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Old 08-22-2012, 04:31 AM   #1
GiantSchnauzer's Avatar
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psi question , coopers stt

33x12.50x17 cooper stt load range D max press 50psi on 17x9 rims,

I have had no time to do the chalk test, from the dealer they where filled up to 39is and I aired them down to 33 but appears from the dust on the tires left by the street they need to perhaps go down to 31ish . Is this an ok psi area until i test with chalk?, not sure because its my first "d" range tire. Rides better just sounds a shitload under 50 if i air down any more.
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Old 08-22-2012, 06:13 AM   #2
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On my 2 door JK I normally run my D rated Cooper Discoverer S/T, 285/75R16 (33x11.5), at 28 psi on the street. I am on my second set after getting 65,000 miles out of the first set and have 20,000 miles on this set and get pretty even tire wear at this pressure.

If I am towing my camper or have it loaded heavily for a family road trip I'll air up to 32 psi and off-road I air them down to 10-15 psi depending on the terrain.

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Old 08-22-2012, 07:50 AM   #3
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Thanx jeeping, ill try 30psi and see how it looks. Just wanted to make sure i am not lowering the pressure too much in relation to the max psi.
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Old 08-22-2012, 04:51 PM   #4
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If you can find a load vs. inflation table for them it will tell you exactly what to run. I've run as low as 25 for that size. You'll find that most run them between 27 and 30 psi. Don't worry about the number on the sidewall. That's the Max. Look at the sticker in the door jam. That tire should be the same or a couple of pounds less than factory spec but no Morse than what Jeep recommends unless its packed full and loaded heavy.
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