bgnukem wrote:Just to complicate things, I experienced terrible shifting problems with my front mech (Deore XT M750 - 9 speed) when I replaced the original Deore chainset with one of the Spa Cycles triples a few years ago.
It really wouldn't work with the 10-tooth difference between the top and middle 'rings but replacing the middle with a 2T smaller ring solved the issue. It seems some front mechs may be designed to work with a larger 'drop' from large to middle 'ring, in this case 12T not 10T!
Certainly some triple mechs I have, have a much deeper cage than others which seems to be consistent with a larger drop.
To add a data point: I have a Tiagra 10 speed (current model I think) triple front with a Spa chainset (TA rings as sold by Spa) on an old touring bike. This changes really smoothly and easily across 26/36/46 and 24/34/46, using a 9 speed chain on an 8-speed cassette. I did need to set the height very carefully. To be fair this is with a friction lever mounted on Kelly Take-Offs, but I feel no need to overshift or anything, it just goes. Some trimming needed in inner and outer ring but not a lot.
It does have a deep cage and I suspect would handle say 24/36/48 too.
(Data point on life of the rings: I replaced the 26/36 with 24/34 to change the gearing. The 36 middle was quite worn after 8000 miles. Still usable but getting near the end of its life. Others were fine as I do probably 80-90% of my riding in the middle one.)
I have a newer bike with full Tiagra triple 4703 gearing including STI levers, so same front mech. This all works excellently as well, once I had practised a bit with the upshift, and the trimming feature on these levers is very good (once you have figured it out - poorly documented). This thread supports the hope that when I need to replace the chainrings, I could fit a Spa chainset with smaller rings for venturing out of the East Anglia flatlands