For two years now, I've been successfully running a triple crank with
50-40-28 Specialites TA chainrings. I recently purchased a new 38 tooth TA
ring for the middle (gearing down a bit for a tour) and noticed a difference
from the 40 tooth I purchased 2 years ago. On the newer 38t ring, the teeth
are tapered on only one side (the outside), and are flush with the rest of
the ring on the inside. The 40 tooth is tapered symmetrically, from both
sides. The problem this is causing is that the inner plates of the chain
are catching on the top of each tooth while in the bottom three sprockets,
rendering these combinations noisy and, in the case of the bottom two,
unuseable (I realize that middle-small is a 'not-allowed' combination, but
it worked and used it occasionally). This didn't occur at all with the 40
tooth (even in the bottom sprocket) and identical chainline (115 BB, 45mm
chainline). Just by looking at it, I'm sure I wouldn't have this issue were
the teeth machined on both sides. A quick survey of every chainring I own -
big, middle, and granny - revealed that this is the only ring with teeth not
tapered from both sides. Is this a bum ring or did TA switch to a lousy
design? Should I get out my Dremel tool?
Thanks,
Kyle