Help me verify backspace math
 

Let me clarify,, trying to make sure I have enough space between inside face of rim to spring.

Looking at a new rim/tire setup as everything is on sale and I need new tires anyway. I need to make sure I don't rub the springs up front (no coils). Don't worry about poke

Current setup 17x9 +40 3MM spacer up front 245/40/17 tire 9.8 cross section

Thinking 18x10 + 15 285/30/18 tires 11.4 cross section


Going to work off the tire cross section (sidewall to sidewall) number as it's larger that the rim.

Backspace = (9.8/2) + 1.57 (+40MM offset) + .11 (3MM spacer) = 6.58


Backspace = (11.4/2) + .39 (+10 offset) = 6.09 or

Backspace = (11.4/2) + .59 (+15 offset) = 6.29


Math good? Or should I subtract the spacer in first equation which would then be 6.36??

I stopped reading partway through. There is no way to fit that size wheel and tire with stock front fenders, even with coils.

edit: try https://www.ft86motorsports.com/wheelitfit/

I also attached a pic showing your planned new setup and how far it sticks outside the front fenders.

edit2: if we're looking purely at clearance to the front suspension, your new setup will clear the spring perch. But you'll have bigger issues with the front fenders.

Thanks for your thoughts,,, nice tool as well. Haven't seen that before.

The issue I was concerned is will it clear the springs and didn't want to order the wrong rims. I'll be adding some flares if this happens so the 'poke' isn't an issue.

You will have almost stock clearance according to the website linked above.

Look at post# 1009,
http://www.ft86club.com/forums/showt...=41083&page=73


and Post# 1068 (guy now has 295's square!!!!!)
http://www.ft86club.com/forums/showt...=41083&page=77

Yep, with the necessary added front fender width. It should be noted, though, that Patrick's wheels would not have cleared stock suspension.

He sold the car, though. Shame.

Thanks again guys,,, bought some Forgestars yesterday

Nice! What spec Forgestars did you order? Offset?

F14's 18x10 +10 and they'll run 285/30/18 tires. Saved almost 15% with black Friday sales. Unfortunately that tires size doesn't have a ton of options,, but P-Zeros are on the short list. Need to decide on flares still,, like these , they're out of the UK, vendor said these were 18x10 +20's.

Check out these flares. I think that they look better! (and may be easier to get) Pics with FORGESTARS!
Post# 3655 & 3656
http://www.ft86club.com/forums/showt...25171&page=262




Post #6 "I got them from zgfenderflares.com"
http://www.ft86club.com/forums/showthread.php?t=104522




EDIT: Double checked my links.... they are Datsun 240z ZG flares




Under $200 shipped seems like a good deal for all 4.
http://zgfenderflares.com/

Those are in the running and I've been studying them. His set up is a bit different:


Wheels: Forgestar F14, super deep concave all around
Tires: Hankook Ventus V12 EVO K120
FR: 18x9.5 +5, 245/40
RR: 18x11 -6, 285/35


When I do the math measuring centerline of wheels to outside edge I get:


His Front 4.56"
Rear 5.73"


Mine Both 4.61"


So poke on the front is about the same,, the rear I'm 1.1" less.


The front flares look a bit small width wise as compare to the tires,, rears would be too big. 4 Rears might work,, but I'd need to modify them a bit,, which is doable. Looks like I could do 4 rears for $240.





There is also the N-Style look nice but again they get expensive at $700. Site says car is running 18x10 -5 front and rear.

Did you see the tab for these on the other site? They are 2" front and 2" rear flares. The flares on the car with the 18x11's are 3" on the rear. So, if yoru wheels are 1.1 less rear, these might work...


http://jdmfenderflares.com/