Inside of rear tires wearing out faster that outside?

The inside of my rear tires are wearing out a lot quicker than the outside. It's only on the rear tires. Whats causing it?

 

The rear of your truck is a lot lighter than your front therefore you need to adjust your air pressure accordingly. Currently it's too high causing the tire too balloon and wear on the center.

Edit: Here is a bit more

http://www.2carpros.com/articles/how-car-tires-work

 

x2

 

Photos?? Cause center wear and inside wear are different...

 

I read the OP to mean the inside of the tire as in the portion closest to the centreline of the truck, not the middle of the tire. In which case, my guess would be alignment.

 

That is what I got too...but that doesn't really make sense since the rear is not adjustable... but the overinflation thing is a valid guess I think...just depends on what the tires look like.

 

Tires have 5 tracks of tread...dead center and the 2 immediately beside it are wearing.