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Strange tire tread roundness.

98XJ

NAXJA Forum User
Location
Duvall, WA
Hi !
I bought 33x9.5 Big O tires XT. Good tire, however, when I installed tires on 15X7 wheels, I noticed that tread is kinda rounded and edges of tires do not touch pavement at all (even at lower Psi). I've talked to several good people, they said get 15X8, it should take care of the problem. I got smoe 15X8, its slightly better, but edges still do not touch pavement at 30 Psi.
Has anyone had that kinda of problem with tires. Weird enough, I have a 33x9.5 BFG (spare tire) on stock 15x7 wheel and tread is flat when mounted on vehicle.
I don't get it.
TIA for helpful hints!
 
Last edited:
25 Psi. Didnt go lower because very shaky handling on hwy.
 
I had to run my 285's (33x11.50/16x8/D-rated) with about 28psi to finally get it to sit flat. They're rated at 3300 lbs./tire and that's about the weight of my entire Jeep, so I just figured less air pressure was normal since I'm running such a big tire on such a small, light vehicle.
 
That 3300lbs/tire is at whatever max rating is shown on the sidewall as well (50psi, etc) If you ran at that size, expect to get your teeth shaken...my broth....errr...a family friend was ready to sell his truck because of the terrible ride before it was pointed out that the PSI number on the sidewall was not an indication of how full to fill it.

30psi on most tires may still be high for a light vehicle like a Cherokee; the reason the tires seemed to contact better with the 15x8 rims instead of the 15x7s is really just a matter of rim width. As you mount them on a wider rim, the tread portion will do that.
 
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