Back spacing and tire sizes

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Red63440

Red63440

Olddawg
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68 Barracuda Fastback with an 8 1/4" rear end, stock spring locations. I would like to run 15" Torque Thrust rims and have the car sit at stock ride height with the tires inside the fender wells.
Not interested in having the car jacked up in the rear, all bolt patterns are 5 x 4 1/2". What could I run as far as back spacing and tire size, front end is off a 74 dart with disk brakes.
 
Rear: 245/60/15 with 15x7 rim with 4.25" backspacing

Front 215/60/15 with 15x7 rim with 4.25" backspacing. Many can fit 225/60/15 with same rim combo. I did. But will depend on alignment specs, suspension condition, prior fender repair....
 
autoxcuda said:
Rear: 245/60/15 with 15x7 rim with 4.25" backspacing

Front 215/60/15 with 15x7 rim with 4.25" backspacing. Many can fit 225/60/15 with same rim combo. I did. But will depend on alignment specs, suspension condition, prior fender repair....
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Body is straight and suspension is freshly rebuilt, just a car for cruising.......thanks for the info.
 
Red63440 said:
Do you run 4.25 back spacing on the rear or 4.50? Can you run 3.75 in the front?
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In rear with small bolt axles redrilled to large bolt, I’ve run:

235/60/15 with 15x7 4.25” backspacing
225/60/15 with 15x7 4.25” backspacing

245/50/15 with 15x8 4.50” backspacing

* if you’re running aftermarket large bolt rear axles, 15x7 I’d run 4.25 backspace rims.

In the front with large bolt 73-76 disc conversion I’ve run:

225/60/15 with 15x7 4.25” backspacing -close
245/50/15 with 15x8 4.50” backspacing - very very close

* I would never run 3.75” backspace in front. 4.25” backing or 4.5” in the front.
 
Last edited:
autoxcuda said:
In rear with small bolt axles redrilled to large bolt, I’ve run:

235/60/15 with 15x7 4.25” backspacing
225/60/15 with 15x7 4.25” backspacing

245/50/15 with 15x8 4.50” backspacing

* if you’re running aftermarket large bolt rear axles, 15x7 I’d run 4.25 backspace rims.

In the front with large bolt 73-76 disc conversion I’ve run:

225/60/15 with 15x7 4.25” backspacing -close
245/50/15 with 15x8 4.50” backspacing - very very close

* I would never run 3.75” backspace in front. 4.25” backing or 4.5” in the front.
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I’m running a 74’ 8 1/4” year end.
 
Red63440 said:
I’m running a 74’ 8 1/4” year end.
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I’m pretty sure they have the thicker axle flange. Like an aftermarket 8 3/4 conversions.

What rear tire size do you want to run?
 
autoxcuda said:
I’m pretty sure they have the thicker axle flange. Like an aftermarket 8 3/4 conversions.

What rear tire size do you want to run?
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I want it to look good but I don’t want any problems with it. 245 -70-15 or 265-70-15 if I can run them without have a problem with clearance.
 
Red63440 said:
I want it to look good but I don’t want any problems with it. 245 -70-15 or 265-70-15 if I can run them without have a problem with clearance.
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Those 70 series have huge sidewalls. And quite a bit a bulge. You could go 245/70/15 4.25” backspace 15x7. Or 15x7 with 4.5” backspace if off shelf. Then thin spacers as needed.
 
autoxcuda said:
Those 70 series have huge sidewalls. And quite a bit a bulge. You could go 245/70/15 4.25” backspace 15x7. Or 15x7 with 4.5” backspace if off shelf. Then thin spacers as needed.
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235/60/15 on the rear with 7” width rims.
225/60/15 on the from with 7” width rims.
 
Red63440 said:
I am going to buy a set of Rocket Fuel wheels in 15 x 7 with a 4.25 backspace and a 6+ offset, they should work fine.
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Yes.

Be aware of the clearance between bottom of front fender lip and tire when turning. Especial backing out of driveway with turning.
 
I recently bought a set of these that I'll be using on my '68. They look a lot like the old Cragar G/T wheels I had on my Road Runner back in the day, which are my favorites. I'm still trying to find a set of those.
I haven't finished the mechanical work to change from BBP yet, so I can't tell you how well they fit, but I think they'll be okay with 215/60-15 tires. I think one of the keys is to keep overall tire diameter a bit under 26 inches.
The Rocket Wheels look more like the Torq Thrusts than the Cragars, but I wanted to put out another option for you to look at.
Cragar 610G571242: 610G S/S RWD Gray Wheel Size: 15" x 7" | JEGS
 
S'cuder said:
I recently bought a set of these that I'll be using on my '68. They look a lot like the old Cragar G/T wheels I had on my Road Runner back in the day, which are my favorites. I'm still trying to find a set of those.
I haven't finished the mechanical work to change from BBP yet, so I can't tell you how well they fit, but I think they'll be okay with 215/60-15 tires. I think one of the keys is to keep overall tire diameter a bit under 26 inches.
The Rocket Wheels look more like the Torq Thrusts than the Cragars, but I wanted to put out another option for you to look at.
Cragar 610G571242: 610G S/S RWD Gray Wheel Size: 15" x 7" | JEGS
Click to expand...

I saw those but after comparing the gray painted wheels and the polished/chrome wheels I chose to go with the unpainted wheels. There isn’t a lot of chrome on most of the A bodies so what little you can give them is a plus. The back space on both the front and rear is 4.25 so I should be ok. Both my front end and rear ended are from a 74 Dart, the build has sort has turned out very well so far although all the builds I have done were hands on up until this one. The car is in Montana and I am in New York State, long story. I wish you well with your build and thanks for the info!
 
IMO any backspacing from 3 7/8th"- 4 1/4" is fine with 7" wide rims . Some aftermarket wheelmakers (Weld) do not offer a 7" rim with a 4" backspace . Therefore , a 7" rim with 4 1/2" backspace is needed and shims if necessary .
 
383Scampman said:
IMO any backspacing from 3 7/8th"- 4 1/4" is fine with 7" wide rims . Some aftermarket wheelmakers (Weld) do not offer a 7" rim with a 4" backspace . Therefore , a 7" rim with 4 1/2" backspace is needed and shims if necessary .
Click to expand...

Then I should be good to go, thanks for the info!
 
383Scampman said:
IMO any backspacing from 3 7/8th"- 4 1/4" is fine with 7" wide rims . Some aftermarket wheelmakers (Weld) do not offer a 7" rim with a 4" backspace . Therefore , a 7" rim with 4 1/2" backspace is needed and shims if necessary .
Click to expand...

American Racing Wheels , ie "Torque Thrust" don't offer 4", 4.125 or 4.50 back spacing on their 7" wide rims. What they do offer is 3.76 which sort of puts an end to using them. Rocket and Vision do offer a 4.250 back space in their 7" wide rims. This is just a FYI for anyone hoping to run the Torque Thrust....
 
Mine is a 69 with sbp 8 3/4 rear, ssbc disc conversion on front

I have 15x6 3 3/8 backspace on front with 195-60 15. Could have done 205 probably.

I have 15x8 4 1/4 bs on rear with 235-60 15. My car sits high in back, have lot of room. Maybe could have done 245

6F620A9B-5760-496B-85C1-FE2354427317.jpeg
 
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