I believe Eurocharged has tried 62mm in the past. It would destroy the integrity of the pulley and cause a certain premature failure. Stack pulleys as it is not hard. A bit costly with the lower pulley needed, of course $90. to turn the stock is a break. I am very pleased with my 178/70 combo. took some trial and error but now I can pass what I did along, same as Jim. He and Rod are rhe ones who got me to not try the 178/65. Too much by far. Good luck to all!