KingBiscuit2112

I'm 17's and 18's (Goodyear Eagle F1 Asymmetric) on an '89 C4*daily driver).There is a wide range of pressure that is listed for those tires, any suggestions would be appreciated

c4cruiser

Start by using the recommended tire pressure as shown on the driver's door sticker (most likely 35psi both front and rear. From there, you can make minor adjustments to suit ride quality or performance handling.

QCVette

17's and 18's were not the stock '89 sizes.

If they are the stock sizes (wheel widths and tire sizes) from a C5 the OEM recommended pressure was 30 psi.

Like c4cruiser said start with what you think might be best and make adjustments from there. In addition to ride quality and/or handling, you can look for tire wear (or contact patterns). If they are wearing in the middle, the pressure is too high, if they are wearing at the edges, then the pressure is too low. Sometimes the rears can be checked with a little tire spin to see the contact pattern.

When you start with non stock sizes (especially widths of tires and wheels) you may need to make a guess and adjust from there.

Good luck

Christi@n

I run 37 PSI when tyre reach operatig temp

1995 17" fr adn rr

DGXR

37 PSI at operating temperature is about 33 PSI cold.

I run around 32-35 PSI and don't fuss with the pressures unless they are more than a pound difference among all 4, or they get out of the 32-35 PSI range of course. They all keep/lose air at about the same rate so I don't have to air them often... go up to 35, slowly discharge down to 32 over a few months time, then air up again to 35. I do check the pressures monthly.
Mine is a 1995 base with standard suspension and stock wheel/tire sizes (255/45-17 front, 285/40-17 rear). I don't track the car, just normal driving and occasional "spirited" runs.

Christi@n

Hot Rod Roy

The front and rear pressures don't need to be the same, especially if your front and rear tire sizes aren't the same. As you raise the front tire pressures vs. the rears, the car will tend toward oversteer. As you reduce the front tire pressures vs. the rears, it will tend toward understeer.

The staggered tire sizes like you have will make the car tend toward understeer (with equal tire pressures), so you will probably want higher air pressures in the front tires.

I find that my car handles and rides best with 36 front and 32 rear tire pressures. My tire wear is very uniform.

KingBiscuit2112

That sounds like something to try, thanks for the information.

DGXR

This is confusing to me. As I understand it, higher tire pressures make a harder tire and provide less grip, and lower tire pressures make a softer tire and provide more grip. To a point, of course.

Oversteer means the rear end tends to break loose in a turn. Understeer means the front tires tend to plow in a turn and the car doesn't rotate very well.

So higher front pressures mean less front grip, which could produce an understeer condition (plowing). And lower front pressures allow more front grip, which could produce an oversteer condition. I have been wrong countless times before, so please correct me.

I agree that equal tire pressures could produce an understeer condition because the standard setup has narrower front tires, with less grip, all things being equal. I think engineers (and the NHTSA) prefer a tendency toward understeer for vehicles sold to the general public, just safer... umm... I mean less dangerous than oversteer. And less fun.

FASTAZU

17's on all corners I also run 32 rear 35 front. Ran the same pressures with my C5 got over 40k miles out of the tires.

Hot Rod Roy

Now you're catching on!

Try it, you'll like it!

I didn't say this would cause the car to oversteer, I said this is a technique to balance the handling of your car for optimum handling. You probably won't notice any difference unless you enjoy performance driving. If you're just a cruiser, you won't notice any difference. Oversteer or understeer is an extreme handling problem.

Since your butt is so close to the rear axle, you'll likely enjoy a better ride with less air pressure in the rear tires.