling the same g's with the same person might require lower tire pressure to keep the bike from skipping up track as others have attested. Many crit riders will attest that lower tire pressure is beneficial to cornering grip on an underbanked turn.
In the former situation, the centripetal load is being carried by compression on the tires perpendicular to the track surface, putting a premium on holding tire defomation to a minimum so as to not affect steering. In the latter, centripetal load is being carried by frictional force between the tire tread and the track surface, putting a premium on grip. The net result is, as wens stated, that turn radius and banking are intimately related when talking about tire pressure and bike handling at a particular speed with a particular rider weight.
Yes, radius is the driving factor behind g-forces. That said, we are talking about bike handling... not g-forces. A big person on a neutral bank on a 2g turn will require either bigger tires or higher pressure to keep the bike from squirming under the load of 400+lbs of rider weight at 2g. If the track is underbanked, pulling the same g's with the same person might require lower tire pressure to keep the bike from skipping up track as others have attested. Many crit riders will attest that lower tire pressure is beneficial to cornering grip on an underbanked turn.
In the former situation, the centripetal load is being carried by compression on the tires perpendicular to the track surface, putting a premium on holding tire defomation to a minimum so as to not affect steering. In the latter, centripetal load is being carried by frictional force between the tire tread and the track surface, putting a premium on grip. The net result is, as wens stated, that turn radius and banking are intimately related when talking about tire pressure and bike handling at a particular speed with a particular rider weight.
__________________
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Last edited by Brian Ratliff; 02-24-15 at 02:13 PM.
02-24-15, 02:18 PM
#27
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02-24-15, 02:22 PM
#28
Senior Member
Come on. You've been here for what, 30 seconds and you are already telling people off? Just cuz you're on the internet doesn't mean manners evaporate.
Regardless. Maybe expand on your comment to wens? I'm curious to hear your views on tire pressure at the track, since you sound so sure of yourself in your first reply. Always learning... so, please, respond to the meat of my post and tell me why track banking and turn radius are independent.
Regardless. Maybe expand on your comment to wens? I'm curious to hear your views on tire pressure at the track, since you sound so sure of yourself in your first reply. Always learning... so, please, respond to the meat of my post and tell me why track banking and turn radius are independent.
__________________
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
02-24-15, 02:57 PM
#29
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Yes, radius is the driving factor behind g-forces. That said, we are talking about bike handling... not g-forces. A big person on a neutral bank on a 2g turn will require either bigger tires or higher pressure to keep the bike from squirming under the load of 400+lbs of rider weight at 2g. If the track is underbanked, pulling the same g's with the same person might require lower tire pressure to keep the bike from skipping up track as others have attested. Many crit riders will attest that lower tire pressure is beneficial to cornering grip on an underbanked turn.
In the former situation, the centripetal load is being carried by compression on the tires perpendicular to the track surface, putting a premium on holding tire defomation to a minimum so as to not affect steering. In the latter, centripetal load is being carried by frictional force between the tire tread and the track surface, putting a premium on grip. The net result is, as wens stated, that turn radius and banking are intimately related when talking about tire pressure and bike handling at a particular speed with a particular rider weight.
While I totally agree that most people who ride Encino would do better at lower tire pressure to increase grip- when you start really pushing it on that track- say Sub-12" 200m, you've learned how to counter steer and stay in the lane- what I then start to notice is the lateral forces on the tire. You begin to feel the tire rolling over. You need the high pressure to combat this.. And you learn the bike handling skills required to keep the skipping to a minimum- or maybe you just learn to ride through it better..
02-24-15, 03:21 PM
#30
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I run 160psi at Encino on training wheels and as much as about 180psi on race wheels...
My fastest ever 500m there was a club event where I ran 200psi in my Disc. In the middle of turn 2 on my second lap I bounced and kicked the wheel out. The disc let out a huge thud like a bass drum. It was terrifying and I'm sure cost me time..
Still- dropping PSI does not make you faster- it might make you feel safer, which will likely result in a faster time..
My fastest ever 500m there was a club event where I ran 200psi in my Disc. In the middle of turn 2 on my second lap I bounced and kicked the wheel out. The disc let out a huge thud like a bass drum. It was terrifying and I'm sure cost me time..
Still- dropping PSI does not make you faster- it might make you feel safer, which will likely result in a faster time..
02-24-15, 03:29 PM
#31
Senior Member
... when you start really pushing it on that track- say Sub-12" 200m, you've learned how to counter steer and stay in the lane- what I then start to notice is the lateral forces on the tire. You begin to feel the tire rolling over. You need the high pressure to combat this.. And you learn the bike handling skills required to keep the skipping to a minimum- or maybe you just learn to ride through it better..
One thing I've noticed is skill trumps traction any day. Two g's is two g's, and if your tire start deforming enough under your weight to affect handling, you need to just learn how to let them scrub a bit and be smooth.
__________________
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
02-24-15, 03:29 PM
#32
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I did not make the same mistake when I did my flying 200. Just goes to show that practice is a good thing.
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