[Sandwich]

hey gang, curious as to whether shoulders on chainring spacers do anything other than center the spacer on the bolt.

I have an old chainset that I'm trying to install a smaller chainring on. turns out FSA runs weird spacers and the new chainring doesn't use those spacers- I have to find even weirder spacers. In the meantime, I'm running normal spacers, but they do not have anything to center the spacer the way the old ones do. Ideally I don't want to modify the new one as the old ones are NLA. Both of the older chainrings will allow the shoulder to slide into the hole, new one will only pass the bolt.

 

[6thElement]

Are those shoulders "pinning" the chainring in alignment to the crank? Using other spacers I think you would just need to ensure the crankbolt nut is wide enough to secure the ring and the crankarm securely. If both of those are different ID holes, then GL!

 

[Sandwich]

Are those shoulders "pinning" the chainring in alignment to the crank? Using other spacers I think you would just need to ensure the crankbolt nut is wide enough to secure the ring and the crankarm securely. If both of those are different ID holes, then GL!

Yeah, so it used to be that the bolt was 8mm and the hole was 10mm. The spacers have shoulders on either size, aligning both the rings and the bolts.
The new setup has an 8mm hole in the small Ring and a 10mm on the big one.
I’ve purchased 3.5mm spacers (about the same as original 3.46mm) but they are 8mm hole, 12mm outside with no shoulders. So, I guess the inner ring is aligned but the outer can move back and forth 1mm? I would think it would, at worst, become locked in the forward or backward position.

It seems to work, but poorly. Front shifting is worse than it was, but I switched same-make crankarms and didn’t re-adjust, so it might just be slightly off in setup. It’s an FSA crank after all so I don’t expect Shimano level shifting.