Went about making a jig from a 16" long piece of angle and a 12" piece of 1/4" allthread... dilled some lugbolt holes at one end to mount, and rotated the wheel (axle on jackstands) to determine the largest circumference without hitting... bounced the car at the tight spots just to check interferance under leaf spring compression.

Drilled hole at outter end of angle for the allthread to check width interference based on backspacing of 4" American Racing 8"x16" wheels.

I can do a total diameter of 29" and a maximum section width of 9", without skirts of course. This should make 235/65R16's an easy fit.  I'm bettin 245's would fit as well, if slightly re-route the exhaust pipe closer to the frame. An inch deeper offset would be about all any 245's would take before hitting the inner-rear fender well.

So, I'm off to buy/mount one side to confirm my findings.

I have a pair of those Aerostar coils for the front, but chickend out installing them when I saw how short they were (uncompressed) compared to the uncompressed stock units... like almost three inches.  I knew it was to lower the front, by about 1" - 1-1/2", and the spring rate is suppose to be stiffer, but the visual contrast was more than I had for experimenting at that time.  Next time I tear down the front, or get bored with the billizon other projects going on, I may put them in just to see.

Cheers... Brian

Cylinder Index = 84

Current Experiment = `57 Tbird, Grand Rapids, Michigan

I notice you have torque thrust wheels on your bird. It looks great.

Wondering what size they are and did you need a special offset to get them to fit?

I have been running American Racing Torque Thrust D's on my 57 Bird. These the standard 15X7's that Summit sells. They come with a 3.75 backspacing and -6.00 offset.



http://www.summitracing.com/parts/ARE-1055765/



The tires are Michelin 225/60 R15 Pilot Exalto. The fronts clear the ball joint and only rub on a near-lock tight turn over a bump (driveway). The rears will rub the outside inner fender well on a hard bounce or with added weight in the trunk or a hefty passenger. I carefully trimmed the inner lip of the fender well around the inside opening without weakening the welded seam and smoothed it out. Still not happy with it and worry about flexing the rear quarter panels. I added KYB gas-adjust shocks and a 1 inch rear sway bar that helped the side-to-side sway a lot. I am rethinking my wheels now, but custom backspace/offset wheels are costly.

57 Black Tbird 312/auto

If you prefer the salt flat look, Summit has Cragars (two piece) with the same size/offset for a lot less $$.



http://www.summitracing.com/parts/CRR-391G5712/



EDIT: My mistake... 15x7 Cragar 391G is 3.5" backspace, -13 offset, about 1/4" less (further out) than the smallest backspace AR Salt Flat or TTD. Dunno if these will fit.

Thanks Skygazer,



I like the Cragars but bought the American's and have them mounted. Using 225 60 15 Michelin Pilot Xaltos which are now discontinued. The 15 inch tire market is drying up.

57 Black Tbird 312/auto