I am building up a road bike for my wife and plan using a R600 compact crankset (50/34) with a SRAM 9-speed cassette. I recently ordered Tiagra derailleurs from Nashbar to complete the drivetrain. This is the front that I ordered:
mainly because it said it was compact crank compatiple and had a multi-clamp that should work with the 31.8mm seat tube. But when I received it and opened it up it looked completely different than the picture, the clamp was for a 34.9mm tube and there were no shims or other provision to make it properly fit a smaller tube. Also, the instruction specifically list the maximum chainring difference as 15 or less, not the 16 that my (and most other?) compacts have.
I called Nashbar and talked to a tech who told me that 1)The picture on their website for that product is wrong and that the double which I need is longer slender like the one that I received. 2) They forgot to send the shims and he would send a set right out. And 3) that the one they send would in fact work fine with a 16t chainring spread.
So can anyone confirm or deny what I have been told? I don't have the rest of the parts yet to actually test it out.
1. Shimano is very conservative with their max ratings which can almost always be beated by a tooth or 2
2. Shimano came late to the compact crankset party and took the time to make a crankset that was spec'd to work with the existing Shimano derailliurs without problem. Some of the other early compact cranks worked best with a special derailleur for the 16 tooth spread.
I believe that once you have the shims that you will be good to go.