2 years ago i purchased 4 new tires for the first time after owning it for six years.
Last year I had to buy 2 more because the fronts wore out pretty quickly.
I will probably have to do it again this year.
I do know they weighted the wheels for balancing.

What are some common causes? I would ask the mechanic I use but I'm finding more and more that they're fixing my car with used parts that don't work properly. Sadly I'm not very DIY when it comes to mechanics, so I'd like to know what I'm talking about when I roll up to a new shop.

01 Cherokee Sport running with all stock parts.

Also can anyone explain to me how to fix the rear windshield wiper. The nozzle broke off (don't know how) and the hose seems to still be intact.

 

The common causes of tire wear are over or under inflation, wheel alignment out of spec, improper tire rotation, or worn/damaged suspension components. It could be one of these, a combination of these, or all of these. Also know that front tires wear faster than rears anyways, which is why proper rotation is needed. Any mechanic that is replacing worn components with used ones, you need to run far, far away from, and as quickly as possible...

For your nozzle on the back, you can either replace it with one from the salvage yard, pick up a new one, or go to your local hobby/RC shop, and pick up a threaded fuel hose fitting, like for a gas powered plane...tap where the old fitting broke off, put the threaded fitting in, and attach the hose. Only costs a few dollars.

 

This. Alignment, regular checks of the pressure, and regular rotation is very important.

 

You may want to start learning more about how to fix your vehicles. Otherwise you're just a sucker that will pay too much for too little.

 

Search the forums on setting your alignment yourself. Toe in is the only adjustment that needs to be done. Bad ball joints will affect alignment, you can check that for free. I lift front wheels off ground and spin tire and spray paint white paint in middle of tire. While still up and wet paint I hold a nail up to paint while spinning tire. This gives you a perfect mark to take measurements from front and back of tire to check toe in. I burned through a set of tires with a bad toe in alignment too, it tracked straight but wore them out pretty quick.

I agree with Bustedback, A jeep will break your bank account quick if you go to mechanic all the time. Get a repair manual at the very least, a FSM if your gonna keep it awhile. Read, read and read, oh and throw in some search functions at the various jeep forums. There is not much that has not been asked on the ol interweb.

 

Great tip for creating a precise point of reference for measuring toe-in, Oswalla!

 

Gotta give credit to a Naxja thread I read some time ago. Must be good because I got 70k miles off my last set of BFG AT/KO'S.

I should of added that tire shops seem to always inflate my tires to 35lbs when they install them. I run mine around 30lbs, 35 is noticeably over inflated.

 

My door jamb sticker states 33 psi for 215/75r15.
That's 33 psi for a 28x8.5" tire under one of the lightest XJ's.

Larger volume tires require less pressure given the vehicle's weight stays the same. I run my 235's at about 30-33 depending on whether I want a softer ride or better gas mileage.

Honestly, 35 isn't a significant overinflation and lots of guys use similar pressure even in tires as large as 30x9.5-31x10.5".

 

Use 35-50 psi in LT sizes, Load Range C.

Don't confuse pressure and volume.

 

I run my LT235/75-15 General AT2s at 35 psi cold.

OP, can you snap a pic of your treadwear or at least describe how it's wearing? Is it cupping? How about wearing at the inside or outside edge? Middle? Even across the tread with no cupping, just faster than you'd expect?