07' Unlimted JK Rubicon running 37's for some time no w/o issue (at least 4500miles).

As of lately (last 400 miles0 the inside and outside tread is starting to wear on all 4 tires.

Questions is the only change since the wear has started was running 5 lbs of extra psi in each tire (now at 40psi each) and added 1.5" spidertrax spacers.

Want opinions..... is it the added psi or the addition of Spideertrax spacers..... or both?

 

Wearing on the outsides generally means the air pressure is too low, or the rim is too wide. Over in flation, or a rim that is too narrow will wear the center of the tire faster than the outside. What rims are you running them on?

 

Dont think it's the rims, been running 17 x 9 Pro Comps for quite a while. Wear only started in the last 400 miles after I raised the psi and added the wheel spacers at the same time

Only thing that has been changed was higher psi and added 1.5" spacers.

Just figured i'd ask rather then taking the spacers off and or lowering the psi. Obviously if I did either I wouldnt have an immediate answer. Hoping someone can chime in with a definate answer.

 

Well, you can limit out the air pressure eas enough. Find some nice smooth concrete (blacktop generally is not flat enough and draw a chock line on the ground in front of your tire, or draw on the tire itself (one may work better than the other depending ont he surface of the concrete). Then slowly roll over it. Now look at the line and see how much of it was or was not rubbed away. My guess is the outside will be touched, the middle will not be. Which almost always means low air pressure. So anyway, after testing this, vary the air pressure, try going up more, or down more, etc.

 

It does seem like an issue caused by too little pressure, but if you're running 40psi, you would most likely be having the opposite problem as that seems like too much pressure. Most people around here seem to be running high 20's to low 30's for street driving. Personally, I run 32psi...