What tire pressures do I use frnt and rear

[[email protected]]

I'm running 235 75 R15 tires on my 1955 F-100 with a 5.0L FORD V8 and c6 trans and 9" REAR. What should my tire pressures be?

[dmsfrr]

What pressure are you using now? Is there a tire wear or another problem you're trying to fix?
Given the assumed lighter rear weight, a few less psi in the rear tires than the front would be normal.

30 or 32 to 35 psi might be a good place to start unless you're getting too much wear in the center of the tire.
See the example wear patterns at this link...
https://www.freeasestudyguides.com/t...-patterns.html

In general, under inflation is not as safe as inflation up to the max pressure shown on the sidewall.
Low pressure creates additional sidewall flex and can lead to tire overheating and casing failure.

Are the tires nearly new or more than 6 to 8 years old? Old tires are more subject to blowouts, especially at hiway speeds. Look for the 4 digit date code on the sidewall. If it's a 3 digit code the tires were made before 2000.
.

[paul2748]

On a radial, I generally use 32 lbs.

[Daves55Sedan]

Once I finally switched to radial tires on my '55 Ford, I had to look on the tire to see what the maximum tire pressure is on the tire sidewall. I was surprised to see 44 psi, so I usually to to keep them filled to around 41psi.
Look on the tire sidewall and run them a few pounds lower than their recommendation (especially during summer months)

[dmsfrr]

Originally Posted by Daves55Sedan

... I was surprised to see 44 psi, so I usually to to keep them filled to around 41psi.
Look on the tire sidewall and run them a few pounds lower than their recommendation (especially during summer months)

Yes, I'd forgotten about some newer radial tires as they've changed in the last several years. The pressure ratings have increased in the quest for greater fuel efficiency.
The tires on a now gone daily driver showed a max pressure rating of 44 psi and anything less on that particular car wore down the outside edges very quickly. At 44 psi they wore evenly for more miles than they were advertised for so I accepted it.
My more recent DD's aren't quite so picky, they are fine with a few less psi than the max.
It seems that inflating the tires between the max pressure and maybe 10% lower works well.
.

[Daves55Sedan]

Sponsored Links (Register now to hide all advertisements)

I am using P205-75R15's on the front (35psi max), and P215-75R15's on the rear (44psi max).
Why the difference?
The 205's are slightly narrower, which allows extra space between the inner tire sidewall and the top portion of the upper ball joint.
The 215's are wider than the 205's (a little bit), but the outside diameter is within a fraction of an inch of the OEM 670X15 bias ply tires.
I would have preferred something closer to the OEM 710x15 tires for the rear, but the P215's are as close as you can get on a radial.
The set of four costed about $60 per tire back then (about 12 years ago), and back then, no one was offering OEM spec radials. But a couple years ago, they started making bias look radials in many original sizes.
I am running a pair of American Classic bias look 710x15's on the back of my '55 Courier sedan delivery wagon, wide whites, of course, to match the crappy Coker classics I have on the front.
The bias look radials are EXTREMELY expensive, though.

[Vern Appleton]

That's what I love about radial tires, they are ever-changing, in a positive way. The tire pressure increase to make way for fuel-efficiency is a very ingenious way to save us, car owners, a lot of money. Even the tires I buy off 4WheelOnline has the same amount of high-quality and ingenuity you can expect from some of today's top tire brands.

[Lanny]

The tire companies know how to rate their tires for Max PSI.

As Dave says in post #4, see what Max PSI the tire is rated for, and run
a few #'s under that in the front, and a couple less than that in the rear.

A lot of the newer radials have a Max psi of 44, but many of the newer
radials Now have a Max psi of 51, so DON'T go running 35psi in
them, or you will shorten the tire life by a lot.



.

[[email protected]]

My truck feels like it's running on solid rubber.

[paul2748]

I've been following this, and in my experience anything over 35 pounds make it ride like steam roller. In addition, tires must have a certain amount of cushion so over inflation ( 40 lbs or more) may bust up a tire .

[5851a]

Had no idea the pressure had been upped so far on newer tires. I know on my truck if I have no load the recommended pressure make it a bone shaker. I don't know if the door labels have you set it to max payload or what. When I had earlier Bronco there was a test with chalk across the tread, you would chalk then drive across something like a parking lot in a straight line then check the chalk to see if you where getting full and even treadwear. Is there anything like that for passenger cars with newer tires?

[Lanny]

Here is an article about under inflated tires.
===========================

Driving on under-inflated tires is dangerous. According to the National
Highway Traffic Safety Administration, almost 1/3 of passenger cars, light
trucks and SUVs are being driven with at least one under-inflated tire.

Under-inflation is one of the leading causes of tire failure. If tire pressure is
too low, too much of the tire’s surface area touches the road, which
increases friction. Increased friction can cause the tires to overheat,
which can lead to premature wear, tread separation and blowouts.



.