Tire sensitivity to inflation pressure
 

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! :D

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 !


:mad0259:


http://i628.photobucket.com/albums/u...ps7608f69d.jpg

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!

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. :-/

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.

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!

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.

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.