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Shimano DA chainrings?(2 posts)

Shimano DA chainrings?spinner54
Jul 12, 2001 6:21 PM
What's the deal with the "A" and "B" designations? Shimano literature says not to mix them. I use an "A 42" and an "A 53" but I bought a 39 for a specific event and I noticed it is "B 39". I put the "B 39" on with the "A 53" last night and it seems to shift just fine but I have only done a short recovery ride. Seems compatible but I'm curious about the Shimano statement regarding mixing.
You shouldn't mix them...TJeanloz
Jul 14, 2001 10:10 AM
Shimano has two ramp patterns, A and B, which theoretically shouldn't be mixed. It isn't a case where it won't work if you mix them, it just won't work as well. The ramps are designed to provide optimum shifting between rings, and it wouldn't shock me if mixing A's and B's caused slower shifts, especially under load.