by megavega » Fri Jan 11, 2008 2:14 pm
simply place the car on jackstands placed under the rear axle itself, as low as you can, with the rear wheels off, use a carpenters square against the brakedrum/axle surface where your rims would touch it, transfer your mark to your garage floor. (I make marks next to the lines I draw on the floor like "ax" for axle, and "wwl" for wheel well) Then using some string and heavy nuts from a bolt tie the nuts to the string and hang them from the inside of the wheel well lip via a set of vise grips, transfer your mark from the nut to the ground (the string and nuts are just a plumb bob) do this the same for the inside wheel well.
Now move the car out of the way and you can now work with your marks on the floor as its a map to your actual wheel well clearance and your rear axle width. (you also can use a piece of cardboard and put the marks on that and not have to move the car if need be)
Its best to subtract 1 inch from each side of the wheel well to permit for body roll, this will keep the lips from chewing up the sidewall of the tires. I think youll find your not gonna be able to use more then a 8 inch wide rim, and your section width of the tire will need to be around 9.5" overall. You can easily see how backspacing effects the clearance both in and out, so if you know your wheel is 4 inch backspacing you can draw it out on the ground with your other measurements and know 100% accurately if it will work or not. This way when you go buy your rims, you know before you buy them if they fit or not! pretty easy.
Again, it matters the MOST as to the RIDE HEIGHT you have the car set at, if its sitting high you could use more width but it would need to stick out past the lips to do so, I have put the most rubber possible in a early vega, the pics in my build are actually a 245/45/17 on a 8 inch wide rim, but will need to have the lips trimmed to run them and then would only have a 1/4" of clearance,it rolls around without rubbing but you cant fit the first digit of your finger between the lip and sidewall. I am running a very stiff suspension with large rearswaybar, but I dont endorse my build ideas onto someone who isnt building the same type of goal, so I would say no more then a 235mm tread tire.
The rim width you choose will also effect the tires overall section width, the same 235mm treaded tire on a 7 inch rim will be skinnier then when on a 8 inch rim, the 7 inch will bulge the sidewalls out where as the 8 inch rim will make them more flat.
1972 hatchback, 28,000 orig miles, 427BBC/twin T4 turbo's/T56 six speed/big wheels, lowered down pro touring style-work in progress....
1973 vega wagon-under the blue flame knife.