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TRcheologist
09-24-2008, 04:25 PM
I have a question regarding tire pressures with tubed tires. I'm new to wire wheels and tubes, having run tubeless radial tires on steel wheels for many years. I've always run between 40-42 psi on the tubeless tires. Can I run comparable pressures on tubed tires, or are lower pressures recommended?

Thanks

TR3driver
09-24-2008, 04:33 PM
You shouldn't need to change pressures because of the tubes; but 40-42 (cold) seems kind of high to me. I certainly would not exceed the pressure given on the sidewall of the tires.

TRcheologist
09-24-2008, 05:33 PM
Thanks. The sidewalls indicate a 44 psi max. I didn't know if tubes could support the same kind of pressure.

swift6
09-24-2008, 05:54 PM
MAX PSI sidewall ratings should only be used as a "do not exceed" pressure. Tires are designed to be used on multiple vehicles that would all have varied recommended tire pressures. Use your owners manual to determine the correct tire pressure for your car, not the sidewall (just don't exceed the sidewall rating and chances are you won't be close to it anyway). Most modern radials like a few more psi than what your manual would typically call for though. But only a couple of psi.

On your TR3A, the manual calls for 22lbs front and 24 lbs rear. Many owners find that with modern radials something more like 30psi front and rear gives a good compromise between wear, handling, comfort and mileage. If you have been running 42 psi, you have probably been getting good mileage with a rough ride and "loose" handling.

I have never heard of wire wheeled tires needing more psi than steel wheeled tires. If so... news to me (wouldn't be the first, won't be the last I'm sure).

Long post short... the psi rating on the sidewall has nothing to do with what pressure your should be using on your car. Only a pressure you should not exceed.

TR3driver
09-24-2008, 07:02 PM
On your TR3A, the manual calls for 22lbs front and 24 lbs rear.Those are the bias-ply numbers. Radials (ie Michelin X) are given as 24 front and 28 rear, with some versions noting to increase pressures by 5 psi "if the car is driven consistently hard and fast".

I found that somewhere around 32-34 seemed to work best for me ... but then neither the car nor the tires were exactly stock.

Nothing wrong with cautiously experimenting with higher pressures (within the sidewall spec); but keep in mind that the car's handling may become unpredictable in emergency situations or near the limits of adhesion.

swift6
09-24-2008, 11:41 PM
On your TR3A, the manual calls for 22lbs front and 24 lbs rear.Those are the bias-ply numbers.

I actually meant to mention that those were for bias-ply and that modern radials work better with more psi. Though 42psi is still pretty high for street driving on a TR3A. Good for autocrossing though. :smile:

NickMorgan
09-25-2008, 02:33 PM
I have been playing around with the tyre pressures on my TR and have found that 30 all round seems to work best. Certainly when I replaced my tyres recently the old tyres showed nice even wear, which points to correct pressures.