Tire Pressure
Thread Starter
Advanced
Joined: Feb 2015
Posts: 76
Likes: 10
From: NEW ORLEANS Louisiana
Tire Pressure
Afternoon everyone.
Have taken possession of a 73 with 240/60r15 on Steel Tally wheels.
The door states 20 psi front and rear.
I believe that to be incorrect as the vehicle originally had Bias tires.
Running 30 all around right now and vehicle sits and rides very nice.
Curious, what others are running?
Have taken possession of a 73 with 240/60r15 on Steel Tally wheels.
The door states 20 psi front and rear.
I believe that to be incorrect as the vehicle originally had Bias tires.
Running 30 all around right now and vehicle sits and rides very nice.
Curious, what others are running?
Burning Brakes
Joined: Nov 2014
Posts: 946
Likes: 211
From: Foothills of the Adirondacks.
Afternoon everyone.
Have taken possession of a 73 with 240/60r15 on Steel Tally wheels.
The door states 20 psi front and rear.
I believe that to be incorrect as the vehicle originally had Bias tires.
Running 30 all around right now and vehicle sits and rides very nice.
Curious, what others are running?
Have taken possession of a 73 with 240/60r15 on Steel Tally wheels.
The door states 20 psi front and rear.
I believe that to be incorrect as the vehicle originally had Bias tires.
Running 30 all around right now and vehicle sits and rides very nice.
Curious, what others are running?
If you have modern performance tires, which you don't if you are running 15" wheel, and you want better handling; get more pressure. 40-45 psi
If you want a plush ride, put less pressure. 25-30 psi
Or anything in between that will suit you.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The first few years of radial tire use in America were 'odd'. Most manufacturers set tire pressures way too low for the tire designs. They were calculating tire pressure values based on tire footprint and vehicle weight, rather than what the tire itself required.
Many early blowouts and tire failures resulted, but eventually the US finally caught on to proper inflation for radial tires. But, the inflation stickers that were installed at that time still specify the WRONG inflation values.
30 psi is appropriate for radial tires on your car. You can run up to 35 if you like a stiffer ride, but the tires work better (under normal circumstances) at 30 psi. Anything from 28-35 psi will work.
If you put 40 psi in your radials, then take it out on the highway for a long trip, tire pressures can increase to beyond rated running pressures as they heat up. Just not a good idea.
If you have low-aspect ratio tires (40 or 45 series), you need to inflate per what those tires need.
Many early blowouts and tire failures resulted, but eventually the US finally caught on to proper inflation for radial tires. But, the inflation stickers that were installed at that time still specify the WRONG inflation values.
30 psi is appropriate for radial tires on your car. You can run up to 35 if you like a stiffer ride, but the tires work better (under normal circumstances) at 30 psi. Anything from 28-35 psi will work.
If you put 40 psi in your radials, then take it out on the highway for a long trip, tire pressures can increase to beyond rated running pressures as they heat up. Just not a good idea.
If you have low-aspect ratio tires (40 or 45 series), you need to inflate per what those tires need.
Le Mans Master
Joined: Oct 2007
Posts: 7,445
Likes: 970
From: Tennessee/Rhode Island
The first few years of radial tire use in America were 'odd'. Most manufacturers set tire pressures way too low for the tire designs. They were calculating tire pressure values based on tire footprint and vehicle weight, rather than what the tire itself required.
Many early blowouts and tire failures resulted, but eventually the US finally caught on to proper inflation for radial tires. But, the inflation stickers that were installed at that time still specify the WRONG inflation values.
30 psi is appropriate for radial tires on your car. You can run up to 35 if you like a stiffer ride, but the tires work better (under normal circumstances) at 30 psi. Anything from 28-35 psi will work.
If you put 40 psi in your radials, then take it out on the highway for a long trip, tire pressures can increase to beyond rated running pressures as they heat up. Just not a good idea.
If you have low-aspect ratio tires (40 or 45 series), you need to inflate per what those tires need.
Many early blowouts and tire failures resulted, but eventually the US finally caught on to proper inflation for radial tires. But, the inflation stickers that were installed at that time still specify the WRONG inflation values.
30 psi is appropriate for radial tires on your car. You can run up to 35 if you like a stiffer ride, but the tires work better (under normal circumstances) at 30 psi. Anything from 28-35 psi will work.
If you put 40 psi in your radials, then take it out on the highway for a long trip, tire pressures can increase to beyond rated running pressures as they heat up. Just not a good idea.
If you have low-aspect ratio tires (40 or 45 series), you need to inflate per what those tires need.
The only caveat is make sure that you check the tire sidewall for maximum pressure for the tire…often that number on a S/T (112/118 MPH, max speed) rated tire (which almost all 15 inch tires for a C3 in the correct sizes for our cars are) is 35 PSI which means that on hot days, the highest pressure you can safely run is about 32-33 cold PSI…
V/Z rated tires (above 149+/168/186 MPH) are generally rated at maximum PSI of 44-52 PSI…All my cars including the 78 L-82 have Z rated tires..I run 40 PSI and the funny thing is the 78 rides MUCH better with the modern rubber (at 40 PSI) than my old 255/60/15 S rated BFG Radial TA's @ 30 PSI by far….
Last edited by jb78L-82; Apr 7, 2015 at 01:02 PM.
Thread Starter
Advanced
Joined: Feb 2015
Posts: 76
Likes: 10
From: NEW ORLEANS Louisiana
All very good info.
Thanks for the insight.
i drove around again in the evening and i believe 30 psi is really perfect.
car handles and grips well, and the ride is actually nice and smooth.
Thanks for the insight.
i drove around again in the evening and i believe 30 psi is really perfect.
car handles and grips well, and the ride is actually nice and smooth.
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Joined: Oct 2000
Posts: 12,652
Likes: 3,110
From: Shamong, NJ
As others had said, GM seemed to think that it was necessary run very low air pressures, when they first started using radials. 20-26 psi was what GM normally recommended, for radial equipped cars in the 70's.
Part of their thinking with the lower pressures, was to improve the car's ride. Besides the switch to radials, the aluminum body mounts used in earlier years, were replaced with rubber body mount cushions in 73. This was also done to help improve the Corvette's ride.