The tire pressures listed on the placard are what the car was designed for. My '74 also says 20 psi, and that's what I run them at, unless I'm on the road, with a load. I will then pump them up to 28psi...no more. More air makes the car twitchy in the twisties, and it rides much rougher.....I don't like that.
Putting too much more air in them than the factory recommends will alter the handling, and may make the vehicle unstable at certain speeds, if you're running thru the mountains, or on a track.
The listings on the tire sidewalls are normally for the
maximum pressure recommended at maximum rated load of the vehicle.
I don't think 26psi is too low, Stephane, especially on a big block car.
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Joel Adams
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