Care And Feeding of Your Tires
As a rule, you should not exceed the maximum pressure listed on your tire's sidewall, checked cold, for normal driving. The tires on your vehicle may not be original equipment, which could mean that the recommendations in the owner's manual don't match what is on the sidewall. When replacing rubber, try to meet or exceed original equipment standards. Tire quality matters a lot more than width. Load capacity needs to be correct as well. A less than optimally designed wide tire can create a handling nightmare.
On the track we regularly run 50 psi. and more for road-going vehicles. This improves the handling, and prevents the tyre from getting excess wear on the sidewall in extreme conditions.
In our own schools, students are requested to set the pressure at the maximum recommended in the owner's manual. Beyond that, you can do a little fine tuning to create the sort of handling response you prefer. Higher pressures, within reason, are better in dry weather, wet weather, and even snow, unless it is very deep. The reason is that you maximize pressure on the contact patch. More air, or preferably nitrogen if you can find it, also improves fuel economy and reduces the chance of catastrophic tire failure, which generally occurs from heat build-up.
Why nitrogen? We have used it in racing, as they do in aviation, for years now. It does not expand with heat the same way air does.
As stated earlier, always check your tire pressures when they are cold. Be especially diligent before any faster driving or long trips. Do not correct for pressure change due to heat from driving.
Remember that a tire will lose approximately 1psi for every ten degrees Fahrenheit drop in temperature, so adjust accordingly.
Tires degrade due to age, which significantly increases the risk of catastrophic failure. They should be replaced after 5-6 years, even if there is plenty of tread left.
In hotter weather, underinflation is even more dangerous. Usually when the tire fails from heat, the sidewall blows out, and this is a very tricky situation for even a well-trained driver.
Get in the habit of doing a walkaround of your vehicle before driving. you may notice a problem, such as a leak, or a low tire, and save yourself a lot of trouble.