Bull

I would be happy to help....did I fail to mention that they fired me????????

Larry Herman

I was there when the BFG engineers told us that their new Comp T/A R1s with the rounded shoulders were designed to roll under to a certain point on the tire, the very edge of the tread, and you could set your tire pressures for that item alone. Some people still swear by that. I wonder how much of that is really applicable to the current tires.

trumperZ06

This may be a little ahead of the info for the novice tire pressure issue but...

Carol Smith has an excellent chapter or two on tires in his "Drive to Win" book. The part on "Tire Graining"... is of special interest. I find this very helpful at the track.


The tire info includes pictures...

David K.

The best advice I ever got on the subject was from Don *** many years ago at The Glen.

He was running Hoosiers at the time and I asked him what pressure he runs, he said 100 pounds and walked away.

993inNC

I have raced/DE'd both front and rear wheel drive cars. Tires have been 14's-19's and have always run the same tire pressures no matter the tires (street, track, R comp's etc) and that pressure has always been 28-32lbs and no more. I have always seen a consistent 6lb increase all four corners and can feel the different pressures as the laps go on.
I have ridden in P-cars with 40lb tire pressures and can't believe how anyone can run such bricks! There shouldn't be that much difference in tire pressures (IMHO) cars are usually rated with tires capable of offering good performance at the usual 30's lb pressures. There may be a little deviation to dial in a handling problem, but running at 28 lbs to start, I can't even imagine starting at 40 lbs......ending up close to 50 lbs hot? thats just insane!

paradisenb

Larry, very nice article. Good beginning to demystifying and very confusing subject.
It would seems to be helpful if you included a method of measuring tire temp as well. Say use a Pyrometer or ?

SundayDriver

Nicely done. Here are some of my suggestions...

I would start by pointing out that everything the car does is via the 4 small contact patches of the tire. There is nothing more important. When setting up the car, you are trying to do 2 basic things with the tires; 1) Maintain the best contact patch and 2) Run a temperatures that match the preformance envelope of the tires (best grip).

Suspension design and alignment have a lot to do with this, but for most people, this can not be changed once you are at the track so all you have to work with is tire pressure. Novices should start (and stick with) what experienced folks suggest with similar cars/tires. Once you can feel the car, then you should experiment - add 2 lbs on one end and feel what the car does. Then the other end. Reduce pressures, etc.

An additional comment about temps - I have seen a lot of folks get really screwed up with temps. A stiff and wide tire, when underinflated tends to take an "S" shape. You often see high center temps with underinflation in such tires. If you reduce pressure and it gets worse, then you know you went the wrong way and need more pressure, not less.

va122

Larry, I don't envy your task but I do admire your ambition. There are so many variables!

Please remind people to bring their tires back up to street pressures when they leave the track (For those who drive to the track.) I'd hate to hear of someone's tire failing.

Please consider elaborating on the importance of camber on dot-r tires vs. street tires. I'm surprised how often people don't realize.

Regarding the S shape on wider tires that are under inflated, I noticed this last weekend when I was using my new Nitto's (315/30/18). Using the rollover method (I wish I had a Pyrometer...) they shoud have had about the right pressure but I feel like they need more camber.

Larry Herman

Yep, it's definitely needs to be a 2 part article. Keep the good suggestions coming. Maybe I keep it as a reference on Rennlist as well.

333pg333

Just digging up an oldie but a goodie thread due to doing some research for upcoming use with some Hoosier Radial slicks. Looking at their website there is some generic info regarding tyre pressures and vehicle weight. They seem pretty high from what I've observed over time. I've not really run on slicks in the past but have heard that most people in rear engined cars are running in the 32-34lb hot range. Of course as this thread illustrates, there are many mitigating circumstances that can influence what pressure to run with.

http://www.bobwoodmantires.com/bwttechtips.php


Vehicle size Recommended
Hot Pressure Cold Pressure
1800-2200 lbs. 34-37+ 26-31
2200-2600 lbs. 35-38+ 27-32
2600-3000 lbs. 37-41+ 27-32
over 3000 lbs. 38-43+ 27-33


My car is a modified 951 which weighs in the around 3000lbs wet with me in it. It's running a bit of aero on KW Race suspension w 800/900lb springs. The tyres will be 265 f and 285 r R80 all round. Any guesses?

kush07

Is this correct? If im running neg. camber how would the inside of the tire be cooler?

NaroEscape

Interesting numbers going about here....
I run a 2000 lb (with me in it) 914 on wide Goodyear slicks. Hot, I try to be at about 24-25 lbs, which means starting cold at about 19-20.

utkinpol

my car is 3300 with me inside, keeping pressures at 37-39psi I got middle section of tire worn out in fronts almost immediately on v700 kumhos and afterward had to keep an eye to keep hot pressures on 32-35psi area where wear was more even. so that 38-43 figure does not make much sense to me. my cold pressure is usually 5-6psi lower than hot pressure.

jrgordonsenior

Those pressures are definitely not for slicks but probably for street tires. Regardless, they're still too high...

I've found Hoosier R80 and R100's to like it right at 30 hot. By comparison, Michelin Blues and Yoko slicks seem to work best around 28 hot. YMMV.....

jrgordonsenior

The inside of race cars with significant neg camber say 3.0 or more run hotter than the middle or outside. The pyrometer doesn't lie, it will tell you how your camber setting are working out...