# A-type and B-type Shimano chainrings...



## Pieter (Oct 17, 2005)

Could anybody please enlighten me about the differences between abovementioned two?

Vendors advise that A should be used with A and B likewise, when pairing chainrings on a double crankset.

Myself, I have paired more (apparently) divergent rings than these without hassles.


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## Dave Hickey (Jan 27, 2002)

I've mixed them for years without an issue... I've read that A and B has to do with the location of the ramps and pins to aid in shifting but I've never had a problem mixing A and B rings


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## nhluhr (Sep 9, 2010)

Dave Hickey said:


> I've read that A and B has to do with the location of the ramps and pins to aid in shifting but I've never had a problem mixing A and B rings


That's exactly what it is. It's not that it would cause a problem, but having the ramps coordinated makes shifting smoother, especially under power.


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## shinewheel (Jan 14, 2011)

what they said, it's about the ratios you desire, the A type matches a 53 with a 42 inner for better shifts, while the B type matches 52 or 53 with a 39 inner.


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## Kuma601 (Jan 22, 2004)

+1 to what Dave posted. "Optimal" used by Shimano techs is the word. In practice, I notice it to catch about 1/8 a crank revolution from the shift. Depending on your RPM at the time, it may or may not even be noticed.


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## Pieter (Oct 17, 2005)

Thanks for the responses!

I suppose any difference there would not bother me. 

I tend to be very old-skool cautious and slow with chainring shifts anyway, what with carbon chainstay and risk of chainsuck :blush2:


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