Just got a good deal on chrome H2's and plan on runnin 285 70 17's. I had 285 75 16's on my last gasser and never thought twice about the spare being smaller (open rear end). Could I run the stock 245 spare if one of the 285's got a flat? Or would this wreck havic on the locking rear? Also, size wise how does the 285 70 17 compare with the 285 75 16?

In your case, you can run the stock spare on the front only. Even then you CANNOT use 4-wheel drive.

Worst thing that can happen is that you will have a flat on the rear. If that happens, you will have to take a good tire off the front and and replace it with the spare. Then use the tire from the front to replace the flat one on the rear.

Of course, most flats happen on the rear anyway.... Something to do with the front tires throwing stuff into the rear tires. Just be prepared to do a three way ... spare to front, front to back, back to bed.

L8r

Why can't you run the spare on the back and use 4X4? Later! Frank

mismatch sized tires with a locking diff is a bad idea. the 285/75/16 to 285/70/17 is not so bad, still within the safe zone. you can tear the rear diff up by running tires of differing sizes. Save a 285/75 as your spare and be done with it.

Why can't you run the spare on the back and use 4X4? Later! Frank Frank,
the spare is 7% smaller in diameter...the diff needs to make up for that.
Will work for short distances...to the diff it is like driving through a turn.
No matter where you mount the spare, the diff of the axle where the spare is mounted needs to make up for the difference.

Also, size wise how does the 285 70 17 compare with the 285 75 16?
redneck45,

try this link:

http://ejelta.com/tiresize/index.html

The difference is that you loose about 1/2" of sidewall.

That was being a little facetious. I also have the G80 and 4X4. The Eaton is suppose to lock up when it sees 100 RPM difference between axles. Basically an open axle until then. Just my opinion, I don't think it is going to hurt anything to run the smaller tire to the nearest tire shop. It won't hurt the four wheel drive either as long as you are on a loose surface. Later! Frank

Ok, do they make a 285 75 17? I just picked 285 70 17 cause that is what people on this board are runnin on the H2's.