Wheel Offset for '71

thought of something else also. Will changing from drum to disc change the needed backspacing?

Just jacked up the car. looks like the 14x7 that is under the car now is 3

1/4 inch backspacing. That is leaving me about one inch between the tire and the upper spindle. So am I to assume that if I stay with a 7 inch wheel I will need the same backspacing, and if I go up to an 8 inch wheel I will need to add an inch to the backspacing?

Just how much movement is in the sidewall of a normal size tire (not low profile) in the middle of a corner with a stiffer than normal suspension? I would rather be safe than sorry.

"Scott Van Nest" wrote

Here are some known good combos for 15" wheels on a '71-'73 ("bs" = backpace):

15 x 8---4.5 bs---235/50R15 frt---265/50R14 r---OE frt, "helpers" on OE r springs---OE disc/drum 15 x 7---3.5 bs---225/60R15 all round---620 lb/in frt, 5-leaf std eye r springs---OE drum/drum 15 x 8---4.5 bs---245/50R/15 frt---245/60R15 r---620 lb/in frt, 4-leaf std eye r springs---OE disc/drum

15 x 8---5.5 bs---275/60R15's will fit on the rear but will rub on large bumps with OE springs. 5-leaf springs may cure this.

That depends on the discs. Wilwoods are infamous for messing up backspacing, front and rear. OE, no problem, discs are the same as drums.

This question suggests some confusion about backspacing. Backspacing is the distance from the lug flange to the INNER rim edge. If you go to a wider wheel without changing the bs, it's the OUTER rim edge that will grow, so it's fender lip interference you need to be measuring.

When eyeballing ball joint interference, keep in mind that the 15 inch rim will increase the horizontal gap to the ball joint by one-half inch. However, increasing the backspacing by one inch will close the vertical gap by one inch. These relationships make it possible to increase the width to eight inches or more, by using a larger diameter rim, so that the ball joint nests inside the rim.

Don't know on that one.

180 Out TS 28

I have 15x10's on the back of my 72 Mach 1 and they have 4" backspacing. If my fenderwells weren't rolled, they'd rub.

I'm getting 17x11's and I'll be getting 6" backspacing. I measured multiple times and figure that a 6" backspacing is about max (both sides) on the back tires. Now, on the front, I don't think I'd go more than 4" backspacing.

My $.02.

Jay

Jay - You have any pics of that backend with the 10 wheels? I would also like to see a side profile with the 17's when you do that. I am/was considering 16 inch cragar's, if the resources come available. I think 16's will look nice, but am not too sure what 17's look like.

There are various links to various pages from there.

Jay