Q: “My rear and front tires are showing consistent temp across the tread surface, but I’ve noticed my rear tires are wearing excessively on the outer side. What is causing this and what can I do to address this?”
A: It sounds to me like you may not have enough pressure in your rear tires, and that’s why the sidewalls are “rolling over,” causing excessive wear on the outer side. And since your front and rear tires are showing consistent temp across the tread surface, I’d suggest raising the front pressures an equal amount to what you add to the rear.
A question I have for you is whether the “excessive” wear is really excessive? Since I don’t know your experience level of track driving, I could assume that you’re relatively new to the sport. If that’s the case, what you see as excessive may be normal for high-performance driving. I’d recommend asking around the paddock of the experienced drivers, especially those who use similar tires and a car like yours. They may tell you that what you’re seeing is normal.
If what you’re seeing is truly excessive, then I’d start by raising the pressures by 2-4 psi, and see if it changes. You can then begin to fine-tune from there, looking for the ideal balance between wear and handling grip.
Something else that could be contributing to more wear on the outside of the tire on the rear is not enough negative camber. As an example, if your car has a solid rear axle where you can’t adjust the camber, any amount of high cornering load is going to result in more wear on the outside of the tread than on the front where you likely have some amount of negative camber. If you can’t adjust camber on the rear of your car… well, you just have to live with wearing the rear tires faster than the fronts. That’s the price you pay for the fun of track driving!
Tire construction is another factor. I discovered, with the same alignment, that I got a lot more edge wear with one brand than another. I currently use the Goodyear SC3 on my 718 GT4, running 32#F/34# rear and get very even wear, but that may not apply to an other car.