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Ok I've been reading threads and haven't found my answer. If you run a 15x10 wheel with rear disc what should you set the BS at? I know you want 5.5 BS to get the wheel to sit in the wells on a 70 with 295/50R15's without mods or interference. But since disc will move wheel out a bit due to thicker rotor cap I don't want to assume no issues. Rear will run probably an S10 conversion brake kit.
I'm sure this is not the answer you'd like, but your objective while difficult, will require a whole lot of measuring and anticipacition of potential problems. If there were an easy solution, everyone would do it. I suspect that has something to do with the desire to do it. I'd suggest setting up the brakes with standard wheels and adjust your bs (or offset) Joe P accordingly. Be patient and do it right the first time. Above all else make sure that the end product is sound and safe to enjoy. Of course another alternative is a modified rear setup for a rear disk kit and custom track width. If you were to go this route, you could choose your wheel offset.
With the oversize wheel wells on the rear of the 70-72 Cutlass the 5.5 bs wheels and 295 will probably still fit. The disc brake might be at most .25" thicker than a drum, this is not going to make much difference at all. These cars have more room out from the wheel mount surface to the inner fender lip than they do from wheel mount surface to the inner well/frame.
There is no way to provide a useful answer to this question without knowing the contour of the backside of the specific wheels you are using. Every wheel manufacturer has a different backside contour. In addition, one would need to know the exact mounting location of the caliper and the physical dimensions of the caliper. There is no "standard" design here.
These will be custom SSIII wheels so BS can be set anywhere.
And the problem is still that since the barrels are "custom", we have no idea what the backside contour will look like. The problem with SSII/III wheels in general is that they all use the same center disc. This means that the 15" rims require a larger than normal center drop to mate up with what is the center disc from a 14" wheel. The result is clearance problems for calipers if the rotor is over the stock 10.75" diameter. It's really more important to use rotors with a taller "hat" that moves the disc and caliper inboard relative to the wheel mounting surface. This is far more important than the backspace as far as caliper clearance is concerned.
A great deal of truth to Joe's comment, also the back spacing is not totally unlimited. When I fabricated mine with 4.75" offset the center section was right at the ragged edge of the dropped portion of the shell. If I had wanted less offset, I would have had to cut material from the center section or other creative measures that would ultimately sacrifice the structural integrity of the wheel. This is compounded by the additional weight of the wheel, heavy tires as well as a longer arm of leverage on the center section. You can see this in the inner view (bottom) of the image. Also, as I recall, with a 295 50 r15 my frame clearance was approximately 0.5"... Not so much! Again, I'd advise lots of measuring and preemptive planning to avoid problems. Good Luck!
[QUOTE=Funkwagon455;951887]A great deal of truth to Joe's comment, also the back spacing is not totally unlimited. When I fabricated mine with 4.75" offset the center section was right at the ragged edge of the dropped portion of the shell. If I had wanted less offset, I would have had to cut material from the center section or other creative measures that would ultimately sacrifice the structural integrity of the wheel. This is compounded by the additional weight of the wheel, heavy tires as well as a longer arm of leverage on the center section. You can see this in the inner view (bottom) of the image. Also, as I recall, with a 295 50 r15 my frame clearance was approximately 0.5"... Not so much! Again, I'd advise lots of measuring and preemptive planning to avoid problems. Good Luck!
Why are you saying 4.75" of offset. What you mean is 4.75" of back spacing is it not? Offset & backspace are not the same thing.
I recently purchased some 15" SS 11 rims that were widened to 10" many years ago. Seller claimed that he had them on numerous 1970-1972 A body Oldsmobile cars. I tried mounting them on my 1970 W-31 & they bolt up fine. There is 295 50 15s mounted on the rims. The rims have 4.5" of BS. As tested on my W-31 this wheel & tire combination won't work. The rim needs another .25" of BS to work & 5" BS would be better. The wheel well lip sits directly above the tire sidewall & will cut the tire if the car squats or weight is added in the rear & I am unwilling to add air shocks.
I will try the wheels/tires on my 73 442 & see if they work on it.
s10 pushes your wheels out 1/4", your ideal BS is 5.5", order the wheels with 5.75" BS and you'll be fine.
I've had 10" wheels 5.75"BS with 305 tire fit fine no issues, and I've had wheels with 5" BS" 295 tire fit fine, my car is lowered 2".
What I'm trying to say is with the 295/50 you got some wiggle room, not much, but if you are 1/4" off, it won't make a big difference.
I'll assume you meant 4.5" and 4.75"... Regarding air shocks, I did not want to run them either. I have Air Lift bags in my rear springs. It is a low cost alternative that does not sacrifice the ride. Plus (like air shocks). They can be individually adjusted for load or traction based on your needs.
September 7th, 2016, 06:28 PM
accordingly. Be patient and do it right the first time. Above all else make sure that the end product is sound and safe to enjoy. Of course another alternative is a modified rear setup for a rear disk kit and custom track width. If you were to go this route, you could choose your wheel offset.
Again, I'd advise lots of measuring and preemptive planning to avoid problems. Good Luck!
