Correct Tire Pressure...
Thread Starter
Melting Slicks
Joined: Feb 1999
Posts: 2,473
Likes: 10
From: New Paltz, New York USA
Richard, My car is a 78 so the recommended pressure is different than your 81. Here's what I found on yours:
1981 Tire and Wheels
Standard Tire size--P225/70R15
Type--Steel Belted Radial"
Inflation Pressure (cold) front--35 PSI rear---35 PSI
Revolutions per mile--(45 MPH)--760
Standard Wheel--Short spoke spider, steel rim--15x8
Wheel Offset= -0.50"
Optional Tire--Good Year Eagle GT"
Size--P255/60R15
Type-- Steel Belted Radial
Optional Wheel--Cast Aluminum
Rim Size--15x8
Wheel Offset= -0.50"
I don't know if GM made any significant changes to the suspension in those 3 years or if it was mostly fuel ratings being improved by increasing the pressure. If I was you, I would go + or - 10%. Reduce for a smoother ride cruising or increase for stiffer ride if your a hard driver or on the track. As some stated earlier, you can experiment some too within reason. Ultimately you can judge by the tire wear with even being optimal. Too low and you'll wear the shoulders, too high and you'll wear the centers.
Hope I haven't confused you... Jay
1981 Tire and Wheels
Standard Tire size--P225/70R15
Type--Steel Belted Radial"
Inflation Pressure (cold) front--35 PSI rear---35 PSI
Revolutions per mile--(45 MPH)--760
Standard Wheel--Short spoke spider, steel rim--15x8
Wheel Offset= -0.50"
Optional Tire--Good Year Eagle GT"
Size--P255/60R15
Type-- Steel Belted Radial
Optional Wheel--Cast Aluminum
Rim Size--15x8
Wheel Offset= -0.50"
I don't know if GM made any significant changes to the suspension in those 3 years or if it was mostly fuel ratings being improved by increasing the pressure. If I was you, I would go + or - 10%. Reduce for a smoother ride cruising or increase for stiffer ride if your a hard driver or on the track. As some stated earlier, you can experiment some too within reason. Ultimately you can judge by the tire wear with even being optimal. Too low and you'll wear the shoulders, too high and you'll wear the centers.
Hope I haven't confused you... Jay
One more time, thank you. Like I said earlier, the tire installer had the pressure set at 35PSI. To me it seemed a little stiffer that it has been, which is why I posted here. Anyway I am going to set all pressures at 32 and see how it feels. I do not drive the car that much so I am not worried about any kind of wear. Thanks again, have a great day.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Setting radial tire pressures based on vehicle weight (load) is the same mistake that American car companies made initially. A wide radial tire with 20-24 psi would be enough to handle the LOADING. Unfortunately, that amount of pressure won't pump up the tire adequately and the extreme amount of sidewall flexing from such low pressures would cause excessive sidewall heating and early blowouts at highway speeds. Exactly what happened in the mid-70's.
