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Old 12-10-2011, 05:01 AM   #1
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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.

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Old 12-10-2011, 05:14 AM   #2
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Front : 235/35/19 32 psi

Rear : 275/30/19 36 psi
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Old 12-10-2011, 05:29 AM   #3
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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.
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Old 12-10-2011, 05:32 AM   #4
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I shoot for 34 front and 36 back when at operating temperature.
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Old 12-10-2011, 05:36 AM   #5
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19" Carrera Classic wheels. PS2 tires. About 1 PSI below OEM spec, cold tire pressures. Nitrogen.
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Old 12-10-2011, 06:24 AM   #6
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front: 225/40-18 @ 32psi
rear: 265/35-18 @ 36psi
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Old 12-10-2011, 06:57 AM   #7
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I run close to factory recommended pressures.
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Old 12-10-2011, 10:24 AM   #8
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32/32. At 29/36 I had very noticeable lift throttle oversteer in any sweeper.
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Old 12-10-2011, 03:55 PM   #9
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225/45/17 32psi cold/37psi hot Front
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Old 12-11-2011, 02:25 AM   #10
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Street only, 32 F / 37 R.
78%N2, 21%O2 mix
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Old 12-11-2011, 05:35 PM   #11
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I run recommended (per the manual) pressures, no problem.
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Old 12-11-2011, 05:50 PM   #12
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Quote:
Originally Posted by vath2001 View Post
Street only, 32 F / 37 R.
78%N2, 21%O2 mix
LOL, I understand it's good to put a little Ar, CO2 and H2O in that mixture.
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Old 12-11-2011, 06:35 PM   #13
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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.
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Old 12-11-2011, 06:59 PM   #14
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Quote:
Originally Posted by san rensho View Post
32/32. At 29/36 I had very noticeable lift throttle oversteer in any sweeper.
Lift throttle oversteer will occur in any turn, especially at the track.
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Old 12-11-2011, 08:55 PM   #15
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Quote:
Originally Posted by 986_c6 View Post
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.
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Old 12-11-2011, 10:23 PM   #16
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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.
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Old 12-12-2011, 04:45 AM   #17
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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.
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Old 12-12-2011, 05:58 AM   #18
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I run 30 all the way around. With coil overs, 36 in th back is just too jarring.
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Old 12-13-2011, 06:03 AM   #19
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Quote:
Originally Posted by vath2001 View Post
Street only, 32 F / 37 R.
78%N2, 21%O2 mix
That's only 99%. What's the last 1%?...hot air?
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Old 12-13-2011, 07:34 AM   #20
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30 / 34..........

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