My 92 Z has the 245/50/R16 tires on the car... as it came from the factory... I have the chance to buy four decent rims with decent 235/55/R16 tires on them which was also stock.. but on the RS i am guessing... as i calc it, this will result in a different sidewall height... can they be one-for-one swapped or will this screw up the speedo setup?

Anyone try this yet?

 

I swapped a set on my fronts years ago that I got from a buddy who was having a new set put on and his fronts were still good. I’d have to check but I believe the overall difference between the two is so small you may not notice. It has a higher profile but narrower width so I believe overall height is close to same.

I just went and checked and it looks to be about a half inch difference. Keep in mind this is total diameter so your ride height and clearance will diminish by half that. Not much at all.

 

If you have access to the 235s, measure their height and compare it to your 245s. As posted above, if the difference is minimal, so will be the effect on your speedometer.

Something else to keep in mind is the fact that actual tire dimensions will vary slightly between various manufactures' tires, even for identically-listed sizes. IOW, if there's some doubt, measure the tire(s) in question in-person.