My HS auto cl*** (Coastline ROP) recently received a grant from the Collectors Foundation www.collectorsfoundation.org We`re building a `66 F100 longbed mild street custom and have a couple of wheel offset questions. I`ve been checking a lot of forums but this is the one to go to. Would like to go 10" rear rims w/275 or 285R15 on the rear, 4-4.25 backspacing. Think that combo should fit. It`s the fronts that I question. Would like to go 235/60R15 (running stock drums) Any thoughts on the backspacing? Not much info on that. We are lowering it - 3" rear, 4 front (DJM kit) We can even go 16`s to get a better selection. Any ideas? BTW, the 353 Bebe Canepa car build is still in the works - dealing w/shool district policy and the BS has added 10 years on my lifespan. Thanks guys
Don't forget about the front spacing. That is the clearance side that you actually see when looking at a car. Front spacing is very important, but wheels are built to a back space spec. (I believe, because that is the side the center is pressed in from during ***embly.) To figure front spacing, measure TOTAL RIM WIDTH (including lips) minus back space dimension. TOTAL RIM WIDTH will be greater than Rim Width because it includes lips. Back space is usually measured from the outside of lip. Next, to do the job right, include the bulge of the tire in both spacing measurements, so that you consider that in figuring clearance, both back (inside) and front space (outside the wheel). You can spread the tire to the rim width and measure the section width to help in the math involved here. Sometimes you can get section width on different width wheel info from the manufacturers. Measurements for total back and front space can be measured from a straight edge on wheel mounting surfaces. Turn front wheels and measure in and out with the straight edge about as far out as the tire diameter. Body and suspension restrictions will dictate what tire and wheel can be used without interference.
if your using the stock width rear axle you can fit about 5.5 inches of front spacing on the rear so a 15x10 with 4.5 or 5 inch backspacing would be best. i was planning a 275/60 15 on a 15x8 rear and a 225/70 15 on a 15x7. should be about perfect with the djm drop kit (same as mine) im not gonna run the wheels any more but they are for sale! nos ET mags in the original bolt pattern. hope this helps matt
they are measured by backspacing because that is where you make contact(rub) other parts of the vehicle---has nothing to do with the manufacturing process...
So what about where the front of the wheel and tire interface with the inside of the fenderwell? Surely, all the wheels and tires on your vehicles don't stick out past the fenderwells.
So is that why you can put any size tire and wheel on the rear of a tri-five Chev? Yea right. Maybe there IS a little more to consider. Let's get back to trying to help the teacher. One thing is for sure, you have to measure, then, you have to do the math. When you know what back and front spacing you need, then, you know what to look for at swap meets or online. More than a few times, you will be looking at wheels that are for sale because the owner, or someone, did not measure or do the math. Remember that all wheels have a total width nearing 1" wider than the rim width. Back space is measured from the outside of the lip, which DOES affect the front space dimension. Front space=total width (not rim width) minus back space. Do not forget about the tire bulge in your measurements. Sidewall bulge will be where most rubbing will occur.
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