whats the difference in the
315x70R-17 and a 35x12.5x17

 

check the load ratings, they may be different, the physical weight of the tire as well.

 

You probably wont notice a difference. I have run both sizes on my rubi. The metric size is OE for H2 hummers. They are typically 8-ply. Most 35's are 8 or 10 ply. I would stick to the lower load rating for the ride. The lower rating also conforms to rocks better when aried down.

 

aren't most 35s a bit smaller than they claim to be? As with every other tire.

 

yup, you are correct. Tirerack has a pretty good chart to give you actual measurments and they tell you what size rim they measured it on too.