Originally Posted by ThermionicScott (Post 18847262)

I'm curious (but not willing to do conclusive tests ;)) how low we 150's-lb guys would have to let our 38mm tires get before risking snakebites. I round up a little from what the calculator gives, and that's good for at least a week. Jan Heine lets his 42mm tires get down into the 30's before he worries about pumping them up again.

Originally Posted by noglider (Post 18847536)

The tiredrop chart is a good place...

I'll assume a 35mm tire. Starting with a body weight of 180 lbs, add 30 lbs, and you have 210 lbs of load. The rear will get 126 lbs, which is 57 kg. That gives you a touch more than 50 psi on the rear.

Originally Posted by eschlwc (Post 18847998)

noglider's chart has me inflating my 23c paselas to around 100psi for 190 lbs of total bike weight.

Originally Posted by Chrome Molly (Post 18847915)

While I agree that it is better usually to run lower pressures with 28 plus tires, individual tire construction impacts my decision on pressure as much as size. If you are going to "bend" a tread around objects that introduces a set of stresses that you need confidence the tread can handle. Contis 4000's and most gravel tread tires are strong enough to go low on my roads. Compass tires can't go as low without routinely flatting due to their lack of tread toughness. I love their sidewalls but the tread misses the mark for reliability completely (for my roads at least).

On smoother stuff a 95/105 25c veloflex master runs like butter and is still tough enough mostly.

I spent some time last year comparing 28 and 25 conti 4000s2's. I came to the conclusion that the 28's were great for rail trails and gravel, but the 25's were more "responsive" on most pavement. Both got a thumbs up and knowing the difference on what to use when has proven helpful.

Originally Posted by Salamandrine (Post 18848179)

This sounds really funny to someone who raced in the early 80s. We all used special race tires. Clement Criterium Setas were most popular, and they were much too expensive to ride everyday. I'd guess they cost at least $240 for a set adjusted for inflation. A bit more actually.

Sounds like lots of lip flapping and nothing new. Everyone rode tubulars at about 110 decades ago, perhaps a bit less for training. I pump my current Pasela PT 28 to about 90 figure that's close enough.

Originally Posted by 10 Wheels (Post 18848190)

I used 700 X 18's three times on this track's 100 mile ride.

http://i256.photobucket.com/albums/h...ndy2012184.jpg

Originally Posted by nlerner (Post 18846370)

You'll need to pry my 23mm tires at 140psi from my cold, dead hands.

Originally Posted by OldsCOOL (Post 18848471)

You and me both. Again. :)

Originally Posted by nlerner (Post 18846370)

You'll need to pry my 23mm tires at 140psi from my cold, dead hands.

Originally Posted by jyl (Post 18846180)

Very, very interesting.

I'd think there is a third factor, which is impact resistance - the tire needs to protect the rim and the tube, when you hit a road irregularity that is much larger than the rest. The killer pothole.

With tubulars, you're not worried about protecting the tube against pinch flats. With deep section carbon rims (and a spare set on the following team car) perhaps you're somewhat less worried about damaging the rim.

But I know that if I run my 25 mm clincher tires at 70 psi, I'm prone to get pinch flats. Of course I weigh a lot more than Cancellara . . .

The other consideration that needs to be considered is cornering. At low enough pressure, the tire starts to feel mushy in turns. At even lower pressure, it comes off the rim. I don't know exactly where that constraint lies.

This brings me to another area where I think bike tires could be greatly improved. Rubber compound. Why should an all-out race tire last longer than the race, plus a safety margin? Design for a 500 km life, and you should be able to use really soft compounds that have terrific grip, even in the wet. Race motorcycles wear tires so sticky that they will pick bits of litter from the pavement. And how about the days when the peloton is racing in near freezing weather, e.g. the high mountain stages of the Giro or some of the spring classics?. Snow tires use rubber compounds that stay soft at low temperatures, extreme condition bicycle racing tires could as well.

Bike tire design seems really focused on resistance (rolling, impedance, aero) but a chute slows you down ore than an extra 1% of resistance.

Originally Posted by fender1 (Post 18846435)

I think skepticism is healthy, especially when there is a commercial venture involve. IME, I read what Jan Heine had published awhile back on the same subject and was interested but skeptical as well. Rather than just dismiss it all as marketing hype, I bought some Vittoria Hyper tires and ran them at a lower pressure. I found that for me, what had been reported, was pretty much spot on.

I have since purchased the Compass tires (700x38 with the extra light casing) and have taken to running latex tubes in them as well. I find the ride to be fantastic. I am running the tires 55 psi in the rear and 50 psi in the front and I am 6"1" and 185lbs. I have also noticed (fingers crossed) a steep drop off in the number of flats. Could just be luck of the draw or the tire could be less likely to pick up debris as it deforms and rolls over it more easily. For me the most important part is the comfort. I now find it much less enjoyable to ride bikes with skinny tires and higher pressures. YMMV.

Originally Posted by nlerner (Post 18848496)

Nah, I was just being snarky. My go-fast bike has 38mm Compass tires that I run at no higher than 50 psi.

Originally Posted by cyclotoine (Post 18848826)

I definitely can't get more than 1-2K out of a race tire like a vittoria open corsa, and my new veloflex rear already shows wear at only 300ish kms... so I think the good race tires do wear pretty fast.

Originally Posted by cyclotoine (Post 18848826)

I definitely can't get more than 1-2K out of a race tire like a vittoria open corsa, and my new veloflex rear already shows wear at only 300ish kms... so I think the good race tires do wear pretty fast.

Originally Posted by catgita (Post 18848914)

When Burto came up with the 15% guideline some 35 years ago, that was on a steel drum. It wasn't until 2009 that tests in the real world scientifically demonstrated that higher pressures are not faster. These new tests, also real world using scientific methods, show a significant decrease in performance at higher pressures, which is new, and confirms the earlier results.