I run 30 psi.
Tire pressure
Thread Starter
Pro
Joined: Nov 2017
Posts: 570
Likes: 43
From: North Carolina
Tire pressure
The car: 77 L-48 automatic. The tires: Cooper Cobra 225/70/15. the question is tire pressures. owner's manual says 26 rear and 20 front. i know the owner's manual is over 40 years old. the tire pressures at least on the front seem low. Suggestions? thanks in advance.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Radial tires were new to the USA in that era, and the know-it-all US engineers decided to set tire pressure based on vehicle weight/loading, rather than for what the tire needed. As a result there were many new tires which blew out at highway speeds from excessive sidewall flex (heating) and lots of lawsuits for the tire makers and vehicle builders.
Those owner's manuals were WRONG. Radial tires need to be aired up to around 30psi to be stable and 'healthy'. Some like a little bit less; some like a little more. But less than 28psi is not recommended for a 15" radial tire.
Those owner's manuals were WRONG. Radial tires need to be aired up to around 30psi to be stable and 'healthy'. Some like a little bit less; some like a little more. But less than 28psi is not recommended for a 15" radial tire.
Burning Brakes
Joined: Mar 2013
Posts: 750
Likes: 180
From: Springfield Missouri
My suggestion is to find a level spot, preferably concrete, pour a bit of water down to drive through. Drive through slowly and examine the patch the tire(s) leaves. When it's consistent all across the tread you have the right amount of air in the tire. I prefer to do the front and then the rear.
Drifting
Joined: Dec 2017
Posts: 1,664
Likes: 417
From: Central Texas
30-32 is fine. Your car did not come with Coopers, so the manual info is worthless. Check Cooper website for more info...
http://us.coopertire.com/safety/safe...inflation.aspx
http://us.coopertire.com/safety/safe...inflation.aspx
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Whatever inflation pressure you decide upon, monitor the tread wear pattern. If tread is wearing more in the middle, reduce tire pressure. If wear is equal on outside edges, increase tire pressure. Also assuming the car is properly aligned for this to be beneficial.
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Racer
Joined: Oct 2001
Posts: 474
Likes: 64
From: Portage La Prairie Manitoba
The car: 77 L-48 automatic. The tires: Cooper Cobra 225/70/15. the question is tire pressures. owner's manual says 26 rear and 20 front. i know the owner's manual is over 40 years old. the tire pressures at least on the front seem low. Suggestions? thanks in advance.
Often the tire manufacturer is blamed or a lot of people say old tire.
Proper inflation for that size between 28 and 32 lbs.