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Shimano "A" vs "B" chain rings(6 posts)

Shimano "A" vs "B" chain ringsDSR
Feb 19, 2003 11:41 AM
I need to pick up some new chain rings for my new used road bike. It's got a '99 9-speed Dura Ace crankset (and general components). I'm looking at just picking up a Ultegra 39T ring and 53T ring, but have seen some described as "A" and some as "B". What does that refer to? Anyone know what I need? Thanks a bunch! S
re: Shimano "A" vs "B" chain ringsjw25
Feb 19, 2003 12:42 PM
The A and B refer to the inner ring that matches - 53A is for a 42 tooth inner, 52B and 53B are for a 39 tooth inner. It's something to do with the shifting ramps, so I'd guess that a mismatch would work, but not as well as the "proper" set.
Ultegra rimgs are nice, but I'm loving a set of Stronglight rings I got from thorusa.com - it's in the Warehouse Clearance section, under RZ 130 D. Red and blue available, for a little flash, and $31.50 for both. They're nice, with ramps and pins and machined after anodizing, so the teeth are bare alloy.
I'm not Thorsten, but I am a happy customer.
re: Shimano "A" vs "B" chain ringspmf1
Feb 19, 2003 12:57 PM
The 'A' is for a triple, the 'B' is for a double. They are different and not interchangable.
I'll have to disagree on this one...seyboro
Feb 19, 2003 5:51 PM
I have had 'mismatched' D/A chainrings on one of my bikes for a few years now. They have been shifting flawlessly.
Experience with what I've gotpmf1
Feb 20, 2003 6:01 AM
Maybe I'm wrong. Here's my experience --

My wife has a bike with a triple, and we have several doubles. The inner ring on the triple (42 in Ultegra, 39 for DA) has all kinds of ramps that are not found on the double small ring. I think they're for getting the chain from the small (30 tooth) ring to the middle 39 or 42 tooth ring. All double stuff I have says 'B', all triple stuff 'A'.

I once tried to put a 39 tooth ring from a double onto her Ultegra triple. It didn't shift up from the small ring to the middle one. Perhaps its compatable one way, but not both.

As for double combinations, any combination of 53/52 and 42/39/38 will work fine.
Got it. Thanks! (nm)DSR
Feb 19, 2003 2:00 PM