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What is the proper Tire pressure for Cooper STT Pro 37x12.5x17?

CWWatkins

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I just did a Mopar Lift on my new 19 JLUR. I put 37x12.5x17 tires on it the dealer put the tire pressure at 38 PSI. What should it be to get best ride and wear?
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Carlton

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I just did a Mopar Lift on my new 19 JLUR. I put 37x12.5x17 tires on it the dealer put the tire pressure at 38 PSI. What should it be to get best ride and wear?
Between 28-32 PSI. I'd start at 32, see how they feel, and go from there.
 

Tritonman

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There is no universal pressure number that yields the best wear vs comfort etc. There are variations in weight of the vehicle along with the tire rating as other examples that impact tire pressure. With that being said, your best bet is to do the good ole chalk test to find out what best works for your situation. Typically your average jeep owner with tires that size usually runs around 28-32 psi.

Chalk test - make sure your tires are cold and have not been driven. Find a flat spot for the test, like your driveway assuming its flat. Make sure the Jeep has its normal weight load that's typically in it daily driving. Draw a heavy thick line of chalk on the tread part of your tires. Now drive one to two rotations of your tire and look at the chalk lines on the tire.

If the outside edges of the chalk on the tires is worn but not the middle part then you dont have enough air.

If the middle part of the tire has less chalk than the outside edges you have too much air.

Try to find the best pressure that yields even "removal" of chalk. This is not a perfect science but it's a very good solid method. Dont forget as the tires wear or if you add more weight like bumpers etc then you need to do the process again.
 

AggieJeepGuy

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I think Tritonman meant if the middle has more chalk on that second part, but I’m running 30-32 on my 37in cooper ST Maxx. Sidewall rating (d/e) can make a big difference. I could drop my 35 cooper pros on my jk down to mid 20s and not get even wear (e rated) but these (d) seem pretty good at that 30ish range. I don’t have bumpers, winch, etc yet to add weight so will see how things change as the weight goes on.
 

Tritonman

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I think Tritonman meant if the middle has more chalk on that second part, but I’m running 30-32 on my 37in cooper ST Maxx. Sidewall rating (d/e) can make a big difference. I could drop my 35 cooper pros on my jk down to mid 20s and not get even wear (e rated) but these (d) seem pretty good at that 30ish range. I don’t have bumpers, winch, etc yet to add weight so will see how things change as the weight goes on.
Yep, you are correct. I was half asleep when i posted :) That will teach me. Thanks for the clarification!
 

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NFRs2000NYC

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38 is too high, you should be in the high 20s, maybe 30-32 if doing a cross country road trip.
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