Does anyone know what size chainring spacers I need to install the inner chainring on the Powercranks (on a Shimano 9sp)? I bought the PC’s with the triple a while back, but my initial search for the correct spacers brought blank stares from the LBS. I’ve found another shop that has spacers in many different thicknesses ranging from 2mm to 5mm in small increments (0.2 - 0.5mm increments). Rather than just trial-and-error’ing it, I was hoping that someone else here is running a PC triple and has figured this one out already. The website and instructions only say to use spacers of approximately 3/16 in.
One way I was thinking of figuring it out is to use a pair of calipers to measure the thickness of the crankarm spider where the medium and large rings mount. Since they mount on opposites sides using the same hole I’m thinking that this thickness plus the thickness of the middle chainring itself should be the thickness required to offset the small ring from the middle one. Would this work? Advice would be greatly appreciated. I think I’m fairly well adapted to the PC’s now and ready to do some climbing on 'em.