Jake951

I got a tire pyrometer recently and have been taking readings at the track. What I've been looking for is relatively uniform temperatures across the surface of the tires and, for the most part, I'm seeing that. I'm measuring around 175-185 deg F peak in the rear tires after coming off the track, getting out of the car, getting the pyrometer out and taking readings. Assuming the tires have already cooled down a bit by the time I get the readings, this sounds like it's the right range.

However, the pryometer readings also show the front tires typically run 15-20 deg cooler than the rears. I imagine the rear weight bias of the car works the rear tires harder, so that might be the explanation. Is it reasonable to see that much difference between front and rear? My one concern is that the front tires might not be getting into the optimal temperature range if they are that much cooler. Thoughts?

RedRSA

Kudos; taking tire temps is a great idea; in fact, some of the more meaningful data you can collect at the track because it reveals appropriateness of your alignment, effectiveness of your grip, and is also a good indicator of how you're driving. These readings do not stand alone, however, and must be factored into the bigger picture of lap times, handling and tire wear. Here are a few data points to help you out.

First and most important, taking proper tire temps requires two people and must be done smokin' hot. I mean after a few very clean and fast laps dive into the pits, stop immediately by your crew, and watch the smoke pour from your front rotors while they quickly take the temps, kind of hot. What you are trying to gather is the running temp at the inside, center and outside, and the tire temp spreads across the surface very quickly. Sorry, but by the time you've driven to the pits and do it yourself you're wasting your time - no wonder the temps are fairly even.

The are many variables, including track, car model, tire brand, tire compound, etc. that affect optimal alignment and temp readings. In general, I've heard that a linear 10-20 degree spread from inside to outside is ideal. The high temps should be in the tires sweet spot for max grip; as I recall for Hoosiers that is in the 200-220 degree range. Front temps on a 911 are traditionally suboptimal; the temps are lower than ideal and the spread can be disappointingly wide, with differences between right and left, as well.

Also note that the tip of the pyrometer needs to be pressed deeply into the carcass of the tire, and use a routine sequence starting with the left side of the car for clockwise circuits. Turning the wheel to make the back of the tire more accessible is appreciated by the crew - just make sure they are clear of the tires first, such as when they work their way to the back tires.

Jake951

Yeah, I realize what I really need is a pit crew to help me out with taking readings, but I'm a one-man show (this is at DE events). I was hoping that even if the absolute temperature readings are off the true hot temperatures, which I'm sure they are, the relative spreads might still hold. I guess you're saying no?

RedRSA

Waiting till you're in the paddock is okay for taking pressures, realizing that they have probably dropped about 0.5 to 1.0 psi from hot after cool down lap. However, not acceptable for tire temps, they must be taken very hot and very quickly. Experience and practice helps, as does the type of pyrometer with memory of each position/temp.

Like you, I participate in DE's and like you I am a one-man show. That is what friends are for; I'll take your temps, you take mine, kind of thing that benefits both.

I always seem to run out of time, but I would like to get one set of temp readings at each event. Valuable data.