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Granny Chain Ring Compatibility(6 posts)

Granny Chain Ring CompatibilityTarzan
Sep 17, 2001 6:53 PM
How do I purchase a granny (say 28 teeth) chain ring that will be compatible with the Shimano 105 30/42/52 triple crankset? What do I look for?

Are there any performance issues if I go to even a smaller ring, say 26 teeth?

P.S. This is for loaded touring. The cogset can be either 11-32 or 11-34.
re: Granny Chain Ring Compatibilitydavet
Sep 17, 2001 7:16 PM
Sugino makes Shimano compatible small chainrings in 24, 26 and 28 tooth. Because Treks' barcon chainring shifter is friction, there should not be any issues with the 28 tooth ring. If you change to a real small chainring (24 or 26) you may want your LBS to fine tune the front der if you can't. The chain may have to be shortend slightly. If your bike had STI shifters, adjusting the front der for proper shifting would be very difficult and shifting from the small to the medium chainring would not be reliable. Not every LBS stocks the smaller than standard chanrings, but they are easy to get.
re: Granny Chain Ring CompatibilityAtombomber
Sep 17, 2001 8:26 PM
The granny ring bolt circle measures 74mm. This will allow any standard mountain granny ring to mount onto the crank. The problem you might face is that if you go too small with the granny ring, the deraileur might be too high and the chain might rub against it. If you lower it, then you run the risk of it making contact with the larger rings. 28t grannys were available before compact systems became popular, so you might have luck at well established bike shops (those that have been around for a long time).
re: Granny Chain Ring CompatibilityTarzan
Sep 18, 2001 12:08 AM
Thanks to all!! :-)
re: Granny Chain Ring CompatibilityChen2
Sep 18, 2001 7:23 AM
I think you may be asking for trouble. Shifting a Shimano triple from the 30 up to the 42 is trouble enough as it is. I would suggest you leave the triple as is and go with a 12-34 cassette and rear derailleur. That is an easy conversion and should shift well. My wife's road bike has the standard Ultegra crank set with XTR 12-34 cassette and rear derailleur, this combination shifts as well as the original group, though the ratios are awfully wide.
re: Granny Chain Ring CompatibilityKen
Sep 18, 2001 7:26 AM
I have a Cannondale T800. The bike originally came with a Coda triple crank, 30/42/52. I changed the cranks to Ultegra because the middle and big rings are ramped to help facilitate upshifting. With ramped rings I changed the 30t granny to a 26t one. The setup works fine. Going up those long steep climbs with any type of load is a lot easier with the 26t. I didn't consider the 28t granny because I figured the percentage gain over the 30t granny wasn't worth it. My rear cogset is a 12/34.