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I just did the tire chalk test on my JKU and ended up right at 22psi for all tires to get a good wear all the way across the tire. Does that seem too low for normal driving? It rides fine without pulling and it seems to be just a little louder than when tires went on last week but not obnoxious.

I did the test with a full tank of gas and the front doors off. The only added weight that I have is rock sliders that add about 75lbs. Tires are 315/75/16 Duratracs.

Thanks!
 

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Does seem a bit low, especially for a JKU. Are they E rated tires?
 

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Seems Low

Seems low for daily driving. I could be wrong but I run my KM2's at 32 PSI in town. I've been told by others that this is the optimum for DD and I should get about 50K out of them. Mine are E rated.
 

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Forgot to type what I run- 35" GY MTR Kevlars at 24-26 PSI. They are C-rated but have stiff sidewalls. I think 26-28 is where most run these. I can't go over 28- the ride is too rough and there is hardly any sidewall bulge.
 

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Thanks for the replies...I'll redo it and double check to make sure that I colored within lines...I wasn't the best at that when I was younger. It might have carried over into adulthood. :doh:

Yes, they are E rated tires.
 

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I have the same tires, the E rating makes them a bit stiffer. I found the perfect psi at 29, warm. I wouldn't run them that low (22) on street, but the tires can heat up during driving causing a higher psi reading too after driving.

My tires, cold, in the early morning with temps in the high 70's or low 80's will sometimes be 26. Even if I don't drive it at all in the morning, by noon, with temps in the 90's and sunshine on the Jeep, the cold psi will be at 28-29. Driving brings it back up to 30 sometimes.

If you really want to see how the tires are doing, take some latex paint and paint a line about an inch wide across the entire tread. Let it dry, and go for a drive on paved roads or highway. Drive some miles, I prefer doing this when I run errands and work, and I don't check it for at least 15 miles. If there's 1/4 inch on the edge or less when you are done you are good to go if you like the feel of it. A half inch is ok, I think mine are probably closer to a half inch sometimes.
 

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If you have 12.5" wide tires you're NOT going to get full contact. I do not agree with the chalk test whatsoever. those wide tires aren't wide for traction on the street. When the surface starts getting soft, it will come to the tire. Plus you'd probably air down to 14 or so PSI for real wheeling anyway.

For a daily driver, I'd start at about 36 PSI, and lower the tire pressure a little at a time and judge what happens to ride comfort and MPG. You want more air for more MPG, less air for ride quality..... have to find where you're comfortable with it. I'm at 28psi with duratrac 33x12.5s on 8 inch rims.

If you cant stand driving with them over 28 PSI I'd probably suggest 26. If you have to use 22psi for it to be a reasonable ride, then go ahead and do it. Also, big offroad tires *do* have a negative ride quality impact, and we do have to accept that to a certain extent. The size and shape of open space between treads, number of plies in the tire, size of the sidewall, weight of the tire all have an impact on this.
 
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