What offset for narrowed rx-7 gsl-se rear end?

[GoldHawg]

I'm still not sure about wheel size for my Datsun. I have an Rx-7 rear end modified by Spriso to 47.5", so I know I can fit more tire. I'd like front's and rears the same, and want as much as I can safely do w/o rubbing. I plan on running Rota RBs, 15X7. What offset would work best for the front and rears to run say 205 50 15, or maybe even 225 50 15? Is there an online tutorial/calculation or really good thread that explains this? Thanks.

[RCMike]

Assuming you have not had a Panhard or similar fabricated, and are running the axle in the standard fashion on leafs; and assuming you have not pulled/flared the rear fenders, you are going to want to center the wheels in the wheel well in order to fit 205.. Larger will not really fit between the leaf spring, the frame, and the fender. You might fit larger at static display, but the minute you drive out a driveway or take a turn, you will have massive rubbing, both inside and outside.

[Alvin]

Is there an online tutorial/calculation or really good thread that explains this? Thanks.

boom!
http://www.1010tires.com/Tools/Wheel-Offset-Calculator#



I highly recommend the trial and error approach. Grab some wheels lying around and a ruler and it will be much easier to gauge
Also worth noting...with your narrowed rear axle it's now a bit more involved to run a square setup. What fits in back may not fit up front now, especially with comp springs!
ie that 225/50/15 tire will most likely not "work" up front.

[Alvin]

edit, lol just remembered an example I've posted a bagillion times!
This is a 15x7 0 offset Konig Rewind with a 205/50/15 Hoosier slick. Though these tires run on the wider side, it's clear that they don't fit up front while in back they now do.





Offset is important, but also varies between wheel/brand with respect to the mounting pad/spoke design.

[RCMike]

Alvin, you have a 4 link system to keep the axle straight, right? It does not move side to side on your car?

[Alvin]

Alvin, you have a 4 link system to keep the axle straight, right? It does not move side to side on your car?

Mike I have a Panhard Rod for lateral location...a must-have on 4-links.

[GoldHawg]

Alvin
Thanks for the link. It is helpful to see the direction of the offset. Also your pics were great. I'm guessing that since I have a narrowed rear end, I'm probably safer getting the standard +12mm offset on both sets and go with an initial set of 205 50 15s.

[fj20spl311]

I though the narrowed rear ends were so people could use "0" offset wheels.
I looked up the standard width 48.625" yours is 47.5......so the difference is 1.125 or 28.5 mm.
Half of that needs to be subtracted from the offset......"0" offset wheels should have 2.25 mm more clearance from the fender than +12.

Plus 12 could be the correct offset for 205/50x15 as they did not fit with my +12 without a little work.

[spriso]

+12 will be perfect with your setup Jeff.

Michael