Thread: understeer
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Old 06-17-2009, 11:08 AM   #5
70Sixter
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Join Date: Jun 2005
Location: Surf City, NC
Posts: 1,079
Understeer ("push" in NASCAReez) is corrected by balancing the car. The Boxster 29Front- 36 Rear contributes to the front bias which keeps the rears planted longer than the fronts and staves off oversteer. Like my old 911 had in spades.

In simplest terms at the limit an understeering car will go off the track nose first, and one that oversteers ("loose" in NASCAR) will go off tail first

To correct for understeer you want to INCREASE front tire pressure and/or decrease rear tire pressure. I run 30-35 on the street. And believe 32-35 is safe in an experienced drivers hands for 8-9/10ths canyon carving.

Some say you should go more negative in rear camber rather than adjust pressure down, but I think for a street car that is sometimes tracked that the tire wear would be intolerable for most.

James, I'd say your 25psi front pressure is not safe and is probably below the manufacturers minimum recommended pressure. You could drive the tire off the rim. I did not check Sumitomo's recs, but I'd go to 30F-35R immediately and work from there.

Your other specs look basically neutral to f-r balance.

Tire temp is a very good indicator of which tire or part of the tire is scrubbing the hardest. Hot fronts indicate understeer. Pyrometers are useful for measuring, but touch and chalking the sidewalls are good enough for casual tracking.
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04 Boxster S - Basalt/Savanna, 6sp, Carrera lites, hardtop
70 914-6 - Black over tan, original/stock
PCA since 1970
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