Yet Another Offset/Clearance Question

[GatorJ]

I am in the process of locating a set of Watanabe wheels for my 1970 Fairlady Z. Unless I purchase a new set (expensive!) or get very lucky, I'm going to have to get reasonably close to the optimum offset. I am looking at 15" diameter wheels in either 7" or 6.5" width. I have been using an offset wheel calculator do determine overall effects on inner clearance, etc., and have done a search. What is the maximum amount of inner clearance loss I can go with a stock suspension/brake set-up? Asked a different way, what is the maximum amount of positive offset I can go in both 6.5" and 7" widths without having a problem? My preference would be to NOT use spacers. Thanks in advance.

[Mr Camouflage]

I was just out in the garage measuring up the suspension to work out the same thing.

This is what i came up with:

Firstly forget about offset. Start with how much clearance there is between the hub mounting face and the suspension (I havent considered how much clearance there is between the chassis and the wheel on full lock though)

For the front I came up with 130mm (240Z), say minus 15 mm for tyre clearance (so your tyres dont rub on the spring perch when cornering) would give you a back spacing of 115mm.

Second work out the width of the rim. Lets say 7" = 179mm

Third, maximum offset = backspacing - (width/2)

115 - (179/2) = 25.5mm which is +25 offset.

For a 6.5 it would be +32

So, I think thats right.

However, having said all that you'd really want to get as close to 0 offset for a 6 to 7" rim.

Currently the car has 14 x 7 with 0 offset and 235 tyres