Want 275s street slicks…it will be a damn close fit. should I chance it?

[MRGTX]

Currently running 15x8, 0 offset wheels with 255/60/15. The car has an a-body width 8.75” with disk brakes so the fit may be unique.

They are pretty snug at the fender (had to slightly roll the lip to fit (likely exacerbated by the Hotchkis lowering springs and .5” lowering blocks). On the spring side, I have a bit of breathing room; about 22-24mm.

My extra wheels that the tires would go on have a +10mm offset/4.9” backspace. According to the tires n’ rims calculator, a 15x8 wheel with a 10mm offset (4.9” backspace) and 275mm tires would be the same distance from the fenders and 20mm closer to the springs.

They should fit but barely…

The Mickey Thompson tires that I’m looking at don’t come in 255 or 265 so I’m stuck with 275s.

I don’t want to mess with the fenders any more so spacers/more rolling isn’t preferable…

Would you chance it?

 

[67/6barracuda]

I got 275/60/15 on my 67 barracuda with the shackle kit.

 

[MRGTX]

I got 275/60/15 on my 67 barracuda with the shackle kit.

How much did the shackle kit move the spring?

Not sure if this is ideal for me anyway. I’m still interested in handling performance so moving the springs inboard is not preferable.

 

[toolmanmike]

Currently running 15x8, 0 offset wheels with 255/60/15. The car has an a-body width 8.75” with disk brakes so the fit may be unique.

They are pretty snug at the fender (had to slightly roll the lip to fit (likely exacerbated by the Hotchkis lowering springs and .5” lowering blocks). On the spring side, I have a bit of breathing room; about 22-24mm.

My extra wheels that the tires would go on have a +10mm offset/4.9” backspace. According to the tires n’ rims calculator, a 15x8 wheel with a 10mm offset (4.9” backspace) and 275mm tires would be the same distance from the fenders and 20mm closer to the springs.

They should fit but barely…

The Mickey Thompson tires that I’m looking at don’t come in 255 or 265 so I’m stuck with 275s.

I don’t want to mess with the fenders any more so spacers/more rolling isn’t preferable…

Would you chance it?

What car?

 

[K.O. SWINGER]

What year and model are we talking about here?

 

[doug 371]

mount the bare rim...if you have 2 inches clearance on each side go for it...bulge to buldge is about 11.5

 

[67/6barracuda]

How much did the shackle kit move the spring?

Not sure if this is ideal for me anyway. I’m still interested in handling performance so moving the springs inboard is not preferable.

Only moves it in about a 1/2” sometimes that’s all you need.

 

[72bluNblu]

Currently running 15x8, 0 offset wheels with 255/60/15. The car has an a-body width 8.75” with disk brakes so the fit may be unique.

They are pretty snug at the fender (had to slightly roll the lip to fit (likely exacerbated by the Hotchkis lowering springs and .5” lowering blocks). On the spring side, I have a bit of breathing room; about 22-24mm.

My extra wheels that the tires would go on have a +10mm offset/4.9” backspace. According to the tires n’ rims calculator, a 15x8 wheel with a 10mm offset (4.9” backspace) and 275mm tires would be the same distance from the fenders and 20mm closer to the springs.

They should fit but barely…

The Mickey Thompson tires that I’m looking at don’t come in 255 or 265 so I’m stuck with 275s.

I don’t want to mess with the fenders any more so spacers/more rolling isn’t preferable…

Would you chance it?

On your Dart Sport?

Not surprising you had to roll the quarters to fit the 255/60/15 with a lowered car and a 0 offset 15x8 with BBP disks. That'd be pretty much every Duster/Dart Sport with a BBP 8 3/4 and disks, you need about a 5" backspace with that combo not 4.5".

The extra wheels are a better fit, but if you really only have 22mm from springs to tire now and the 275's end up 20mm further in then you won't have enough spring clearance. And, the taller tire may create problems at the quarter even though they're not further out because they'll be further up into the wheel well. Since the outer wheel tub is tapered, you'll lose clearance even keeping the outer face of the wheel in the same place.

It will totally depend on the actual section widths. Like, what's the actual section width of your 255's compared to the actual section width of the 275's. The calculator I use lists the section widths at 10" for the 255 and 10.8" for the 275. But for a BFG T/A those numbers are 10.2" and 11". For these MT's Mickey Thompson 3453 Mickey Thompson ET Street S/S Tires | Summit Racing the section width is 11.1", which means they're probably not gonna fit.

How much did the shackle kit move the spring?

Not sure if this is ideal for me anyway. I’m still interested in handling performance so moving the springs inboard is not preferable.

The hanger/shackle offset kits move the springs about a 1/2" (both the DoctorDiff kit and the MP kit). It would be enough to clear your 275's for sure. I was running 295/35/18's on my Duster with a 1/2" offset kit and rolled quarters, and I'm lowered as well. I've since re-made my outer wheel tub so the outer section is vertical, but that wasn't necessary until I added disks and went to 27" tall 295/40/18's. I could have cleared them if I had a bit more backspacing too, I just didn't want to replace my wheels. They were perfect with my drums, with the disks and the taller tire I needed another 5-7mm of backspace.

And I wouldn't worry about the handling change on a 1/2" offset. I don't. With a 3" relocation it's more significant, but even then you just need slightly stiffer springs or a bigger diameter sway bar compared to using factory locations.

 

[ir3333]

yes...what vehicle, engine, cam and gear? That's a lot of tire.

 

[MRGTX]

What car?

'73 Dart sport.

On your Dart Sport?

Not surprising you had to roll the quarters to fit the 255/60/15 with a lowered car and a 0 offset 15x8 with BBP disks. That'd be pretty much every Duster/Dart Sport with a BBP 8 3/4 and disks, you need about a 5" backspace with that combo not 4.5". ...

Yep. The 4.5" backspace was preferable for the rear because they alleviate the narrower rear track to slightly. It was mostly an aesthetic choice. I made sure my spares were the 4.9" offset version knowing that if/when I used them, I would likely need the extra space at the fender, so that would take precedence.

The extra wheels are a better fit, but if you really only have 22mm from springs to tire now and the 275's end up 20mm further in then you won't have enough spring clearance. And, the taller tire may create problems at the quarter even though they're not further out because they'll be further up into the wheel well. Since the outer wheel tub is tapered, you'll lose clearance even keeping the outer face of the wheel in the same place.

It will totally depend on the actual section widths. Like, what's the actual section width of your 255's compared to the actual section width of the 275's. The calculator I use lists the section widths at 10" for the 255 and 10.8" for the 275. But for a BFG T/A those numbers are 10.2" and 11". For these MT's Mickey Thompson 3453 Mickey Thompson ET Street S/S Tires | Summit Racing the section width is 11.1", which means they're probably not gonna fit.
...

Good points all around, especially regarding the potential problems caused by the extra height. I hadn't thought to worry about that.

The hanger/shackle offset kits move the springs about a 1/2" (both the DoctorDiff kit and the MP kit). It would be enough to clear your 275's for sure. I was running 295/35/18's on my Duster with a 1/2" offset kit and rolled quarters, and I'm lowered as well. I've since re-made my outer wheel tub so the outer section is vertical, but that wasn't necessary until I added disks and went to 27" tall 295/40/18's. I could have cleared them if I had a bit more backspacing too, I just didn't want to replace my wheels. They were perfect with my drums, with the disks and the taller tire I needed another 5-7mm of backspace.

And I wouldn't worry about the handling change on a 1/2" offset. I don't. With a 3" relocation it's more significant, but even then you just need slightly stiffer springs or a bigger diameter sway bar compared to using factory locations.

This sounds like it may be the best way to go, unfortunately... I really don't like the idea of making the geometry less favorable but I'm willing to accept that I'm overestimating the effects. I'll look into this.

Thanks for all the input!

yes...what vehicle, engine, cam and gear? That's a lot of tire.

Stockish Magnum300 with 4.10s. Obviously not a huge amount of power but the 255s BFG T/As aren't enough...when I finally get around to the head/cam upgrades, the all seasons will be a joke. In the 15" tire world, there's not much in between the T/As and drag radials when it comes to upgrading traction.

 

[33IMP]

Currently running 15x8, 0 offset wheels with 255/60/15. The car has an a-body width 8.75” with disk brakes so the fit may be unique.

They are pretty snug at the fender (had to slightly roll the lip to fit (likely exacerbated by the Hotchkis lowering springs and .5” lowering blocks). On the spring side, I have a bit of breathing room; about 22-24mm.

My extra wheels that the tires would go on have a +10mm offset/4.9” backspace. According to the tires n’ rims calculator, a 15x8 wheel with a 10mm offset (4.9” backspace) and 275mm tires would be the same distance from the fenders and 20mm closer to the springs.

They should fit but barely…

The Mickey Thompson tires that I’m looking at don’t come in 255 or 265 so I’m stuck with 275s.

I don’t want to mess with the fenders any more so spacers/more rolling isn’t preferable…

Would you chance it?

What tires are you looking at? Mickey makes 255/60x15 in both e.t.street R, and e.t.street SS, both of which are worlds better than a greasy rockhard t/a. I doubt you need the 275 street radial pro.
That said, i like wheels with too much backspace, lots more than too little. Too much bs can be easily fixed, and dialed in to perfection with QUALITY wheel spacers.
I have eleven,ten, and nine second cars with long studs that use spacers. One set i made of steel, slightly different for each side, one set i made of billet aluminum, and one set of bought aluminum cause i retired and didnt have access to the machine shop any more.