Bicycle Mechanics - Outer chainring - OK to use double on triple?

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ehsiung
04-11-08, 07:56 AM
I'm replacing some worn-out drivetrain components on my Jamis Aurora, specifically the chainrings (52/42/30), chain and cassette (11-32). So I go to the LBS to get 52t and 42t chainrings (I rarely use the 30t so I'm leaving it alone). They have the chainrings but the outer is a Shimano Ultegra 52t/130mm and the packaging says it is for a double. The LBS guys say it should work fine but I thought I'd double-check with the collective.
So, does anybody know if outer chainrings for doubles are different from outer chainrings for triples? Are the ramps and pins different? Will I have any problems with installation or shifting if I use the double?
I bought the 52t so I'll try it this weekend unless anybody says this won't work. Any comments or experiences are appreciated.
HillRider
04-11-08, 09:08 AM
Shimano makes two different 52T rings, one intended to mate with a 42T middle ring (triple) and the other with a 39T inner ring (double). Theoretically they are specific. However, everything I've read and seen says the difference is so minor as to be insignificant.
capwater
04-11-08, 09:25 AM
A type vs. B type. It will work fine, though Shimano claims they need to be different for proper shifting.
Mr. Underbridge
04-11-08, 09:41 AM
A type vs. B type. It will work fine, though Shimano claims they need to be different for proper shifting.
Yup. I swapped an an A and a B, and the shift is a little crunchier, but it works.
At the same time, though - if you're paying full retail, you should get what you pay for. I got a new mismatched ring for $15 that Harris ends up with a ton of them from doing singlespeed conversions, but with a good deal I didn't mind. I'm also running Tiagra, so the FD shift was never silky smooth in the first place. If I was paying full price for a higher end group (like Ultegra), though, I'd expect it to work as designed.
ehsiung
04-11-08, 12:42 PM
Mr. Underbridge, I understand the sentiment about expectations for higher-end components but this chainring was a pretty good deal (I'm a regular at this LBS) so I don't mind experimenting a bit. I'm running a Tiagra FD right now so I don't expect things to be buttery smooth, just as long there's an improvement over the current shifting with a worn chainring.
Thanks for the comments and info everybody, much appreciated!
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