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Old 06-06-2015, 06:58 AM   #1
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Upgraded to 17's

I just upgraded my 2004 base Box to Tire Rack Cup 4 17 inch wheels and a set of Potenza RE-11's with 3 DE days on them. The gentleman i bought them from said he used 30 PSI in the front and 36 PSI in the rear. My question is: Should I run 34/38 or some similar ration for auto-X events.

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Old 06-06-2015, 07:47 AM   #2
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Quote:
Originally Posted by Blackcloud View Post
I just upgraded my 2004 base Box to Tire Rack Cup 4 17 inch wheels and a set of Potenza RE-11's with 3 DE days on them. The gentleman i bought them from said he used 30 PSI in the front and 36 PSI in the rear. My question is: Should I run 34/38 or some similar ration for auto-X events.
When I ran 17's for AX I started with 32 psi front (from normal 29psi for street) and 38 psi rear (from 36 street) and checked the sidewall roll indicators after the tires got hot. Get and carry a good and accurate tire pressure gauge. If the indicators showed scrub to the bottom of the diamond the tire was rolling over too much and needed more pressure and if it's not scrubbing to the top of the indicator then air need to be let out. Ideally you want to see scrub right to the top of the roll indicator. Typically, after getting hot, the tires would need to be bled as pressure went to 36 psi front and 40 psi rear. I believe your Bridgestones have a very stiff sidewall so your pressure will vary and starting where you indicated is probably a good starting point.
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Old 06-06-2015, 09:07 AM   #3
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Thanks. I have a good pressure gauge. Sounds like good advice. Thanks for the feedback!
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Old 06-07-2015, 06:55 AM   #4
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Your tire pressures will depend somewhat on the surface (track/parking lot) conditions, ambient temp, driving style, changing understeer/oversteer, etc. You probably will need to experiment a bit to find the "right" pressure.

get a good racing tire pressure gauge, best one of the oil filled ones that adapt for ambient temp. You can find them on amazon and ebay for around $40.

I find that my tires (Hancook Ventus V12 Evo2) when driven hard at AX or the track get slippery when very hot and I run much lower pressure than I do for normal spirited driving.

Different tires will act differently. Tire pressure for performance driving is a mix or art and science
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Old 06-08-2015, 08:38 AM   #5
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Quote:
Originally Posted by Blackcloud View Post
I just upgraded my 2004 base Box to Tire Rack Cup 4 17 inch wheels and a set of Potenza RE-11's with 3 DE days on them. The gentleman i bought them from said he used 30 PSI in the front and 36 PSI in the rear. My question is: Should I run 34/38 or some similar ration for auto-X events.
Short answer - HELL NO!

That is WAY too much pressure for an AX, but as others have pointed out, you will need to experiment. I run as low as 22/24 lbs up to 26/28 on my Toyo R888's. Keep dropping 2 lbs until you get too much tire roll. Get a Harbor Freight Air tank so you can put more air in if you go too low :-)

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