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

toolmanmike said
What car?

'73 Dart sport.

72bluNblu said
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.

72bluNblu said
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.

72bluNblu said
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!

ir3333 said
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.