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Old 10-31-2006, 05:13 AM   #1
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Tire pressure for best cornering performance?

I had the tires too low when bought the car , it was 28 psi, I didnt know , I used the car like this for a month, handling was actually good, I drifted the rear a bit when pushing it , but it felt quite good, but my tires were wearing out quick.

So now I put 30psi on the front and 36 in the rear (as recommended by the door sticker ) and dont like the handling at all, I lost the confidence to drive it agressively on the twisties.

Whats the best tire pressure to have the best cornering performance?
Boxster Base 2005, 18' Pilot Sport PS2's tires.

I drive in the wet and in the dry, same pressure for wet driving than dry?
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Old 10-31-2006, 05:17 AM   #2
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I use the pressure recommended in the US of 31 front and 37 rear in an '06 with PS2s. The handling seems great to me.
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Old 10-31-2006, 05:53 AM   #3
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Hi,

Largely a matter of taste, but Porsche designed the suspension/tires to work together and to run at these pressures. My biggest concern over running too low a pressure would be damaging a Rim on a pothole, curb, and the like...

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Old 10-31-2006, 06:26 AM   #4
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stay on top of pressures, its easy to dent wheels if the pressure falls too low. Check them every time you get your tank filled or sooner if you drive often. I noticed I lose about a pound of pressure between refueling. Also buy a decent pressure gauge like a LongAcre ($30 ebay) and make sure it will read past 30 psi.
I have 18"/Pirelli Snowsports (decided to run winter tires early) 33 front 36 rear.
Not what I would really like but the roads are too rough in these parts to go below that and afterall they're winter tires.
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Old 10-31-2006, 06:45 AM   #5
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I bought a little cheap digital tire gauge that SEEMS to work a million times better than my crappy pneumatic one. Are these types of gauges accurate? They sure seem to be.
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Old 10-31-2006, 07:05 AM   #6
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motoadve:
"So now I put 30psi on the front and 36 in the rear (as recommended by the door sticker ) and dont like the handling at all, I lost the confidence to drive it agressively on the twisties."


What speciffically don't you like about the handling?
Perhaps you've driven the tires underinflated for so long (especially the rear ones) that they have worn out unevenly in some areas. That may be causing the undesirable handling now. Just guessing.

Z.
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Old 10-31-2006, 08:06 AM   #7
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cheap air pressure gauges are garbage. I've seen differences of as much two pounds. I'd check with my longacre and then test the el cheapo I bought at pepboys during autocross events. The gauges on those portable inflators are just as bad.
Low pressures are more desireable because you know they cut out understeer. If the car has more understeer people will take turns at much slower speeds. That's what the car makers want, they don't like drivers being daring in their cars and ramming a wall or highway divider. I don't think the recommended pressures have anything to do with optimum performance.
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Old 10-31-2006, 08:52 AM   #8
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Ya, Come to think of it I remember watching some tuning show talking about how manufacturers design cars to understeer (Acura RSX was the test car). So the tuners had to put a whole new suspension and race wheels and engine mods, etc to get it race ready. They put it to understeer because its safer than oversteering I guess, at least a novice can keep an understeering car under controll.
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Old 10-31-2006, 09:47 AM   #9
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What the F, i thought factory recommended was 25 in front and 35 in rear? Thats what i've been putting and i have alot less vibration on the freeways and highways.
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Old 10-31-2006, 10:03 AM   #10
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I don't think you should deviate more than 4 pounds between front and rear.
maybe the flat spotting of your tires is more pronounced at higher pressures.
which reminds me I'm due for an alignment.
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Old 10-31-2006, 10:25 AM   #11
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I have found that during autocrosses when the front is lower than the rear the car understeers just like everyone has mentioned. When the tires heat up and the pressures increase I take pressure out of the rear to equalize between front and rear. The result is a more neutral/oversteer handling.

I think most people would prefer the neutral/oversteer handling when doing high performance driving which is why I think you liked the 28 psi all around better than the factory specs. IMHO 28 psi is too low...

Either way, for everday driving use the factory specs as understeer is much safer for everyone in all types of conditions. For the occasional twisties in good weather, I would pump them up in the 36+ psi range all around.
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