Shimano compact replacement chainring

[ianc]

Apologies if this has already been raised, but a quick search threw up similar problems, but no solutions.

One of my bikes has a 105 50/34 Hollowtech chainset and an 11/23 10sp cassette. As several other posters have pointed out, this results in the need for a lot of front and rear simultaneous (nearly) shifts. The problem would be much reduced for me with a 38 inner.

So I got an FSA 38t 110 BCD inner (Shimano doesn’t do a 38) which fitted OK, but resulted in the inner ring being about one mm further inboard than the original – just enough to allow the chain to fail to engage with the inner ring on front downshifts. The difference isn’t much (eg an 8/9sp chain would probably be OK) but it’s enough that no amount of front mech adjusting will make it work.

So the simple question is: does anyone know (based on first hand experience) if some other specific brand/model of inner ring will work?

Thanks.

 

[Will1985]

Flip the chainring round - one side has slightly recessed holes.

Otherwise, some spacers from SJS should do the trick.

 

[ianc]

Thanks for the suggestion.

You are correct that the ring has recesses which are designed to receive the arms of the spider. With the ring fitted this way round (ie the correct way) the inner ring is too far from the outer. Fitting spacers would increase the separation, not reduce it.

I’ve already tried fitting it the wrong way round and it made little difference to the lateral separation - the problem remained.

I think the problem with the FSA ring is that it’s designed for a 8/9sp crank.