Moving the springs inboard & using a B body housing....

[MoparJunkie]

I bought a set of the dr diff offset springs as well about a year ago, they are sitting somewhere in my parts lol. I have a 69 1/2 dana 60 from an A12 that I found locally. It will need rebuilt and I plan on putting this in my 71 challenger to fit bigger wheels and tires on. Dr diff told me that I could fit a 15x10 5.5" BS on the rear with 28x12x15 MT street radials as long as I used his rear disc brake setup that allows for the better fitment of a 1/8" difference from other setups to allow a 5.5" bs wheel. I'd prefer to put willwoods on instead, but I'd also like to be able to fit the biggest tire under my car w/o having to do major modifications. Just curious on what others thoughts are. I know 295x50x15s fit under my uncles 68 charger, but a 28x12x15 is a bit bigger of a tire and I don't want to modify the quarters (rolling a lip or cutting the lip etc) to get the tires to fit.

[1 Wild R/T]

Hey! No girlymatics allowed.....    Welcome!!!!

[GrandpaKevin]

Hey! No girlymatics allowed.....    Welcome!!!!

Thanks.

[Blake@diyhemi.com]

I bought my Dr. Diff kit about 3 years ago and used a 67 B rear 8 3/4. Fits my 11" wide rears like a dream! No mini tubs either!


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[HP2]

I bought a set of the dr diff offset springs as well about a year ago, they are sitting somewhere in my parts lol. I have a 69 1/2 dana 60 from an A12 that I found locally. It will need rebuilt and I plan on putting this in my 71 challenger to fit bigger wheels and tires on. Dr diff told me that I could fit a 15x10 5.5" BS on the rear with 28x12x15 MT street radials as long as I used his rear disc brake setup that allows for the better fitment of a 1/8" difference from other setups to allow a 5.5" bs wheel. I'd prefer to put willwoods on instead, but I'd also like to be able to fit the biggest tire under my car w/o having to do major modifications. Just curious on what others thoughts are. I know 295x50x15s fit under my uncles 68 charger, but a 28x12x15 is a bit bigger of a tire and I don't want to modify the quarters (rolling a lip or cutting the lip etc) to get the tires to fit.

Should be no trouble. I've got 15x10 with 5" BS and 26x12x15 and have room around them. An extra inch in radius would fit fine in my set up.

Rule of thumb with rear housings, 66-67 B require 5" BS, 68-70 B require 5.5" and E body with spring relo requires 6" BS. Yes, disc brake kits can throw an additional variable into the mix so understand what they are doing if fitting the maximum width is the goal.

[Cudakiller70]

I know 295x50x15s fit under my uncles 68 charger

I have this same size on my 70 Barracuda.

[MoparJunkie]

I bought a set of the dr diff offset springs as well about a year ago, they are sitting somewhere in my parts lol. I have a 69 1/2 dana 60 from an A12 that I found locally. It will need rebuilt and I plan on putting this in my 71 challenger to fit bigger wheels and tires on. Dr diff told me that I could fit a 15x10 5.5" BS on the rear with 28x12x15 MT street radials as long as I used his rear disc brake setup that allows for the better fitment of a 1/8" difference from other setups to allow a 5.5" bs wheel. I'd prefer to put willwoods on instead, but I'd also like to be able to fit the biggest tire under my car w/o having to do major modifications. Just curious on what others thoughts are. I know 295x50x15s fit under my uncles 68 charger, but a 28x12x15 is a bit bigger of a tire and I don't want to modify the quarters (rolling a lip or cutting the lip etc) to get the tires to fit.

Should be no trouble. I've got 15x10 with 5" BS and 26x12x15 and have room around them. An extra inch in radius would fit fine in my set up.

Rule of thumb with rear housings, 66-67 B require 5" BS, 68-70 B require 5.5" and E body with spring relo requires 6" BS. Yes, disc brake kits can throw an additional variable into the mix so understand what they are doing if fitting the maximum width is the goal.

Thanks for the comments guys.
Sounds like what Dr diff recommended then should work (28x12x15 on 15x10 5.5 BS with Dr diff spring relo kit and disc brakes). The only thing I noticed when wheel shopping is that there seems to be more wheels in the 5" BS vs 5.5" BS. Overall I know I want a 15x10 just not sure if I want a classic look because the wheels are steel and I would prefer aluminum to shed some unnecessary weight from the car. There were some weld wheels I think I liked but there were some comments of people complaining the fronts were cracking on them. If I go oldschool it will either be rally or magnum wheels. Overall wish there were more wheel choices, I refuse to put anything bigger than a 15 on an ebody. Just personal preference but I don't like bigger wheels on cars unless it suites them. The smaller E bodies for example in my opinion look better with 15s but the bigger B bodies I like 17s on.  Overall I prefer that meaty tire look vs a rubberband lol.

Appreciate the comments guys, sorry for jacking the thread lol.

[GrandpaKevin]

Before you spend money on wheels and tires make sure you measure and are certain what size B body rear end you are using, it could be critical.

I installed a 1967 B body 8 3/4 in my wife's Challenger and did a quick fitment check with a pair of 28x12.50 ET Streets on 15x10 Weld wheels with 5 1/2 back spacing, it was too close to the leaf springs for my liking.
I installed Moser axles with longer wheel studs so I was able to add a 1/4" wheel spacer which gave me just enough clearance.

I have a pair of brand new custom made Torq Thrust II wheels that are 15x10 with 5.75 back spacing.

After I get her car up and running I'm going to mount a pair of 325/50-15 BFG Drag radials on the Torq Thrusts and see if they will fit with a 1/2" wheel spacer.....

[HP2]

I installed a 1967 B body 8 3/4 in my wife's Challenger and did a quick fitment check with a pair of 28x12.50 ET Streets on 15x10 Weld wheels with 5 1/2 back spacing, it was too close to the leaf springs for my liking.
I installed Moser axles with longer wheel studs so I was able to add a 1/4" wheel spacer which gave me just enough clearance.

That is a great notation to say that personal preference and tire construction may also be factors in how close/far you want to tires to sit to components. Personally, I've got not problems running a street radial tire within .25" or less of a spring and have without dire results. IMO, the radial construction is solid enough and deflection at that point minimal enough to allow clearances on the tight side. In contrast, using a bias ply drag slick with a very soft sidewall, considerable deflection, and the possibility of high speed tire growth, I would want .5" to .75" or more.

[MoparJunkie]

I installed a 1967 B body 8 3/4 in my wife's Challenger and did a quick fitment check with a pair of 28x12.50 ET Streets on 15x10 Weld wheels with 5 1/2 back spacing, it was too close to the leaf springs for my liking.
I installed Moser axles with longer wheel studs so I was able to add a 1/4" wheel spacer which gave me just enough clearance.

That is a great notation to say that personal preference and tire construction may also be factors in how close/far you want to tires to sit to components. Personally, I've got not problems running a street radial tire within .25" or less of a spring and have without dire results. IMO, the radial construction is solid enough and deflection at that point minimal enough to allow clearances on the tight side. In contrast, using a bias ply drag slick with a very soft sidewall, considerable deflection, and the possibility of high speed tire growth, I would want .5" to .75" or more.

Good point, I'm considering testing a 295x50x15 first then perhaps the bigger 28x12x15 afterwards. I can always do a big burnout or 2 if I wanted different tires faster hahaha. I will be running drag radials or possibly slicks for some fun at the track, so I need to keep that in mind. I don't want to run wheel spacers at all. I'm just looking to fit the max tire/wheel under the rear with just doing what seems to be the pretty simple B body rear end to an E body car. I have no desire to hack up the rear end, tub or anything like that just in case I want to go back to a more stock look. Plus there are enough full drag older muscle cars, and I personally would rather keep more true to the original structure. Minus the US Tools stiffening kit, which wiil be added.