I wasn't aware that SRAM now also offer a 12-28, that is good to know. I'm a big fan of that combination, and have used 3 different versions in the past couple of years. IRD and BBB both make 12-28 cassettes which have closer spacing in the lower gears in exchange for not having a 16 tooth cog:
12-13-14-15-17-19-21-23-25-28
They both shifted OK for me, but never as reliably as the Shimano 105 or Ultegra cassettes that I've used. The BBB cassette is pretty heavy because it is all individual steel cogs, the IRD is a bit lighter because it uses aluminum carriers for the larger cogs. When I started to miss not having a 16 tooth cog I then made a custom combination of parts of 3 cassettes to get:
12-13-14-15-16-18-20-22-25-28
This is the ideal gear combination IMO and I was lucky that it actually shifts pretty well.
We had been using the IRD 12-28 on the tandem with 26/39/53 chainrings, but I've had multiple problems getting smooth shifting on the tandem with this cassette and others. I've now gone for a 12-32 cassette and increased the inner chainring size to a 28. This has improved both front and rear shifting. The cassette is a Shimano XT 11-32, with the 11 and 12 tooth cogs swapped out for 12 and 13 tooth cogs from an Ultegra cassette to make it:
12-13-14-16-18-20-22-25-28-32
I'm really happy with this setup and plan to keep it for a while now.
Based on TandemGeek's recent blog postings on the matter, I've also just switched from a Dura Ace shifter with XT rear derailleur to a Campy Record 10-speed shifter and SRAM X-9 10-speed rear derailleur (without any cable pull adaptor). It seems to be working better than ever, but so far I've only used it on the stand and on a short test ride. I'm looking forward to giving it a proper workout, but it's looking really promising so far.
Last edited by Chris_W; 06-10-11 at 11:45 AM.