Quote:
Originally Posted by olah.inc
does a 17x9+0 wheel with 255/40s fit under a 20mm s13 fender? (front)
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I'll use Olah's question as a real world example on how to figure this stuff out. Hint... If anyone asks this question again, they are admitting that they don't know how to add and subtract.
From before:
Max backspace Front 150-159mm
Max Frontspace
Front 95-105
Olah's preposed backspace
(9x12.7) + (0 offset) = 114.3
Clears by a mile on the inside. Unless he just wants to look cool with mad flushness on his overfenders, he better add some offset.
Olah's preposed frontspace
(9x12.7) + (0 offset) = 114.3
Max frontspace is normally about 105 with some camber and stretch on the front of an s13. Add 20mm over fenders, and if you want your tires to be on the inside of the fenders your frontspace better be <125mm (105+20).
Olah's 114.3 frontspace will definitely put him flush/inside his 20mm front over fenders.
Summation:
Yes they fit, but with some more offest and a wider wheel there is room for more!
How to calculate the true MAX!!!
Take the max backspace and add that to the max front space plus any overfenders. In Ohlas case that is:
150 + 95 + 20 = 265mm wheel width
159 +105 +20 = 284mm wheel width
devide by 25.4mm/in to get the numbers you're used to looking at.
265/25.4= 10.4" wheel
284/25.4= 11.2" wheel
I've already explained how to calculate offset, but one more time:
let's take a 10.5" wheel since that will be the closest/easiest thing to find in the realworld
10.5 x 25.4 = 266.7mm wide wheel
266.7/2= 133.35
width devided in half gives you the backspace of a zero offset wheel.
since we need the backspace somewhere between 150 and 159, that means the offset will become
159-133.35= 25.65mm
150-133.35= 16.65mm
You can either order a 17or18x10.5 +16 and probably be safe, or go for the full monte and get +25 and run the risk of possibly needing a spacer depending on how much rubber you want to run, the width of your coilovers, etc.
Remember, if you want to go with the 284mm wide wheel you are going to be pushing it. You'll probably have to have a very exacting alignment and a bit of stretch to make this work. 265mm/10.4" wide wheel is STILL pushing it, but you'll have a little more wiggle room.
The question now becomes how much rubber can I run?
This chart might be helpful. But remember that if you're pushing the limits and using max frontspace (especially) and max backspace you may need to go wheel width in mm + nothing (rather than plus the 20-40mm).
Wheel Tire:
inches/mm + 20-40mm usually is fine
7 177.8
7.5 /190.5
8 /203.2
8.5 /215.9
9 /228.6 w/ 245-265
9.5 /241.3
10 /254.0
10.5 /266.7*** w/ 285-305J
11 /279.4
11.5 /292.1
12 /304.8
So Olah...
How bout a 18x10.5 +16 with a 265 (maybe even a 285) tire!?