Tire sensitivity to inflation pressure

[babydriver]

I've noticed on my FR-S that relatively small differences in tire inflation seem to make pretty big differences in handling. Recently, I purchased a racing tire gauge that is accurate to 0.1 lbs of air pressure. Setting the inflation to 35 psi (all within a tenth of a pound) seemed to make a big difference. I was able to take my favorite wide sweeping curve at 80 mph with ease, a full 5-10 mph faster than previously. I could probably go faster, but don't want a big fat ticket!

I don't necessarily know if the factory recommendation is ideal for handling. I am not that interested in drifting, so I'd like to keep the rear end under tight control in the curves. Any experiences out there with changing this factor?

Thanks!

[RFB]

Originally Posted by babydriver

I've noticed on my FR-S that relatively small differences in tire inflation seem to make pretty big differences in handling. Recently, I purchased a racing tire gauge that is accurate to 0.1 lbs of air pressure. Setting the inflation to 35 psi (all within a tenth of a pound) seemed to make a big difference. I was able to take my favorite wide sweeping curve at 80 mph with ease, a full 5-10 mph faster than previously. I could probably go faster, but don't want a big fat ticket!

I don't necessarily know if the factory recommendation is ideal for handling. I am not that interested in drifting, so I'd like to keep the rear end under tight control in the curves. Any experiences out there with changing this factor?

Thanks!

I have found that -
Any change in pressure ratio between the front and rear alters handling, and I experiment making rear or front harder depending on the track, to balance the oversteer - understeer. (Harder rear than front - more oversteer, etc.). The amount of traction increases as the tire gets softer and gives more road contact.


Seems just after several laps of adjustment, just when I get it right for the track, temp, etc., the conditions change !

[Tcoat]

On here someplace is a 500 post debate on tire pressures. Not sure how valuable it would be though as I am pretty sure it delves in quantum physics a few time!

[NWFRS]

The ONLY time I've ever been aware of my tire pressure was after a service on my '03 Suzuki SV1000S. A local dealership who I won't name (Mount Baker Moto Sports) had overfilled both tires. I felt like I was going to tip over and fall off at any moment. Pulled over after about two blocks and checked the tires...50psi!!! I let some air out and went about my day, feeling fortunate to be alive. F***ing scary. :-/

[jvincent]

Originally Posted by babydriver

I don't necessarily know if the factory recommendation is ideal for handling. I am not that interested in drifting, so I'd like to keep the rear end under tight control in the curves. Any experiences out there with changing this factor?

Tire pressure, and more specifically HOT tire pressure, definitely has an impact on the track.

There's no hard and fast rule though since it it track/tire/driver preference dependent.

When I switched from the stock tires to Hankook V12's I just picked a HOT pressure as a starting point and then experimented up/down from there.

[CatDaddysBBQ]

I found that 34-36psi was good for the oem tires. Less than that and you'd roll the sidewalls in autoX, and anything over 38 was like a plastic tire and would understeer like on ice.

This year I've upgraded and I get to test and adjust to find a new good area. Fun "problem" to have!

[babydriver]

I tried using 35 psi on the front and 34 psi on the back tires to see if I could increase traction. Did not like it at all! The steering became unpredictable and a little scary with the rear end having a mind of its own. I put them all back to 35 psi for now. The car returned to going where I point it without drama.

I plan to try 34 psi on all four tires and see how that works.

[wparsons]

I have a feeling it's more in your head than anything. Altering pressure by a couple psi isn't going to give you enough more grip to go 5-10mph through a corner.

Same goes for the car handling wildly different by changing pressure by 1psi at one end.

Pressure is definitely a valuable tuning aid, but you need more than a 1psi difference to make a big difference.

[vroom4]

Originally Posted by wparsons

I have a feeling it's more in your head than anything. Altering pressure by a couple psi isn't going to give you enough more grip to go 5-10mph through a corner.

Same goes for the car handling wildly different by changing pressure by 1psi at one end.

Pressure is definitely a valuable tuning aid, but you need more than a 1psi difference to make a big difference.

No doubt. 3-4 psi maybe. 1 psi, no.