ok gang…here’s the question. How much air pressure do we use for a set of zipp 909’s with continen. podium tubular tires on smooth roads such as those in Lake Placid? i’ve had some people say to basically never go beyond 115 psi and some have said 140-150 psi. thanks, dave
Higher pressure mean less rolling resistance. Lower pressure results in more comfort. The roads at Lake Placid are mostly very smooth. Use high pressure.
And by high pressure, use the maximum rating. In most races, I use vittoria clinchers pumped up at their maximum 170 psi rating.
Francois in Montreal
PS: the narrower the tire, the more pressure you should put. Running a 20mm tire at less than 120psi will insure that you will get pinch flats unless you are a featherweight.
LP will be my first IM and some dude recently warned me not to max out the psi at 'cause the tubes will blow when rims heat up from using the brakes too much on the long downhill stretches…
I asked if brakes were those things that you use when you come into T2…
So, is this an IM urban myth - or does this happen with enough regularity on hilly summer courses that it should be considered? Ever happen to any of you that ride at full pressure?
“Race day is a celebration of your training.”
LP will be my first IM and some dude recently warned me not to max out the psi at 'cause the tubes will blow when rims heat up from using the brakes too much on the long downhill stretches…
There is no need for braking anywhere on the Lake Placid course with the exception of a couple of sharp turns in town. With average bike handling skills you can stay stay in the tuck all the way for the long downhill.
The only way a tube will blow due to heat generation while braking is if it was improperly seated to start with. This is more of a problem if riding tubulars since the glue that is directly on the rim (the primary heating surface) will soften. But you would need high air temperature and alpine type descents with many sharp turns requiring repetitive hard braking.
Francois in Montreal
Higher pressure mean less rolling resistance.
Wrong.
Clarify? I thought higher pressure would result in less surface area of the tire in contact with the road - thus less resistance?
Quote Higher pressure mean less rolling resistance.
Wrong.
Very strong argument. You are probably a proponent of the famous theory that says that less inflated tires are less affected by surface roughness. This is an old argument that does not make much physical sense. Do a search on deja.com for endless debates on this topic.
Rolling resistance is due to flexural loss when the tire deforms at the contact patch. Higher pressure means less rolling resistance.
Francois in Montreal
Quote Higher pressure mean less rolling resistance.
Wrong.
Very strong argument. You are probably a proponent of the famous theory that says that less inflated tires are less affected by surface roughness. This is an old argument that does not make much physical sense. Do a search on deja.com for endless debates on this topic.
Rolling resistance is due to flexural loss when the tire deforms at the contact patch. Higher pressure means less rolling resistance.
Francois in Montreal
It’s not an “argument” it’s a word… and you’re “wrong” as well…
It’s not an “argument” it’s a word… and you’re “wrong” as well…
**
Would you mind backing this ‘word’ with an argument ?
I’ll be back on Monday so you have two full days to rewrite new science. Have a good weekend.
Francois in Montreal (well I am actually in New Zealand, so it’s Friday 6pm here)
Done IMLP may times…never was more than I think 120lbs…never really worried about it either…may more things to worry about at IMLP than your PSI on the bike.
Its 112 miles of riding…then you have to do that little run afterward. Go ahead and stick that pressure up at 150psi for some potentially miniscule gain in speed (debatable, as we see in other posts here). What you WILL accomplish from running stupid-high pressure is beating your ass, back, and brain to death. Even an extremely over-generous 5 minute bike split advantage isn’t worth that. DON’T overthink this thing by worrying about all sorts of stuff like this.
Francois, you said you inflate your Vittoria clinchers to 170 psi. What tires are you using? I have Open Corsa’s but don’t recall the max inflation being that high.How high over the rated psi on the sidewall is safe?
*Francois, you said you inflate your Vittoria clinchers to 170 psi. What tires are you using? I have Open Corsa’s but don’t recall the max inflation being that high.How high over the rated psi on the sidewall is safe? *
open corsa CX triathlon, 650x20mm. Rated to 12 bars or just about 170 pounds. You should have no problems going 20-30 psi above the rated pressure. Make sure the tube is properly seated however.
I agree with what others have said. As long as you are not using underinflated tires, speed gains are not that important, and comfort is paramount. However on the smooth Lake Placid pavement, I did not find comfort being a problem.
Francois in Montreal
How do you pinch flat a tubular?