Quote Originally Posted by mknight View Post
Nope, you can run with 4, and everyone in WRC except Tanak has been doing that for 3 SS now.
Unless supplementary regs amend this (need to check), FIA regulations state the following:

13.11 SPARE WHEELS
Cars may carry a maximum of two spare wheels. If stipulated in the Appendix J for the concerned group, cars must carry at least one spare wheel.