Originally Posted by
Mad Honk
I have replace a lot of pulleys and the one thing to remember is the Campy bolts are 5mm and all of the newer Shimano are 6mm. I buy the sealed units from chasertech and ask for special reducer to 5mm. Be sure to specify ten tooth wheels when ordering, but they work quite nicely. Smiles, MH
Many of the "shimano" aftermarket pullies have a 6mm hole with the 5mm reducer, but all of Shimano's pulleys from the past 30 years use 5mm bolts for the pulleys.
I tend to save all the durable pulleys from damaged Suntour derailers for use on Simplex or Huret derailers which all have 6mm bolts.
Shimano did apparently make at least one derailer with 6mm bolts back in the 70's or so, at least I do have such a pair of shimano pulleys here (with 6mm bushings in them that couldn't have come from Suntour pulleys). These are old-looking parts so guessing lower-end 1970's.
PCB is exactly right about rigid pulleys shifting best on friction setups using pre-Hyperglide era freewheels. Friction shifting is noticeably easier and more precise with the rigid pulleys (versus floating pulleys) I've found, even when using Uniglide freewheel with modern chain.