Well, the sticker inside the door jam is only accurate if you still have the stock tires on the car. Look at the sidewall of the tire, and the MAX pressure acceptable for that tire will be written on it. I run my tires on the high side, because that's how I like them. It helps improve fuel mileage, and I like the way they handle when they are pumped up firm. Less pressure will improve ride quality.
I had an interesting 1st hand experience that showed me the importance of proper tire pressure. After getting my new suspension, tires and wheels, I was disappointed. The car had more understeer at the limit than stock, it just didn't handle as well. So I checked the tire pressure. 47 psi hot!!! The tire shop forgot to air the tires down after setting the bead with high pressure. I aired them down to 32 psi and it handles like a dream. I don't know the optimum pressure, but 32 psi cold is what I run. I agree with Grey Ghost that higher pressure will reduce rolling resistence, but I think performance suffers.
My Prized Ride: 2008 Challenger SRT8, Brilliant Black
Eibach Pro System Plus - Springs, Dampers, Sways
Vossen VVS-078 Wheels, Staggered, Silver with Stainless Lip
Front: 22" x 9" with 265/35ZR22 Dunlop SP Sport Maxx
Rear: 22" x 10-1/2" with 285/35ZR22 Kumho Ecsta SPT
Too high pressure will cause premature center tread wear. You could also not be running on the full width of the tread as a result. Under-inflation causes the other treads to wear more.
General rule is for high speed operation/handling you can go about 4 PSI (cold inflation) above the recommended pressure above the sticker/placard on the vehicle.
Always check the tire pressure when COLD (not sitting in sun, not driven for 4 hours, etc) best to check after sitting overnight for lowest reading . I've observed PSI readings go up by 5 PSI over the cold reading per TPMS.
The max pressure molded into the sidewall is the MAX inflation pressure for installing/seating the bead on the rim by the tire installer.
Any higher than those posted pressures can cause seperation of plies within the tire's casing - not intended to be driven at those pressures (sometimes in the 50 PSI range) nor supporting the weight of the vehicle with the tires inflated at that high a pressure.
ALSO - check your cold pressure as your ambient temperatures (winter) drop. Every 10* of temperature will drop your PSI readings.
For example, the overnight lows in my area are mid 40s right now...in another month it can drop to low 30s/high 20s or lower if we get unusual weather.
2009 R/T 27J pkg (6 speed MT) ordered 7/17/08, built 10/23/08, home on 11/13/08
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