235x75X15 VS 31X10.5X15
 

Hi all

This may be a pretty dumb question, but I could not find anything on the site. I have read everything about cranking the torsion bars and shackles, already done. How much more lift will I get going from 235x75X15 to 31X10.5X15

Roughly .9 to 1.4 inches.

31x10.5x15 is equivalent to between a 265/75/15 and a 265/80/15 (if it exists). According to miata.net's tire size calculator, those sizes show a sidewall of 7.8 to 8.3 inches. Take that and subtract the stock (235/75/15) sidewall of 6.9 inches and you get .9 to 1.4 inches.

Of course this is all dependent upon the manufacturers actual numbers as some 31" tires aren't true 31" but could be just over 30".

So then do I need to put on a suspension lift?

Divided by two? or did you already do that??? (1.05) :D

Lol.... Not very much, I would be more worried about them actually fitting....

Try googling a 'tire calculator' oh heck ... here http://www.1010tires.com/TireSizeCal...bmit&reset=yes

Keep in mind that this is just a general rule of thumb. Hardly any tire that says eg: 31 x 10.50 is actually 31" tall or 10.50" wide at the tread. You may have to go to the manufactures website for specific dimensions.

<edit> & I'll edit my post to say uhhh yeah TBB, I agree?! lol

Edited my original post to explain. Sidewall minus sidewall would only be 1 side since extra sidewall on top of the tire wouldn't contribute to lift.

I thought you already did torsion bars and shackles? Or did you just already search it? If you haven't, then read the many threads on the subject already in existence. If you did, then you SHOULD be fine. Rim backspacing and offset will determine if you rub. Every truck is different. Or I should say that every truck's torsion bars are different.

My undrestanding is I will need to do some trimming for the tires, no problem with that, I have some experience lifting a Jeep. Just cant spend to much on this (lack of $$$)

I already cranked the torsion bar 1.5 inch (both done the same). I was just hoping to get a little more clearance then approx 1 inch but actually that is what I was expecting.

Thanks

I think I will have to still do some trimming to fit 31's

FWIW, converting the metric size to inches, 235/75r15 is 28.87" x 9.25" x 15", compared to 31x10.5x15, that's a 2.13" height difference and 1.25" narrower treadwidth. Since you're wheel is only resting on one sidewall, you halve the height difference for 1.065" total height gain.

That's all based on the premise that a given tire is the exact size they say it is (which is generally untrue)

for the 31x10.50x15's installed on my 2000 Envoy w/stock rims, i have to do the shackle/torsion bar and a P.A. 2" body lift, and some minor trimming on the rear side of the front wheel openings