Duster - Suspension/Wheel/Tire Combo Question

[Wilson340]

I need help in determining if the following wheel and tire set up will fit under my stock 73' Duster rear fender and not rub against the stock located CalTrac leaf suspension. Any help would be appreciated. My concern is that the 4.875 backspacing might be too much and cause it rub against the leaf springs. Thank you.

Wheels: Centerline 15x8.5" with a 4.875 Backspacing
Tires: P275/60r15

 

[72bluNblu]

Depends entirely on what rear axle you have. If it's a BBP 7.25 or an 8.25, it won't fit. Not even close.

If it's an 8 3/4 with BBP axles it will probably be too close to run on the street without some rubbing, but a small spacer (1/8") would probably be enough to clear them.

 

[Wilson340]

Thank you for the feed back. I have a 8 3/4 with a SBP. I'll have to look into spacers. Any real safety issues with running that small of spacer?

 

[72bluNblu]

Thank you for the feed back. I have a 8 3/4 with a SBP. I'll have to look into spacers. Any real safety issues with running that small of spacer?

There are no real issues running small spacers (1/4" or less) as long as you have the proper thread engagement on the studs/lug nuts. There are arguments for having hub centric spacers vs being lug centric, but quite frankly many cars and wheels are lug centric.

But, to address your bigger issue- SBP axles change your clearance. SBP axles have less flange offset, which means you won't need a small spacer. You'll need a spacer that's at least .375" if not larger, and that's more than I'd run. I generally draw the line around a 1/4" spacer.

 

[crackedback]

According to a spreadsheet that I did years ago, with an 8.5" wheel, 4.81" backspace centers the it up in the wheel well.


That's stock SBP 8.75 std length

Not having the spring moved and a 275 tire is going to be a tight fit no matter what.

 

[72bluNblu]

According to a spreadsheet that I did years ago, with an 8.5" wheel, 4.81" backspace centers the it up in the wheel well.


That's stock SBP 8.75 std length

Not having the spring moved and a 275 tire is going to be a tight fit no matter what.

I think it’ll be tough with the SBP axles with that much backspace.

But, to be completely fair I’ve converted all of my cars to BBP before I’ve maxed out the tires/rims. So I don’t have as much hands on with the SBP clearances. I’m using measurements on the SBP axles to convert what I know works with BBP to a recommendation for SBP, so there’s more room for error.

275’s are a pretty tight fit, so taking measurements on your own car is definitely the best policy as not all of these cars were identical. A 1/4” either way isn’t uncommon, and that makes a big difference when you get down to the minimum clearances which is what happens with 275’s.

 

[Wilson340]

Thank you. I appreciate all the input.

 

[DemonK9]

'73 Duster, cloned to a '71 (tail panel, front clip), 7 1/4 rear end: You can fit 295/50/15 on the rear, as pictured here. Not sure of the backspacing that the rims had though. Tires would only rub if they bottomed out going up into the curve of the fender well (if you get what I am meaning to say...lol). Had air shocks on rear to stiffin' it in the rear to prevent it from bottoming out on bumps with a load (2 people) in back.......so, you can fit up to a 295 with minimum rub issues.

 

[Clelan]

I have a 74 Duster with exactly that wheel and tire (Centerline 15x8.5" with a 4.875 Backspacing and 275-60-15 Mickey Thompson drag radials). It has an A body 8.75 rear with a big bolt pattern conversion. That tire on that rim fits perfectly for me. I have uncut fenders and stock location super stock springs.

I know the big bolt pattern conversion adds a bit of width but I forget how much. I'm sure a small spacer will set it right for you! I wish I took better photos of that clearance I have.

Cley

 

[famous bob]

There are no real issues running small spacers (1/4" or less) as long as you have the proper thread engagement on the studs/lug nuts. There are arguments for having hub centric spacers vs being lug centric, but quite frankly many cars and wheels are lug centric.

But, to address your bigger issue- SBP axles change your clearance. SBP axles have less flange offset, which means you won't need a small spacer. You'll need a spacer that's at least .375" if not larger, and that's more than I'd run. I generally draw the line around a 1/4" spacer.

Dont fret I`m running about 9/16" spacers w/ 295 60 d15 treaded slicks on the street , I do have full engagement of aftermarket 3" long studs tho.

 

[Demonic]

Nice look with the Hurst and Duster emblem! Very cool.

 

[72bluNblu]

'73 Duster, cloned to a '71 (tail panel, front clip), 7 1/4 rear end: You can fit 295/50/15 on the rear, as pictured here. Not sure of the backspacing that the rims had though. Tires would only rub if they bottomed out going up into the curve of the fender well (if you get what I am meaning to say...lol). Had air shocks on rear to stiffin' it in the rear to prevent it from bottoming out on bumps with a load (2 people) in back.......so, you can fit up to a 295 with minimum rub issues.

View attachment 1715470517

Only with the rear end jacked up in the air like yours is. And, if it rubs over bumps, or loaded, or going around a corner it means the wheels don't fit. Wheels that fit don't rub.

I run a 295/35/18 on the back of my Duster as well, but my car is lowered so the wheels actually have to fit inside the wheel wells. It takes a 1/2" spring offset and another 1/2" trimmed off the quarter lips to do it, and even then barely. Sure, if you run air shocks and destroy your shock mounts you can run darn near anything. Doesn't matter if they hang a 1/2" out of the wheel wells if the back of the car is 3' in the air.

I have a 74 Duster with exactly that wheel and tire (Centerline 15x8.5" with a 4.875 Backspacing and 275-60-15 Mickey Thompson drag radials). It has an A body 8.75 rear with a big bolt pattern conversion. That tire on that rim fits perfectly for me. I have uncut fenders and stock location super stock springs.

I know the big bolt pattern conversion adds a bit of width but I forget how much. I'm sure a small spacer will set it right for you! I wish I took better photos of that clearance I have.

Cley
View attachment 1715470522 View attachment 1715470523

The BBP conversion adds between 5/16" to 3/8" to each side, which is a decently big spacer to run. It looks like your wheels are nicely inside the wheel wells (good job!), which means they're also fairly close to the springs. Which also means the OP will have to make up all of that space with a spacer. Personally I don't like to use spacers that are more than a 1/4" on the street. Obviously they make larger spacers than that and people run them, but that's the rule of thumb that I use.

Dont fret I`m running about 9/16" spacers w/ 295 60 d15 treaded slicks on the street , I do have full engagement of aftermarket 3" long studs tho.

View attachment 1715470527

And your wheels hang a good 1/2" outside the quarter lip too. If your car was anywhere near stock ride height those tires would rub like crazy. But it's closer to '70's street freak height than it is to stock.

295's do not fit on a stock Duster. 1/2" offset and some quarter lip trimming is the only way to get them to fit. Anything else depends on the wheels hanging outside the quarters and the ride height more closely resembling a 4x4 than a car.

 

[dave225]

I need help in determining if the following wheel and tire set up will fit under my stock 73' Duster rear fender and not rub against the stock located CalTrac leaf suspension. Any help would be appreciated. My concern is that the 4.875 backspacing might be too much and cause it rub against the leaf springs. Thank you.

Wheels: Centerline 15x8.5" with a 4.875 Backspacing
Tires: P275/60r15

Why wouldn't you jack the car up and measure it to be sure?