Tire pressure??
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From: Blythewood S.C.
St. Jude Donor '14
Tire pressure??
What kind of tire pressure is good for the C3's. The door panel on my '78 L82 4spd indicates to run 28 lbs. front and 32 lbs. rear for max load and 20 front and 26 rear for reduced load. These seem a little low to me. That's for a P255/60R 15 inch tire. I have Goodyear GTII's on mine and get some vibration that is driving me crazy. Anyone else have these humming/vibrations? Mine starts at 65 to 70 mph and just gets worse the faster you go. 
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30 to 32 cold with radial tires 
Drifting
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The C3 tires were almost oversized. If you look at the load rating of the tire, compared to the actual weight sitting on each tire when the car is parked, you will see what I am talking about. The 225-70R15 tire is rated at 1753 lbs at 35 psig. Lower tire pressures reduce the load rating. So if your C3 weighs 3500 lbs, each tire carries only about about 875 lbs. So if you run those lower tire pressures, they will give a nice soft ride and not be overloaded, with gentle driving. When you corner, the outside tires are carrying more load than that. Braking puts extra loads on the the front tires. Higher air pressures can handle those loads better, without excessive distortion of the tire carcass.
Having said that, I run about 30 psi all around, on 235-60R15's. If you have the 255-60R15's, I'd run 28 psi. Any more than that seems to ride a bit harsh, and any less feels sloppy. Anything in that range would be fine.
Salt to taste.
As far as your vibration is concerned, the tires could be flat spotted or out of balance. Sometimes, if an old tire hasn't moved in a while, it will temporarily have a flat spot, which often goes away after some miles of highway driving. Could be time for a bit of a road trip.
Having said that, I run about 30 psi all around, on 235-60R15's. If you have the 255-60R15's, I'd run 28 psi. Any more than that seems to ride a bit harsh, and any less feels sloppy. Anything in that range would be fine.
Salt to taste.
As far as your vibration is concerned, the tires could be flat spotted or out of balance. Sometimes, if an old tire hasn't moved in a while, it will temporarily have a flat spot, which often goes away after some miles of highway driving. Could be time for a bit of a road trip.
Last edited by gcusmano74; Mar 25, 2012 at 02:05 PM.
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From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
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Its been well covered but the info on your door and manual is for bias ply tires. On your modern radials I use 30-32 just like most of the guys above !
P.s. Your vibration is much more likely to be a balance issue especially if it changes w/ speed!
P.s. Your vibration is much more likely to be a balance issue especially if it changes w/ speed!
Last edited by BPHORSEGUY; Mar 25, 2012 at 11:56 AM.
