[I4MX6]

Originally Posted by gavin

Theres what people like and then theres whats fast.You may want to rethink your approach on tire pressures, heres why.

R-compound tires are built with very stiff sidewalls for two reasons, steering sharpness/response and to maintain the tires contact patch with the ground(which gives the tire more grip). Street tires have much softer sidewalls as they are built for comfort and road compliance but racing on them still require the same 2 characteristics of handling and grip.

For all cars, when the car is in a corner the car will tend to roll to the outside, so does the tire(even more so with a strut suspended car that doesnt have much camber gain). With low pressures the street tires wont have the resistance to stop rolling over onto their sidewalls. SIdewalls have very little grip, you need the tread of the tire in contact with the ground at all times. The solution is to increase the tire pressures to prevent the tire from rolling over in the corners. This will also have the benefit of artificially stiffening the tire(sidewalls) giving crisper steering and better feedback.

Its not uncommon to have new autocrossers arrive to events on street tires. First order of business for them...increase the tire pressures by about 8-10psi. When I was running in the Street Touring classes(street tires above 140 treadwear) I consistently ran 45+psi. This is with 500lb springs and about -3.5deg camber in front(street tires also need much more camber than r-comps...but thats another story).

Gavin

I do run higher pressures but not excessively high. Remember, its not overly warm here, so the tires don't tend to get sticky or stay sticky...well not with regards to street tires. With too high of pressure, the tire breaks loose on some of the soft sand on the track and it looses control and steering abilities. With a little flex, it sort of bobs into the sand a little and plants the weight better. Now I'm not saying run OEM pressures, but I'm not saying max out the tire recommendations either. I'm just saying that street is different then r-comp, and a lot of it has to do with traction offered cause its clear that they both differ in design and stiffness.