federal rsr sizing

[KaneDB]

Hi all,

I'm in the process of buying a set of federal rsr tyres for the 300zx. I've read that they come up wider than their marked width. Here's my predicament! I run a 245,40,17 tyre now (hankook) on a 8.5” wheel. The two options I have are:

235,40,17 which will come up somewhere near 245 anyway, but has a lower load rating of 90 in theory 1.2% or 8mm smaller diameter.

255,40,17 I have read is more like a 265, load rating of 94. But I am wary that this might oversize the 8.5” rim. 1.2% larger.

The car weighs something like 1600kg,so I think the 90 load limit would just be OK, but I assume the 94 would also have stronger sidewalls?

Any help would be appreciated

Cheers

[KaneDB]

Sorry for any confusion, I'm not overly worried about the small increase in rolling diameter - tyres fluctuate that much from full tread to worn out anyway.

The main thing I was worried about was going too wide the width on the 8.5 wide wheel if the RSRs came up even wider, but even federal says the 255 is ok on 8.5 - 10" wheels. I'll go for the wider option. I'll post back how I find the tyres when I get them.