Quote:
Originally Posted by Houston54
You will need to measure the side to side distance from the inside of one fender well/tub to the other. Then measure the distance from the wheel mounting flange side to side on the axle you are using. Subtract the fender dimenstion from the axle dimension and divide by two. This is the space you have available to fit your rim and rubber into.
Typically tires extend past the rim about one inche and you will also want about one inche of clearance between the inside sheetmetal and the rubber.
In the case of a stepside bed the following is how it works out with a 2nd gen F body axle.
Outside bed width = 50"
Axle width flange to flange - 60"
Max side to side space = 5"
Subtract 2 inches for tire width and inside clearance
Proper backspacing is 3"
Of course we do not live in a perfect world and finding rims with the proper BS without going custom is difficult but that is while spacers are used for. Just don't go too thick on the spacers that your lug nuts do not fully thread past the head.
So to get it right for your application I would suggest getting the tape out and sizing up what you have. You should be able to work it backwards easily enough to see what size tube you will need. The 12" rims will not fit without some added clearance. Remember not to put the rubber too close to the outside sheetmetal or you could cut the sideway on turns where the suspension is in compression.
I try to maintain at least one inch of clearance on both sides of the tire. Some say that using a rear sway bar allows you to cut this down some.
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very useful info you gave there much appreciated thanks
