Maximum backspace for a 18" X 9.5" wheel

Boxcars

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Sep 4, 2004
I'm toying with the idea of going to 18" wheels on my GN. The wheel comes in a 18 X 8 with 4.5" backspace I know I can use on the front, but would like to go to the 9.5 wheel on the rear, using 275 or 285 40s, but the backspace is on the larger model is 5.3". I think that's too much. Anyone know for sure? If I use a 7/16" wheel spacer, that would knock it down to under 5". Anyone know if that would that give me enough room?
 
I have 18x9.5 American racing wheels with 4.75 backspace. No issues using a 275/45/18 tire.
 
I have 18x9.5 American racing wheels with 4.75 backspace. No issues using a 275/45/18 tire.


Well, thanks! I think I got this. 4.75" BS will have to be my answer. Anything larger may cause fitment problems. Unfortunately, the wheels I was looking at only offer the 18X9.5 with one BS choice and it's too much. :sour: Back to the drawing board.
 
They would probably work with the .75 spacer you mentioned. I have at least 1/2 inch clearance between the frame and tire.
 
I'm toying with the idea of going to 18" wheels on my GN. The wheel comes in a 18 X 8 with 4.5" backspace I know I can use on the front, but would like to go to the 9.5 wheel on the rear, using 275 or 285 40s, but the backspace is on the larger model is 5.3". I think that's too much. Anyone know for sure? If I use a 7/16" wheel spacer, that would knock it down to under 5". Anyone know if that would that give me enough room?

Before you do that, check the alignment of the body on the frame.
 
I will do that, but I suppose I won't be buying new wheels at this time. I don't really need them, but the 17" X 8" wheels currently on my car I've had for 10 years. I'll probably just soldier on with what I have.
 
LOOKING FOR SOME ADVISE TO SEE IF THESE WHEELS WILL FIT MY 87 T-TYPE WITH STOCK RIDE HIEGHT.
FRONT
1885x120.650 OFFSET2.7 LIP
REAR
189.505x120.656 OFFSET3.54 LIP
FRONT TIRE 235/40/18
REAR TIRE 285/40/18
 
9.5" with 275 is right at the limit of what will fit without cutting stuff, especially if the car is lowered at all.

Do not take what you find on the internets as gospel before ordering. Get a wheel sizing worksheet and measure your car. They're all a little different, and at that size, there is zero margin.
 
With all stock brakes and suspension I was able to run 255/40’s on a 17” x 8.5” [4.5” B.S.] wheel on the front.

With the stock drum brakes and factory rubber control arm bushings on the rear l ran 285/40’s on a 17” x 9” [4.5” B.S.] wheel.
The tires rubbed the frame some on hard corners due to axle shift / rubber bushing deflection.
A .5” wider wheel with the same backspacing [4.5” B.S.] will pull the tire away from the frame .25”, which should be enough. I did not have the fender lips rolled or trimmed, but as Turbo6inKY says, it’s best to measure each car as they are different.

Here’s the fitment sheet HRE Performance Wheels uses.
F9B69D48-032F-477B-8746-917A46CFB9C5.jpeg


as well as an offset to backspacing conversation chart.
It assumes the overall wheel width is 1” wider than the rated width, which seems to be true.
6536C7DD-2D3A-4156-8EF0-A8433B050DF0.jpeg
 
With all stock brakes and suspension I was able to run 255/40’s on a 17” x 8.5” [4.5” B.S.] wheel on the front.

With the stock drum brakes and factory rubber control arm bushings on the rear l ran 285/40’s on a 17” x 9” [4.5” B.S.] wheel.
The tires rubbed the frame some on hard corners due to axle shift / rubber bushing deflection.
A .5” wider wheel with the same backspacing [4.5” B.S.] will pull the tire away from the frame .25”, which should be enough. I did not have the fender lips rolled or trimmed, but as Turbo6inKY says, it’s best to measure each car as they are different.

Here’s the fitment sheet HRE Performance Wheels uses.
View attachment 372872

as well as an offset to backspacing conversation chart.
It assumes the overall wheel width is 1” wider than the rated width, which seems to be true.
View attachment 372874
Thanks for the input. Will make some measurements
 
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