1965CS wrote:

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Don' know if it helps but I believe the track width actually increased slightly, but the amount would depend on the offset of the rims. Also, I think the original size wheels were 6" wide so 8" with the same offset would widen the track a bit too.

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But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?

4SPEED427 wrote:

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I don't know if you've seen Mark's thread on the 65 and up B body conversion but there may be some info in it to help you.

Corvette rotors for big disc cars. - Canadian Poncho (activeboard.com)

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Now I did, thanks! However it brings more questions:) So his setup makes that track width value higher, which kinda eliminates possibility to have 15x8s with roughly 4 inches BS on the back. Is 15x7 the widest option for after disk brake conversion?

Oleg, I have Wheel Vintiques Series 62's 15x7 4.25" BS front, 15x8 4.25" BS rears on the 65 Laurentian. 

Went with a 69-70 single piston disc conversion on the 65.  Akerman fix as well on the 65,(67 and up Center link, Pitman, Tie rods and idler ).

Using C3 Rotors with 69 drum brake hubs. Track increase of about 1/8" each side. A 15x8 with 4.25" BS would have fit no problem up front. Chose a 7 and 8" wheel for the offset look. The 8" fits under the wheel lip on the back, but not a ton of room left.

4.25" backspace is what you want. Maybe 4" tight on the back depending on the tire section width, but I don't think any less than 4.

Neilvermilion wrote:

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But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?

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 Found the specs on my set;  

15 x 7" Bolt Circle: 5-4.75"  Back Spacing: 3.75"

15 x 8" Bolt Circle: 5-4.75"  Back Spacing: 4.5"

A 15x8" wheel with 4.5" Backspace should readily work with a rear disc conversion. Any less and you are probably into the WW lip. The rotor hat thickness on a conversion isn't likely to be over 7/16 thick.

I say this with the thinking being that I have 4.25" backspacing on a 8" wheel with a 245/60/15, and there is still a wee bit of clearance. And remember, a drum is near a good +3/16 thick on the axle anyway, so you still have that in the equation.

So keep your tread width reasonable,  add a 1/4 backspace, and then take it away with the hat thickness.

I'd like to see you take a backspace measure on those slotted wheels. 10CM past the bodyline is confusing to me. Has to be a smallish backspace on a 8" wide Wheel.

What rear disc brake setup are you planning to run Olaf?

Im about half an 1/2 inch Wider face to face