The 7 inch rim will weigh less than a 8 inch rim. I had a set of 8's on the roadster ... at first and changed to 7's.

Actually ... the coupe has the more narrow rear axle. It measures 56 inches ... this way.



The roadster measures 58 inches ... measured the same way.

You will be surprised at the difference in the weight ... of different tire sizes and tire brands.
I even installed a aluminum 9 inch center section under my 32's ... to reduce unsprung weight. It helped by almost 20 pounds.



The driveshaft is aluminum too ... but painted BLACK.
I have been told quite a few times that my 32's ride better than any other 32 they have riden in ... so it is not just my imagination.
But then my 32's ride on coil springs, not coil overs or a transverse spring.