rear tire clearance left vs. right

[c9zx]

The full story is too long to tell, short story I'm trying to fit M/T street drag radials (255)on the car. And I have them on the car. The problem is the passenger side has about 1/4"- 5/16" less clearance than the driver's side, The passenger side rubs slightly on bumps. Is this a known problem? Is the fix to properly relocate the spring perches? I also want to ditch all the rubber insulator pieces. Eventually I will install Cal-Tracs. Car is 98% street. 462 Fe, lots of good parts, solid roller cam, 4 speed. Is there an easier fix. Any and all input will be greatly appreciated. Thanks Chuck (S) Forgot, car is 1966 Cyclone GT.

[frankenfords]

I’ve run into this problem before when trying to squeeze as much tire as possible under a car. I chalk it up to ‘stacking’ of loose production tolerances, and wear and tear that comes with age. I’ve dealt with it by loosening everything up; u-bolts, front and rear spring/shackle eyebolts. Then, use a come along or ratchet straps attached to a point or points on the frame and the axle housing to pull the axle housing the direction it needs to move to even things up. Tapping the u-bolts and other places with a hammer, while under tension, can help move things. Then, once it’s where you want it, torque everything down while still under tension. It’s worked for me, but results may vary.

[427Fastback]

Common problem but never seen it that far out before.I machined 1/8 spacers for both my Mustangs to balance things out..

[mike7570]

I ordered Cal-Tracs for my Shelby clone stocker. The Cal-Trac split mono leaf springs were wider than stock springs and caused a tire clearance issue because I had purchased rims with back spacing based on the factory width springs.

[e philpott]

I'd try loosening everything up and try to reposition Diff to spring , check the rear upper shackle mount bushings to body .

[hotrodford]

To those of us that vintage road race the old Mustangs this is not at all uncommon.  In my case, since I use lowering blocks (1 inch) I offset the locating holes.  At one time offset locating pins were available in the vintage road race community. You would only need a 1/8" offset.

[c9zx]

Thanks for the replies guys, keep them coming. Eliminating the rubber "isolator" pieces should raise the back of the car 1/2 inch. This may change the clearances a bit. I ordered the Cal Tracs this AM. it comes with a solid front spring eye bushing. This likely will restrict side to side movement of the springs sideways. By the way, everyone at Calvert Racing are great to deal with. All of them are very friendly and helpful.
Thanks, Chuck (S)

[6667fan]

I was at a cruise last night and a guy showed me his 68 XR7 rear tires not being evenly spaced. I told him it’s not uncommon. My 67 Fairlane is tighter on passenger side.
I like some of the loosening/tightening ideas above. Might get you closer to even.

[Gaugster]

Same experience here. Passenger side is a little tighter that driver's side. Rubbed some with my kids in the back seat. I did a slight roll of the inner fender lip and no problems since. I'm 204lbs so I imagine it may even out a little with only myself in the car. Cal-Tracs, mono leaf and the longer 4.5" shackles seem to be working with these 275/50/17's. This is the closest I can get to the standard 28" 275 series tire category. I focused mostly on driveshaft angles but should try resetting the rear end vs leafs one day.