I,ve always been told that when it comes to tire air pressure to go by the automobile Mfg recommendation (usually on a sticker in the door jamb) and not by the pressure recomended on the tire itself. But hot rods don't have door stickers,so how are you to determine what is the best pressure to run,for best ride and optimum tire wear? For example,My car is a Model A roadster,on a 32 frame with a 390 Cadillac engine,I've never had it weighed,so don't know the weight,but It stands to reason thet the rear is a lot lighter than the front. THEN,I have 750x16 and 600x16 tires (Excelsior radials) and the 750's are 6 ply!!!So I have rear tires that are meant to carry a lot of weight on a rear that is light. And that is the case on a lot of our cars--------so It seems to me that I should use more psi in the front than in the rear--does that make sense?? And I'm wondering just how low of pressure I can run safely in the rear (they are tube type) So has anyone ever figured out a formula for this?
My 32 is similair weight i would think with 394 Olds/hydro and i have 560/15 firestone with 25psi, rears are 890/15 firestone with 26psi, all seems fine.
I run 18 psi in the rear tires and 28 psi in the front tires on my hiboy roadster. Tires are radials thou. It seems to work just fine, been doing it for 27 years now with no problems. My car weights 2,370 lbs. with a full tank of gas. Hope this helps.
i know its no roadster, but my A pickup weighs 2300 pounds. i'm experimenting with my 6 ply rears around 26-28 pounds. My fronts are at 30.
On any car I watch for even tire tread depth wear across the tread over time. Initially I measure the tire pressure when cold and then hot. I like to see a 3-5psi pressure increase. You can also roll through a water puddle onto clean cement and look at the tread pattern to see if it looks even. Best is getting even tread wear over time.
With a radial they seem to have full contact no matter what pressure---with a bias they balloon up with more pressure causing middle of tire wear
think i have been down to 12 on rear for ride 2300 pd car and radials check tires for heat after driving have had them pretty low and no heat and a nice ride otherwise it is a lumber wagon at recomended press
when I had my 28A delivery with 275x75-15 radials. Finally got down to 12lb., had a good ride and no extra wear.
When in question I've always used the method of putting a few chalk lines across the tire then drive the car hard. If the line is rubbed off up onto the sidewalls I increase pressure, if it's still left on the edges of the tread I reduce pressure. Seems to work?
28-35 front, 18-25 rear. I've had a few different tire combinations over the years, and each liked a slightly different combination. LT type tires liked a little lower pressure, P metric tires ride and handle better (are quieter, too) even at a little higher pressure. Handling is substantially better toward the higher end of the pressure range. The different pressures might effect the way the tires wear, but with the load from a roadster, a radial tire will still go a long way before it is worn out.
Gary, I've got 700R15's on the rear of my highboy '32 pickup. They are D rated tires. I run about 25 PSI in them and they ride just fine. I have 165R15's on the front and I run about 28 PSI in them. I hope this helps.
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