Wheels for a duster offset and backspace
When I bought my Dart Sport, it already had 18s: 225/40-18 in the front and 245/35-18 out back. I have no idea what backspacing is on these wheels (is there an easy way to tell?). I'm thinking I'd like to run all four of the same size wheels/tires so I can rotate tires and only carry 1 size spare. Ideally I'd probably like 17's but I read that 18's give you more clearance for front suspension items. Could anyone share their experience with one size for all 4 wheels/tires? Thanks
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Easiest way to determine the backspace is shown in the video I posted above, pull the wheels and measure from the outside of the lip on the wheel on the backside to the mounting surface. The rims may also be stamped or marked on the inside, but that will probably be an offset number.
The problem is that with an A-body the backspacing needed in the front and in the back isn’t the same. The wider the tire you’d like to use, the more that’s true. So, to use the same rims front and rear limits your width.
The other issue is the rear axles aren’t all the same width. A-body 8 3/4’s are wider than A-body 7.25 and 8.25 rear axles. So, what rear axle do you have?
I’m also assuming you have the 5x4.5” bolt pattern since you have 18’s already.
I still don't understand why a person would worry about offset, the back space is what really matters for wheel fitment ,if the back space aint right , it wont work if ur pushing the limit on wheel/tire size.
I have to have a 3 1/2" back space with my rear end length, and tire / wheel combination, I could care less about the offset in mm measurements.???????
That’s because you don’t understand what offset is telling you. Offset references the centerline of the rim. More importantly, it doesn’t change when you change the width of the wheel.
So, if you did your homework and centered your wheels in the wheel wells, but want to change the size of your rims or tires, you just get the same offset rim. For example, you have 17x8’s and want to get 17x9’s and you have the same clearance at the spring and the quarter. If you have 0 offset 17x8’s, you just get 0 offset 17x9’s, the wheel stays centered. Those rims don’t have the same backspace, the 17x8’s are a 4.5” backspace, the 17x9’s have a 5” backspace, but the offset is the same.
Offset just uses the centerline of the rim as it’s reference point, backspace uses the outside of the lip on the back of the rim. Both are really useful in determining what fits your car, but offset it especially helpful if you’re comparing different width wheels.
