Why no fit?

[RETed]

Originally Posted by vrracing

Doing the math:

Fronts:

8" wheel = 203mm
half of 203 = 101mm
40mm offset means
61mm to outside of wheel
141mm to inside of wheel

measured distance from hubface to outside of fender = 64mm
measured distance from hubface to suspension = 170mm

So our 40mm offset 8" wheel should be 3mm inset from outside of fender and have 29mm of clearance on inside.

Okay, let me add a few numbers...
On average, rim lips are usually around 1/2" or about 12mm, IME.
This is for "J" or "JJ" type rim lips.
See: http://www.carbibles.com/tyre_bible_pg4.html
(Scroll down about half way.)
I tend to add this 12mm to the (rim width)/2 + offset, and this should equal "backspace".
If this is a true 8.0" wide wheel, the we get 141mm + 12mm = 153mm.
153mm is right about 6.0".
So, your backspace on this wheel should be about that number...6.0".

I dunno where you're measuring the "170mm" number from, but if you're using stock type springs, the clearance issue is the lower perch of the front strut.
Some coilovers will interfere with the lower adjust collar or the bottom part of the spring, if you're using largish diameter springs.
Can you tell us where this 170mm measurement clearance is coming from?

At least with your fronts, you can play with a smaller / thinner spacer to get them to sink back in...
Try without a spacer and see if it'll fit?

Rears:

9" wheel = 240mm
half of 240 = 120mm
if we switch from a 20 to 40 offset...
80mm to outside of wheel
160mm to inside of wheel

measured distance from hubface to outside of fender = 90mm
measured distance from hubface to trailing arm = 170mm

leaving 10mm both inside and out.

That all sound right?

9" = 9.0 x 25.4 = 228.6mm, try more like 230mm.
230mm / 2 = 115mm (offset = 0)
115mm + 20mm (offset) = 135mm
135mm + 12mm (rim lip) = 147mm, which is our backspace.
147mm / 25.4 = 5.7874", which is about 5-3/4", backspace
Would like this backspace more inward, but the 9.5" wide wheel shouldn't get that close to the fender lip...
I've run 9.0", +35 with easily an inch more space to spare in the rears...
Your 9.5", +20 only adds another ~18mm less clearance outward to the fender lip...
Weird.


-Ted