Flush +/-
 

Hey guys, I know that some of you out there are experts with this wheel spec thing. I think it would be nice to know what offset matches with each wheel width for a perfectly flush TDC (top dead center) fitment front and rear on the BRZ/FR-S.


I don't think I need to list the widths for each wheel diameter because the flushness should be the same whether it is a 16" wheel or a 20" wheel. (obviously there might be fitment issues for some diameter/width/offset combos, but we will tackle those when we find them.

So, I think this should be an easy chart to fill out. If you have a wheel on your car that is LTF (less than flush, I patent that!) and you know the offset, then you can simply measure the millimeters that would need to be added to the top of the wheel to bring it perfectly flush with the top of the fender opening and subtract that number from your offset.

We'll have to do this for STOCK HEIGHT because lowering affects the camber and that will change things. The 2nd step is to measure how each 1/4" drop affects the flushness of the top of the front and rear wheels so we can predict flushness with a drop.

Lemme know what you think.

this is a good idea, but the tire selection also affects flush-iness

good for a rough measurement.

Good idea.

Well, once we have the wheel width and offsets roughed out, we can then throw out proper tire dimensions that would be appropriate. :)

This. This is gold, i hope someone pitches in!

:bump:

All we really need is a consensus on how many millimeters need to be subtracted from the stock wheel offset to get perfectly flush. My car isn't stock anymore, so if nobody posts I will have to drive to the dealer with my ruler. :)

Once we have that, it should be really easy to just calculate flush for different combos using the Wheel Offset Calculator.

Ok, just visited a local dealer and measured a bone stock car. Found that the front wheels are 23mm LTF and the rears are 30mm.

So, if the stock wheels are 17x7.0 +48 then we would need a 17x7.0 +25 in the front and +18 in the rear for perfect flushness. Any arguments? Someone check my math, haha.

Your calculations are right. If your measurements are right as well you need the following offsets to be flush:

7.5" F: +31mm R: +24mm
8.0" F: +38mm R: +31mm
9.0 F: +50mm R: +43mm
10" R: +56mm

Feel free to check my calculations. I have used the offset calculator. I might be 1-2 mm error due to rounding. 1 inch is 25.4 mm.

If you don't want to go with different offsets in front and rear a 7 mm ~ 1/4" spacer in the rear is an alternative.

OK, I completed the chart at the top of the page, now we just need to account for lowering. Does anyone have a car that is lowered with stock wheels on it? If we get measurements from that then we can probably extrapolate from there.

I continued this in the suspension forum:
http://www.ft86club.com/forums/showthread.php?t=13083

So question: if we take the 18x8 RPF1 for example, which comes in a +35 and a +45. If I want a nice fit but not TOO aggressive, would it be good to go +35 in back and +45 up front? Thanks.

So for an 8" wide wheel for perfect flush:
Flush Front: +38
Flush Rear: +31

So with your +45 in front you will be sunken about 1/4", and in the rear it will be nearly flush, a little more than 1/8" sunken. Should look pretty good.

I always used this website for fitment on my other car

http://willtheyfit.com

Hopefully this helps a little bit!

I forgot about that site... I will add that to the useful links!