OK guys, I know this is like jumping on a grenade, but here I go:
After speaking with Shimano on the phone regarding the use of compact chainring cranks I have been twice advised that the minimum size tooth count for a Shimano Dura-Ace front derailleur is 39 teeth. A compact style crank has 34 teeth. This is out of spec.
Because of this, Shimano does not recommend its use.
Several thoughts:
1. We warn customers about this Shimano Advisory if they purchase a compact crank from us and, at this time, recommend they stay with Shimano brand cranks when using Shimano brand front derailleurs.
2. Yes, I know yours works just fine. However, we need to have a written, quotable, tested and factory "certified" or approved protocol for this in the event of an accident or mechanical failure.
3. Yes, I acknowledge that some of Shimano's motivation for this may originate from the fact that Shimano does not currently manufacture a compact style crank.
4. Campagnolo is currently developing a compact crank for release in fall of '04 and WILL include a compact radius geometry front derailleur specifically intended for use with a reduced radius, 50/34 tooth compact style chainring.
5. I phoned FSA (one prominent manufacturer of compact style cranks) twice this morning for their input but, as of this hour, have been unable to reach them for their comments.
-submitted for your review and commentary.
Tom Demerly
The Tri Shop.com
After speaking with Shimano on the phone regarding the use of compact chainring cranks I have been twice advised that the minimum size tooth count for a Shimano Dura-Ace front derailleur is 39 teeth. A compact style crank has 34 teeth. This is out of spec.
Because of this, Shimano does not recommend its use.
Several thoughts:
1. We warn customers about this Shimano Advisory if they purchase a compact crank from us and, at this time, recommend they stay with Shimano brand cranks when using Shimano brand front derailleurs.
2. Yes, I know yours works just fine. However, we need to have a written, quotable, tested and factory "certified" or approved protocol for this in the event of an accident or mechanical failure.
3. Yes, I acknowledge that some of Shimano's motivation for this may originate from the fact that Shimano does not currently manufacture a compact style crank.
4. Campagnolo is currently developing a compact crank for release in fall of '04 and WILL include a compact radius geometry front derailleur specifically intended for use with a reduced radius, 50/34 tooth compact style chainring.
5. I phoned FSA (one prominent manufacturer of compact style cranks) twice this morning for their input but, as of this hour, have been unable to reach them for their comments.
-submitted for your review and commentary.
Tom Demerly
The Tri Shop.com