R33 disk brake size

[Godzillaskizza]

Hi there I have a r33 gts with 4 stud small brakes, I'm going to convert to 5 stud but keep the small brakes, what size rotor would I need?

[Duncan]

If you are keeping the current calipers you need to keep the current disc as the spacing of the caliper determines the disc diameter.

Have you trial fitted the GTS brakes fit on a GTSt hub or is this forward planning? There could be differences in caliper mount spacing, backing plate and even hub shape that could cause an issue.

[blind_elk]

Why would you not fit the biggest possible brakes?

[Yeetus]

A quick Google said 297mm..

[GTSBoy]

6 hours ago, Duncan said:

If you are keeping the current calipers you need to keep the current disc as the spacing of the caliper determines the disc diameter.

This. And also, the rotor thickness is constrained by the calipers. Cannot be much thicker, if at all. Cannot be much thinner, if at all.

New rotors are....fairly cheap. Turbo calipers can still be picked up for sensible money.

Arguably, the best thing is to get R32 calipers and put them on mount spacers on 324mm discs. That's about the cheapest and easiest way to get quite large brakes that are essentially bolt on. And that's despite maintaining for years that the R32 calipers are not the best choice because they seem to be more flexy and creaky than the others. If you were prepared to put up with nasty little NA sliding calipers, these will still seem like Brembos by comparison.