Has anyone got experience of using one of these? It's an Avid Microdaptor. The purpose is to reduced the 74mm BCD down to a 58mm BCD in order to fit smaller inner rings. Smallest 74mm inner is 24tooth. I have a 20 tooth inner fitted to my triple.
Using the adaptor increases the normal chainring gap by 6mm, how does this affect the shifting? Does the adaptor act as a guide as the chain drops and rises?
if your present 74mm BCD ring is fitted with spacers, and you can fit the adapter without the spacers, the chainring spacing will still be more than normal but it will probably work without a hitch; the spider looks to have a bevel on it to act as a chain guide. I don't expect the shift to be super slick mind.
If your present inner ring fits directly without spacers then I'm not sure a +6mm gap is going to work so well, but I don't know that for sure. There won't actually be a 6mm gap anywhere; but this is just as well, some modern chains can fall into a gap that size and get jammed.
I'm not sure, but I think if you have spacers for the small ring, and you use these on the 58bcd, and the spider in place of the spacers as it were, you may well be able to make a quad setup....
They've been out of production for a while, like the Limbo Spider and Mountain Tamer Quad. The adaptor replaces the small chainring's spacers, as Brucey writes.
You may need a longer BB axle for your frame to accomodate the extra gap between inner ring and middle ring,you're front mech may not accomodate the extra throw needed. You may also encounter problems if you're using STI's
