I moved the springs inboard 3" on my 72 Demon probably 2 decades ago but have never done anything with it. Since I'm doing HRDW I figured now is as good as a time as any to finish it. The springs currently sit 7" inboard of the axle end flange the old ones were 3.25". I have factory wheels on it currently but do not intend to keep them. So I guess I'm asking exactly how much am I cutting of the stock housing? It's an a-body housing in it which I wont cut. I have a c-body housing that I'm going to cut down and eventually a D60. I don't have enough parts to do the 60 yet so I'm doing the c-body housing. Also I am sure it's been asked before but if anyone knows the biggest tire I can fit I'd appreciate it. For anyone that has done it what backspacing you're running with your wheels and how much did you cut off? One thing I think that's worth noting is I plan on swapping to a set of Wilwood discs in the rear.

Get a measuring tape and crawl under there. Figure out how wide you can go and what diameter will fit. A body cars typically need a short tire unless you make additional mods. You can probably fit a 10 inch wide tire in there but it won't be very tall, maybe 26 or 27 inches at most? The front lip tends to get in the way pretty quickly. Once you know how wide the tire can be then you can figure out which wheel you want. Then you can buy the tire and wheels and put them in place so you can measure the distance between the wheel centers.

If the additional mods you are speaking vaguely of is stretching the tubs, then know that in the plan. Also I was just under it tonight getting the dimensions I have thus far.

I just did a Duster. With stock tubs and wheel lips you can fit M/T 275/60x15 Drag radials on an 8” rim width. It required the front hangers to be spaced rearward 1/2”. Clearance is tight but it won’t rub anywhere. The width of the axle will depend on wheel off set. Get the tires and wheels you are going to use. Mock them up in the wheel wells. Measure the distance in between. Then figure drum or rotor thickness. Get the axle offset from what ever axle manufacturer you are going to use. You now have all the necessary dimensions you’ll need for housing width. I usually remove an additional 1/4” per side just in case. You can always add spacers. But you can’t get it any narrower.
Doug

Hang a plumbob on the inside of the outer wheel lip and one on the inner tub just in front or behind your axle, measure between the strings and deduct whatever you need for tire clearance and that will give you your tire carcass measurement and from there you can figure your wheel backspacing and what tire will work,do this with axle in the car, hope I explained that clear enough. Doug

I used this method on my Bbody as I ordered a S60 from Strange and had moved my springs in to the frame rails using Caltrac splits and I wanted a wheel that was an even split on the wheel front and backspacing and there was no extra charge to have it built to my measurement.

It really all depends on what mods you are willing to make. Moving the axle back, cutting the front lip of the wheel well, putting in tubs, removing the inner bulge on the outer part of the fender, etc. I had to do all of these and more on my Duster.

Take the rear out.

Obtain the wheel/tire combination you intend to use. Set it all up under the car with the wheels/tires exactly where you want them at ride height.

Measure inside of wheel axle flange to inside of wheel axle flange.

Subtract brake hat or drum thickness, and axle stick out. Axle stick out can change with housing end type. Result is housing width.

Anything else is guessing.

^^^^^^^^^ the correct way to find out for sure without guessing.
if you don't want to cut the wheel opening, spacing the forward spring hanger back a little also works. there are usually enough threads on the pressed in studs to go 3/8".

MoparX what do you mean by cut the wheel opening?

He was talking about trimming the front of the wheel opening of the quarter panel and outer wheel house to give additional clearance for taller tires. If you only need a little more room then you can space the spring hanger rearward like said by several people above. If you need more than that then and/or are your only option.

Thanks, It was a slant 6 car it has no value im not opposed to most mods

I already had my tires but wanted a very accurate backspace before I ordered my 15x12 wheels. I bought this tool. Use of the tool does require one to already have the tires they plan to use.


https://www.speedwaymotors.com/Wheel-Fitment-Tool-Tire-Fit-Size-Measuring-Mockup-4-Lug,508754.html?utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gad_source=1&gclid=EAIaIQobChMIjPq5x8qAhQMVSgOtBh1wXgOBEAQYCyABEgL4ifD_BwE

I had considered that tool

yes, trimming the wheel opening at the forward edge was what i was referring to.