Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Tire pressure

My car came with polyester tread tires so the specs (tire pressure)on the car do not match the radials she has now. What is the correct pressure for a P225/75R15 radial?

And case you care her name is Blanche Du Bois and she a 79 Lincoln Continental.

The correct pressure goes with the car, not the tire. On one of your door pillars there is probably a label of sorts. It will tell you what the pressure is for front & rear (they could be different). Follow that (so long as it doesn’t exceed the cold pressure max on the tire’s sidewall).

In general Cig is right, but a '79 might have come with bias ply tires rather than radials…is that what you meant? Radials do use different pressures, and the bias ply pressure recommended may not be correct for the radials.

If it were me I’d start with 32 psi in the front and 30 in the rear, adjust it until it feels balanced front-to-rear (no excessive understeer or oversteer), and then watch the wear patterns and adjust as necessary.

If the car did originally come with radials, use the recommended pressures on the door jam and owner’s manual.

Ahhhh…never crossed mind. I’m just a little bit of a thing and barely remember anything about when bias ply tires were common. I did own a '64 Ford pickup for quite a while and spent only a little bit of time (b/c I didn’t know any better) w/ radials on the back & bias on the front. That was an adventure - so to speak.

But its always a good day when I learn something new (though I guess that OP will have to come back to clarify before it really sinks in). Thanks MB

The door jamb sticker on my 93 Caprice (similar size and weight) recommends 30 psi front and rear. I keep the pressure at 32 psi as I prefer a crisper steering response. Start with the tire pressure between 30-32 and adjust as required. I wouldn’t go below 30 psi though.

Ed B.

I only thought of it because I go back that far…and beyond.

You need to go back t the 60’s for bias ply original equipment. A '79 used radials.

My '72 Vega came with bias ply.

You may be right about the '79 Linc, however. I acknowledged that I might be incorrect on that in my original reply.

well my copy of the 1979 tire guide by Bennett Garfield publications gives the following
OE size 225R15 30 psi front and rear.
optional tire size LR78-15 30 psi front and rear.
being that these were not P metric tires that actually require a higher psi i would go 32 psi front and rear

just a note i have tire guides going back to 72

Well done.

According tire Tire Guides Oldertimer’s Tire Guide, a 1979 Lincoln Continental originally came with 225R15’s inflated to 30 psi. Unfortunately, these are 82 aspect ratio and the current tires are 75 aspect ratio - so the inflation pressures would be different.

  • and digging up the old tire load tables, the equivalent load carrying capacity occurs at 35 psi.

The local tire store recommended 35psi all around but the post for 32 front 30 back is closer after some more investigation elsewhere it seems 32 is best all around but others say 35 front and 32 rear. Close enough for me. PS there was nothing on the door as it is worn away.

Thanks that is good info after going back this is also what I found. You are correct.