In general, fill the tires to whatever pressure is specified in the driver's door jamb sticker, even if you change wheel/tire size. The suspension system is calibrated to the tire pressure specified. You may get a little better ride by increasing by 1 or 2 PSI, but any more and your ride will probably get worse. This is what I was taught, and it proved true when I switched up to 215/45-R17's. Also check to see you're not driving summer tires in the cold. The rubber gets very hard in cold weather, making the suspension worse.bmw323!!! said:i have that car 3 or 4 months and i took her for a check and it came out just fine with good suspension, but i don't think it's not the original, maybe it's the tire pressure??
i filled the tires 30 psi, and the size is 205/60/15
i have a set of 17/235/45, and i'm going to put them today, how much psi it should be???
I think we're both in agreement, but I guess I'm being a little conservative. But wider, lower profile tires don't necessarily need higher pressures. Volume and pressure are two different things. If you took the same amount of air it takes to get to 30psi on the 15" wheel and put it in the 17", the pressure would probably be much lower. The larger tire would require more air, but not necessarily more density. It also depends on the individual tire's compound and construction. That's why you'll be hard pressed to find a general consensus on tire pressure, your best bet would be to consult the tire's manufacter. What I see is people jacking up the psi to 40 or 45 and even higher, which is definitely not good. That just makes the wheel bounce around like a basketball, very hard for the coils and shocks/struts to control, and you're more susceptible to damage from potholes. I'd say start with the pressures listed on the door, then experiment by going up or down by 1 or 2psi at a time, see how it feels.motor_werke said:I disagree about using the same pressures listed on the door when changing wheel size. I went to 17" wheels from a 98 M3 on my 325. I use the M3 pressures on the low end (not max capacity). When I was using my OE 15", I used the recommended pressure for max capacity to get slightly better gas mileage. The 17's would be awfully soft at low 30's in the rear. With a much wider, lower profile tire, one would think you might need the slightly higher pressures. The pressures are only a few PSI higher from the 15" to the 17". Granted, tirerack or other sites might have more info when going to larger wheels.