Its time for new tires on the H3. My spare tire is brand new, zero miles, and I'd like to keep it and avoid buying 5 tires if I can. The spare is a bridgestone dueler 285/75 r16 (which I think might be discontinued, as I cant find specs for it anywhere; this size isnt even listed on the Bridgestone website). The tires I want to buy are the BF goodrich KM2 in a 305/70 r16, stated on the manufacturers site at 33.1" diameter and 12.2" wide.

So my question, then, is mainly about the H3s drivetrain...I know that you can't run different size tires because of the fulltime 4wd system, but is there even a little wiggle room? If I run the KM2 305/70 and one day get a flat and need to use my spare, is the slightly different height/width/weight going to cause problems? Obviously I wouldnt need to use the spare for any considerable length of time, but would it be safe enough to get me off a trail, or back across town to get home?

Thanks for any help.

 

The 285/75/16 is approx 32.83" diameter.
It would be OK to use it as a spare for the 305/70/16 tires, which calculate out at 32.81".
Every manufacturer is slightly different, as Goodrich claims 33.1"

Those are nominal diameters and the actual diameter may vary but would be well within range of each other.

 

X2 on everything Bunger posted.

 

Excellent, thanks guys.

 

there are some great videos on utube about open differentials, one by gm way back in the 30's when diffs were a new thing.
when you see those you will be less concerned about small differences in tire sizes.
any time you are not driving a straight arrow path, ANY turn, the tires are all turning at different speeds/distances. like driving around a parking lot!
locked diffs are for off road,mud,grass where the tires can slip when needed.
i read where a car got 2 sizes,left/right and they found out 10000 miles later. it was ok!
i wouldnt be concerned about an off size spare. in 90000 miles on 2 h3 i never had a flat!!

 

If your "new" spare is over five years old, it may not be safe to use.