Quote:
Originally Posted by TX3100Guy
I'm thinking of moving to a wider 7" Cragar wheel. It has -6 offset, which is a full 12 mm difference from the +6 I have now.
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no, thats only going to be an additional 6mm. thats why i tried to explain the difference in offset and backspacing but i guess I did it poorly.
when you make the wheel wider, the extra width is spread equally over the front and back halves of the wheel. so a 7" vs a 6" will have an extra 1/2 inch on the front half of the wheel (wheel mounting surface to the front lip) and 1/2" on the back half of the wheel (wheel mounting surface to the rear).
so going from a +6 to -6 will be a 12mm (1/2") difference in the mounting surface to the center of the wheel, but the actual gain in backspace is only going to be:
8/2 -1/4 (-6mm) = 3.75 backspace
and
7/2 + 1/4 (+6mm) = 3.75 backspace
zero. there will be no difference in the backspace, all the extra inch of the wheel width change will be on the front side of the rim, 1/2 inch that was already on the front side + 1/2 inch in offset change.
also, and this is kind of important to put all the way down here at the bottom but cest la vie, if the caliper right now is hitting the CENTER of the wheel, a different offset will not fix it, only a spacer will. if the caliper is hitting the rim portion of the wheel, a different offset may fix it. a different style wheel with a different center shape may fix it too.
and finally its worth mentioning, if you have the room for the extra 1" wider wheel to have the extra width all the way on the front side.... just get some 1.25" spacers and dont worry about new studs, it will move the wheel center out away from the caliper for about $50.