Tire pressure

[jhilb]

What's everyone running for tire pressure? 315's rear, 275 (I think) front.

[Real time recon]

Most are running in the 20s on PSI >>> http://www.ffcars.com/forums/17-factory-five-roadsters/551153-tire-pressure.html

[VRaptor SpeedWorks, LLC]

We normally run around 26psi front and rear.

[crash]

It really depends on the specific tire. We run two different brands of tires right now. Sometimes both kinds during the same weekend of racing. One tire likes around 28 psi, while the other works much better at 34 psi. Point is that you aren't going to have a hard and fast rule for a given tire size as it more depends upon how the tire is constructed and what you are doing with it. What I can say is that you are probably going to want to stay somewhere between 21-35 psi. Tire wear, and if you are using them under extreme conditions, then tire temperature across the face of the tire will really help you determine the proper tire pressure to run.

[mikeinatlanta]

It really depends on the specific tire. We run two different brands of tires right now. Sometimes both kinds during the same weekend of racing. One tire likes around 28 psi, while the other works much better at 34 psi. Point is that you aren't going to have a hard and fast rule for a given tire size as it more depends upon how the tire is constructed and what you are doing with it. What I can say is that you are probably going to want to stay somewhere between 21-35 psi. Tire wear, and if you are using them under extreme conditions, then tire temperature across the face of the tire will really help you determine the proper tire pressure to run.

Really surprised at the 34 on a car that light. What tire size, weight on wheel, and why do you think it likes that much? Not challenging your number, just curious what you have learned.

[jhilb]

I went with 27 front, 28 read. Figure that seems about right.

[crash]

It's tire construction. We are currently running enough down force to develop 1.7-1.8 Gs in the corners. We run a 345 rear and a 305 front. Hankooks and Toyos. No tire has ever been in the 30s for us...until the Toyos. We were actually running them quite a bit too low and experiencing big gaps in lap times between the two tires. We called a tech at Toyo and they suggested upping the tire pressure. We did so and the delta decreased significantly between the two brands of tires. But again, it also really has a lot to do with what you are doing with the tire as well. If you are looking for maximum lap times it is far different from cruising and wanting a comfortable ride.

[mikeinatlanta]

It's tire construction. We are currently running enough down force to develop 1.7-1.8 Gs in the corners. We run a 345 rear and a 305 front. Hankooks and Toyos. No tire has ever been in the 30s for us...until the Toyos. We were actually running them quite a bit too low and experiencing big gaps in lap times between the two tires. We called a tech at Toyo and they suggested upping the tire pressure. We did so and the delta decreased significantly between the two brands of tires. But again, it also really has a lot to do with what you are doing with the tire as well. If you are looking for maximum lap times it is far different from cruising and wanting a comfortable ride.

Was interested in the track perspective, not street. It's funny how often common knowledge is wrong. Very interesting, thanks.

[mlkwd1]

Was interested in the track perspective, not street. It's funny how often common knowledge is wrong. Very interesting, thanks.

I am running Toyo R888s 335 rear and 275 front. I was at Sema last year and the Toyo Rep suggested (after being non-committal) starting at 22-24 and check the side arrows to see how far I was rolling over on the track. I ran the car once this year in April so the track was fairly cool. At 24 all around I was rolling over to the edge of the triangle tips. Tire wear looked good. I admit that the car is far better than I am and I am not sure how hard it can be pushed and if it will roll further. With some track time and a warmer track, I think 22 is a closer pressure to where the car will work.

With that said, I replaced the springs with softer springs, added a sway front bar, corrected horrific bump steer front and rear, put as much caster in the car as possible, a set of custom Bilstein shocks, 14 inch brakes with racing pads and lowered the car to about 3.5 inches. Who know what it will feel like next time out.

[crash]

I am running Toyo R888s 335 rear and 275 front. I was at Sema last year and the Toyo Rep suggested (after being non-committal) starting at 22-24 and check the side arrows to see how far I was rolling over on the track. I ran the car once this year in April so the track was fairly cool. At 24 all around I was rolling over to the edge of the triangle tips. Tire wear looked good. I admit that the car is far better than I am and I am not sure how hard it can be pushed and if it will roll further. With some track time and a warmer track, I think 22 is a closer pressure to where the car will work.

With that said, I replaced the springs with softer springs, added a sway front bar, corrected horrific bump steer front and rear, put as much caster in the car as possible, a set of custom Bilstein shocks, 14 inch brakes with racing pads and lowered the car to about 3.5 inches. Who know what it will feel like next time out.

Remember, there are starting pressures and then operating pressures. Our pressures will come up 4-6 pounds from cold to hot. I was speaking of hot pressures. Still, 22 sounds pretty low, but we do not run the 888s. We run the R1 which is the racing slick. Again, likely a very different tire construction.

[mlkwd1]

Remember, there are starting pressures and then operating pressures. Our pressures will come up 4-6 pounds from cold to hot. I was speaking of hot pressures. Still, 22 sounds pretty low, but we do not run the 888s. We run the R1 which is the racing slick. Again, likely a very different tire construction.

Crash, you are correct. My pressures went from 22 cold to 26 when hot. It was a relatively cool day so on a very hot track they will likely be high and act completely different. Additionally my track experience is far different than some who are much more aggressive. 22 may not be a good starting point if you are pushing the limit.


Michael