What tire pressures do you run? (street)
 

I've been fooling around with tire pressures and now I'm kind of confused. What tire pressures front/rear are folks using for general street driving? I'm trying to get sort of a balanced, nimble feeling and the stock pressures make my car understeer.

When I read some old posts I get conflicting information about whether the front/rear bias gives more or less understeer.

Front : 235/35/19 32 psi

Rear : 275/30/19 36 psi

I agree, 29 in the front is too low in my opinion, I run 17 inch tires and like between 31 and 32 in the front and 36 in the back.

I shoot for 34 front and 36 back when at operating temperature.

19" Carrera Classic wheels. PS2 tires. About 1 PSI below OEM spec, cold tire pressures. Nitrogen.

front: 225/40-18 @ 32psi
rear: 265/35-18 @ 36psi

I run close to factory recommended pressures.

32/32. At 29/36 I had very noticeable lift throttle oversteer in any sweeper.

Street
225/45/17 29psi Front
255/40/17 33psi Rear
Hankook Ventus R-S3

Track
225/45/17 32psi cold/37psi hot Front
255/40/17 33psi cold/38psi hot Rear
Nitto NT-01

Street only, 32 F / 37 R.
78%N2, 21%O2 mix

I run recommended (per the manual) pressures, no problem.

LOL, I understand it's good to put a little Ar, CO2 and H2O in that mixture.

I try to run factory spec but once the tire warms up tire pressure goes up signficantly during summer months. Took a long drive to Flagstaff last Sept from the Bay Area and had to drive thourgh Mojave desrt. Saw my tire pressure go up as much as 4 psi front and rear. Winter months seems it doesn't go up as much.

Now I run 30 up front and 34 at the rear.

Lift throttle oversteer will occur in any turn, especially at the track.

+1 Lifting in the middle of a fast sweeper is like pressing the ejection button. It works every time.

Regarding the OP, I usually run 32/32 cold on the street. Running 29 up front will add a little ride comfort but not much noticeable change in handling.

Maybe I'm just unconsciously compensating with steering for trail throttle oversteer, but it is very pronounced with 29/36 psi and essentially non existent when I run even pressures.

Thanks for the replies. I tried 35 all the way around but the car rode too rough over cracked pavement. What I'm trying to understand is how the front/rear bias changes understeer. I always thought a low front tire pressure was kind of a bandaid to create understeer because the car companies felt that was best for their customers. Probably they arre right, too. I think Corvairs had unbelievable tire pressures - something like 15 psi on the front and 26 on the rear.

When I bought my car a year ago I was impressed with the neutral steering and when I checked the tire pressures, the previous owner had a reverse bias with roughly 35/29. I would have kept it that way but one of the fronts was cupped and so I bought new fronts only. Unfortunately I picked a "grand touring" tire instead of a sports car tire. I'm pretty sure that is the root of my handling issues. I test drove a newish Miata and it steered ten times as good as my Boxster. The new rear tires I just put on are the same brand (Kumho) but they are more of a sports car tire. I think I need to get something better for the front.

I run 30 all the way around. With coil overs, 36 in th back is just too jarring.

That's only 99%. What's the last 1%?...hot air? :D

30 / 34..........

See my post above. Ar, CO2, water.

Dale - exactly which make/model and size of tires do you have front/rear?

Increasing the front tire width ~20mm beyond stock is a common approach to reducing the interrent understeer in a Boxster. If you are still running the stock tire widths front and rear, then no amount of tire pressure adjustment is likely to fully or completely address the issue.

Addititionally, a mis-match of tires from front to rear (stickier tires in rear and not so sticky tires in front) could also exacerbate the understeer problem beyond the ability of any tire pressure adjustment to address.

Let us know what tires you have installed so we can help pinpoint a good solution.

Tires are stock size 18's for a 2000 S. Kuhmo's front & rear but different types. Fronts are Ecsta LS Platinum and rears are Ecsta LE Sport. I think the fronts are killing my steering response.

Oh my, two completely different classes of tires. No amount of fiddling with tire pressures can fix this. I would lose those Platinums pronto and put LE Sport 225/40/18s on the front. It will transform your car.

Vaporized Tiger's Blood..... Winning

I think we've found your problem.

Looks like that's the culprit. It's like only putting snow tires on the driving wheels, they'll grip while the other two slip. The same would happen even on dry pavement with two different types of tire.

Yep! Well beyond the range of a tire pressure adjustment.