275/60/15 on rear of Duster/Dart

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Builderguy

Builderguy

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The rear end is not in the car right now, so to save a bunch of measuring, is anyone running 275/60/15 on the rear of their car. Want to make sure there is enough clearance (mostly width as the tire is around 10" wide). I am running stock, 15 X 6.5 Rallye wheels, which I think are 5.5 back space, on a 1974 Dart Sport. Thanks in advance. Ray
 
A 275 is pretty big on a 6.5" wide wheel- you really should have them on an 8-9" rim. A 6.5 is going to pinch that tire down to the point where the tread and sidewall are going to be pretty bowed, which is going to affect wear and bead seating...
And double check that backspacing, sounds a little much to me for a stock rim. Have your springs been relocated or tubs/minitubs been installed? Where is your ride height?
I'm pretty sure you can fit a 275 into a Duster/D.S. rear wheel well but at that size you're going to have to be pretty exact with the sizing and backspacing of the wheel for your particular car- production variances are going to throw things off- what worked for someone else may not quite fit yours when things get that tight.
 
That tire needs a 8 inch rim minimum,that size will fit in a duster wheel well your back space might need to be 4.5. Not 100% on that due to the different bolt pattern axles 5x4.5
 
The other problem, I found with that size is that it’s hard to find a balance between front and rear tire size, for example 205 70 14 and a 255 60 15 look good and a 195 75 14 and a 245 60 15 look good too. But I always had a issue finding a decent front tire with the the rear 275 60 15, it always looked like a hot wheel car on my barracuda.
 
Builderguy said:
The rear end is not in the car right now, so to save a bunch of measuring, is anyone running 275/60/15 on the rear of their car. Want to make sure there is enough clearance (mostly width as the tire is around 10" wide). I am running stock, 15 X 6.5 Rallye wheels, which I think are 5.5 back space, on a 1974 Dart Sport. Thanks in advance. Ray
Click to expand...

You're going to need 15x8's to run the 275 at the least. I have 255's on an 8" wheel with the factory 8.25 rearend. Really thought I wanted a 275 but not now. I don't like the jacked-up rear look and enjoy the smaller tire's performance with my 3.21's. Cruising with lower rpm in 4th gear would be nice but I have a puny low compression 340 and need the small tire more than the tall one. I decided I would get a GV in order to affect my cruise rpm's rather than using tire diameter. Those are my limitations and reasoning. You'll have yours.
What are you trying to make this tire work with as far as gear ratio (trans/rearend)? your 1st gear ratio is an important factor. If the rear is an OEM 8.25 you will need to run a spring relocation and spacers. With an a-body 8.75 and bbp axles, you will have better fitment but you still need to keep an eye on all the potential rub areas.
Check out this informative post on axle and housing widths.
What my plan WAS: swap narrow 8.25 for wider 8.75, ditch the spacers, +2" leaf springs, 275's, re-gear to 3.55's. Gains low end performance but then I'm back to revving it out on the highway. Run 275's and 3.21's and suffer in starting gear and be able to drive comfortably on the interstate?
It's all about choices and a 275 can and is done. I know that member OMM uses 275's a lot.
 
What rear end are you using? That makes some difference. The stock A body 8-1/4 is a bit wider than the stock A body 8-3/4. On my 74 Duster, I run a stock width A body 8-3/4 with drum brakes and super stock (002-003) springs. I have ran 15x8 w. 4.5" back space, 15x8.5 w. 4-7/8 back space and 15x10 w.4-7/8 back space, all with 275-60-15 s. The 15x10s look the best, but on my car, they would require a bit of fender lip trimming if you were street driving with fat chick's in the back.

Cley
15x10s
FB_IMG_1757419857621.jpg

15x8.5s
20230524_065339.jpg

15x8s
20250523_155239.jpg
 
Builderguy said:
The rear end is not in the car right now, so to save a bunch of measuring, is anyone running 275/60/15 on the rear of their car. Want to make sure there is enough clearance (mostly width as the tire is around 10" wide). I am running stock, 15 X 6.5 Rallye wheels, which I think are 5.5 back space, on a 1974 Dart Sport. Thanks in advance. Ray
Click to expand...
I have installed 275/60/15 on my 69 Dart with 15x8, (relocated springs) but I do not recall the backspace. There is 1/4" max (!) between the wheel wheel trim molding and the sidewall. 255/60/15 are no problem but your sacrificing, "the look" your after. 275/60/15"s make the car look "all business"...
 

I have 275 60 15 on a 15x8 with 4" BS on my 71 Demon. I do have SS springs in stock location on the 8 3/4
 
Clelan said:
What rear end are you using? That makes some difference. The stock A body 8-1/4 is a bit wider than the stock A body 8-3/4.
Click to expand...

This is not at all true. The factory 8.25 is narrower than an A-body 8 3/4. That's even true comparing the BBP 8.25 to the SBP 8 3/4. If you add BBP axles to the 8 3/4 it's even more dramatic.

You can take a look at the measurements here An accurate 8 3/4" rear axle width list

But an 8.25 is only 56 3/4" wide WMS-WMS, where a SBP A-body 8 3/4 is 57-1/8" and one with BBP axles is 57 13/16".

For the OP, you absolutely need a 15x8" wheel for a 275/60/15. That size tire will fit on most Duster/Demon/Dart Sport cars, but it is a tight fit and some cars might need quarter lip trimming/rolling even if the tires are located properly. Either way, a 275/60/15 should not be used on a 15x6.5" wheel.
 
Update: My mistake, the wheels are 15 x 6 1/2 but I was wrong on the backspace. It measured 4 3/8" not 5 1/2" like I thought. The older I get the more I slip !!! Anyway, thanks to all who responded. Below is what I intend to purchase.

thumbnail_IMG_6130.jpg
thumbnail_IMG_6131.jpg


I will NOT be running the 275/65/15 as they are just too big for my 6 1/2 rims as the "approved" wheel width is 7 1/2 to 9 1/2.

I will now be running 255/60/15 which is an inch shorter and .8 inch narrower. The "approved" wheel width is now 7-9. My 6 1/2 width will have to be close enough.

On the front I will be using 215/65/15 which are just about 26" tall and should clear the fender lip and not hit when going lock to lock. These have an "approved" wheel of 6- 7 1/2.

I am buying these tomorrow unless someone here has information that would make this purchase a really bad idea.

Thanks again
Ray

Nice car you have there, Clelan
 
I was running 275/60-15 on my 68. I had to trim the sheetmetal, which I wish I hadn't done. It's been so long also, but I had bought the axle assembly from someone and I think it was from a late 60's B body, but the wheels must have had more backspacing. I think they were 7" wide wheels, so the tires were probably pinched. But they were on there.
I have 255 now with much less compromise and I think looks just as good.
 
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ir3333 said:
that is a big tire. what gears are you running and do you have enough torque to spin them?
Click to expand...
The gear in it is a 2.94 Will there be enough torque, IDK, but fuel economy will be great!
That 27" tire along with the above gear ratio, at 65MPH, will only be turning 2377 RPM's

I could swing for a different gear, but this car is for sale as soon as it is completed, and if I keep changing things, it will never get completed. LOL
 
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ir3333 said:
that is a big tire. what gears are you running and do you have enough torque to spin them?
Click to expand...
BFG T/A's will still spin with a half dead 318 and 2.76's.

RogerRamRod said:
I was running 275/60-15 on my 68. I had to trim the sheetmetal, which I wish I hadn't done. It's been so long also, but I had bought the axle assembly from someone and I think it was from a late 60's B body, but the wheels must have had more backspacing. I think they were 7" wide wheels, so the tires were probably pinched. But they were on there.
I have 255 now with much less compromise and I think looks just as good.
Click to expand...

Your '68 Dart Sport/Demon/Duster?

Sorry, but there's an extra inch in the outer wheelhouse of the Dart Sport/Demon/Duster and 67-69 Barracuda's compare to a 67-76 Dart. It's not an equal comparison, 275's will fit on the Demon/Duster/Dart Sport without doing anything special on most of those cars.
 
72bluNblu said:
BFG T/A's will still spin with a half dead 318 and 2.76's.



Your '68 Dart Sport/Demon/Duster?

Sorry, but there's an extra inch in the outer wheelhouse of the Dart Sport/Demon/Duster and 67-69 Barracuda's compare to a 67-76 Dart. It's not an equal comparison, 275's will fit on the Demon/Duster/Dart Sport without doing anything special on most of those cars.
Click to expand...
68 Dart hardtop in Avatar photo. 275s on it in photo.
 
RogerRamRod said:
68 Dart hardtop in Avatar photo. 275s on it in photo.
Click to expand...

Right, and you had to cut the crap out of the quarter lip. Which is not at all necessary on a Duster/Demon/Dart Sport, because there's an extra inch in the wheel tub compared to a Dart. Have both, measured both, have had 275's on the Duster and not on the Dart because they don't fit with the stock spring locations and no cutting.

On a Dart (hardtop), there's usually ~ 11" to 11 1/8" from the spring to the quarter lip if nothing is cut (depending on the car). A 275/60/15 BFG T/A has a section width of 11". So, that doesn't work. Most quarters lips are ~1", but only about 1/2" before you get into the spot welds for the quarter panel and wheel tub. On a Duster/Demon/Dart Sport, there's ~12 from spring to quarter with nothing trimmed and everything in the stock locations. That works with a 275, you can run 3/8" to the springs and 5/8" to the quarter and that should work on most cars. Some cars may need some light rolling of the quarter lip depending on body tolerances and ride height. But with the right backspace not much is required, if anything.
 
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Yeah, ok, I didn’t see the sport qualifier in the original post, but since I did mention I was talking about a 68, the OP would also know I wasn’t talking about the same car either.
 
RogerRamRod said:
Yeah, ok, I didn’t see the sport qualifier in the original post, but since I did mention I was talking about a 68, the OP would also know I wasn’t talking about the same car either.
Click to expand...

Lots of assumptions there.

Every time someone starts one of these threads, somebody with the wrong make/model car chimes in and says something that isn't relevant for the OP. Some people just don't know, that's fine. But the OP may not know that his car and your car are different with regard to tire fit, and that's why I corrected you.

You're the one that got defensive. If you don't like being corrected, don't give bad information.
 
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