I rode with 35c Kojaks on R501 - all ok.
I have 28s on mine; but if you are going to run 32 or more then I suggest you go for 17mm or 19mm rims.
@Peter_Carter started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
I rode with 35c Kojaks on R501 - all ok.