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Tire pressure with larger wheels
Just installed larger 17" wheels with tires 255/40 and 205/50. For street use, should I keep the tire pressure the same as Porsche recommends for the 16" wheels (29F, 36R)? I was wondering if the smaller sidewalls might mean that pressure should be higher to avoid damaging the rims.
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John C 1988 911 Carrera coupe 2002 BMW 530 |
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05-27-2004, 12:02 PM
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For some reason, for some of these larger ( 17", 18") wheels..Porsche advise some ridiculously high pressures...like 44 psi cold.
Track experience from others tells me the standard 30-32 front....34 rear... ( cold )...works well. After some hard use, these increase by 6-7 psi. Apparantly gives good wear pattern across the carcass too. ---Wil
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Wil Ferch 85 Carrera ( gone, but not forgotten ) |
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05-28-2004, 06:18 AM
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The standard for Carreras with 16" wheels is 29 and 36. For what 911s is the stndard 30-32 and 34?
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John C 1988 911 Carrera coupe 2002 BMW 530 |
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05-28-2004, 07:44 AM
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Again..."standard" according to Porsche is indeed 29/36.
I'm speaking of the common "track" or DE standard recommended by a number of track junkies. The 44 psi is especially bad if you're simply driving on the street. It seems to be more of a legal thing ( maybe) in not allowing tires coming off rims at Euro speeds ( Porsche's motives need to be looked at)...so the "track common" recommendation of about 32 fr / 34 rr works well ...even for these 17" and 18" applications...IMHO..... ---Wil
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Wil Ferch 85 Carrera ( gone, but not forgotten ) |
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05-28-2004, 09:06 AM
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Posted question at Audiworld wheel & tire forum and here is an answer I got from Tirerack:
Load capacity at a given PSI is actually the same or even greater on 255/40R17 versus 225/50R16, so no extra PSI is needed. Same story on the front tires. You may use higher psi if you'd like, but watch for more rapid wear on the center ribs of the tread. Gary Tire and Wheel Forum Moderator The Tire Rack, Sales Rep 1-877-522-8473 ext 386
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John C 1988 911 Carrera coupe 2002 BMW 530 |
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05-28-2004, 10:42 AM
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It's strange, but I am getting less inner wear with higher pressures on my 9" Fuchs rears with 245/45s
 I heard some time ago, about higher pressures allow the carcass to flex less on the inside when at speed... maybe I'm just going too fast?!?!?? Average 75 - 80 on freeways. It's a daily driver.
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Nick '85 Carrera |
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05-28-2004, 11:05 AM
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On my daily driver I use to run 44psi Rear per factory specs with my 245/45/16 and after 10K had 2-3/32 more wear in the center while running 0 camber on my turbo. Currently I'm running 34psi on my 315/30/17 with 1 degree neg. per Tyson's suggestion and things are looking good after 4K, surprisingly
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05-28-2004, 11:29 AM
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Tends to reinforce what I'm sayin' .....
--Wil
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Wil Ferch 85 Carrera ( gone, but not forgotten ) |
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05-28-2004, 12:07 PM
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Porsche
