17x10.5 in the back?
 

Is it possible to run 10.5 without rolling the fenders or changing any of suspension...?

What size tire?

Mr rx-7 tt
That might really depend on the wheel choice, and wether you can pick a specific offset or not. 10's will fit w/ no mods. Mine were 17x10 +44's. The rim cleared the trailing arm by more than 1/2", but the 275/40/17 tire itself was close. You'd want the same FRONT spacing as that wheel, with most/all the width added to the inside.

What size tire are you trying to run that would necessitate that size rather than a 10? You may actually have more clearance around the trailing arm w/ an 18x10.5.

I know I can get 10 but I would like to get 10.5... 275/40/17

you do realize that a 275 will fit just fine on a 10 inch wheel right? i'm putting 285's on my 18x10's

mr rx-7 tt,
It CAN be done.

I've personally seen a set of 17x11s on the rear w/ a 275/40 hoosier. The wheels were CCW's. I'd give John Purner a call there, as he should be familiar with the fitment (i believe it was originally done for Brad Barber, and included a 17x10.5" wheel for the front w/ a 275/40 tire that also fit the rear)... it required upgraded trailing arms with spacer washers, 2.5" coilovers and is TIGHT. 17" actually are a tougher fit than 18's because of the trailing arm. If you go down to 10.5's it should add enough room for comfort...

I'll dig through my email for you and see iof i still have the backspacing info (i asked).

Here's the set i spoke of:

http://www.negative-camber.org/crispyrx7/ccw.htm

shit, won't 275s fit on a 9" wheel?

They *will* but tire engineers will always tell you that tires will work better at the higher end of the recomended rim width range... to the extent that you might be better off with a 255 or 265 that fits well on a 9" wheel rather than stuffing a 275 on it.

Not all 275's are created equal either... some are really wide and look ridiculous on a 9" wheel. I've got 255's on my 9" fronts, and 275's on my 10" rears... they look perfect to me.

Yeah, I know it wouldn't be optimal.

I'll be running 255s all around on 9" wheels, but I'm in an FC so you guys don't care ;)

i had 275/40/17 nitto 555RII's on my 17x9's looked a little big but looked mean :)

Ptrhahn,
Thanks for the time you spent with the link and for your input.