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:
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.
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.
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.
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.
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.
Tom, if you can get 56-42 front chainring combo to work (14 tooth differential), why not 50-34 (16 tooth differential). Sounds lilke Shimano is trying to inhibit consumers from going to after market products given that it has no product line in this niche.
Are there any real differences between front derailleurs? couldn’t I just mount a Campy front derailleur onto a tri bike with bar end shifters? I mean this mostly in the context of friction shifting, not indexed shifting.
For that matter is there any reason I couldn’t use a Shimano 10 speed crank with my Campy setup?
I’m not sure what your point is. Does it matter if Shimano acknowledges that it will work? The fact that it does work is really all that matters. I’m not sure why anyone would be upset over the Shimano company line.
It is easier to get the Shimano approved proximity of 2mm from chainring to front derailleur cage with a larger chainring than a smaller one.
The small 34 tooth is so “low” on the bike the front derailleur does not even come close to matching the radius and the front derailleur mount on some frames (if it is braze-on) may not adjust low enough.
This is why Campagnolo is developing a compact specific front derailleur for their compact crank.
I think that people realize that this is marketing crap from Shimano. It’s yet another warning label whose violation means less money for Shimano. I’m sure that a front derailleur specifically designed for compact cranks would work better, but using their current model won’t kill you.
I’ve got an idea, why don’t they change their bottom bracket design again. It’s been what, 6 months?? They must be getting a little antsy.
Don’t know what this is about. You say Dura Ace front derailleur? I’ve got an Ultegra front derailleur with Dura Ace STI and rear derailleur with Stronglight compacts and everything shifts 100%.
Exactly, it all depends on if you need it or not. Sure, a non-compact drive bike may shift perfectly, but who needs that when you are pushing it up the hill and are being passed by moderately shifting compact drive bikes?
quote: It is easier to get the Shimano approved proximity of 2mm from chainring to front derailleur cage with a larger chainring than a smaller one.
does this mean that a crank with 52-36 rings will work better with a regular ShimaNO derailleur (or Campy, for that matter)? if I ever got a compact crank, I’d get a 52-36. I need the high end for steep descents (climb like feather = descend like feather). and I’d still get one gear lower than with a 39, ie with an 11-23, I’d have the equivalent of a 39-25.
What is your risk? The only downside I see is that it might not shift well. It is not like they are going to fall and break their coconut. And if it doesn’t shift well, they’re going to get online and tell the world that Tom D sold them a bike that doesn’t shift, even though Shimano told him it wouldn’t shift. Then they’re going to drive down to Bikesport and want all their money back.
I wouldn’t be happy if I paid for a bike that wouldn’t shift.
“the minimum size tooth count for a Shimano Dura-Ace front derailleur is 39 teeth”
i have two tri bikes in my garage. one is entirely shimano ultegra, 53x39. the other is entirely shimano save a wippermann chain and a 34/50 compact drive crank. in my wildest dreams could i wish the front derailleur performance of the ultegra came close to matching what i get out of the compact drive crank which, in the thousands of miles i’ve placed on it, has yet to innapropriately derail once.
shimano has two things going for it. first, that either way you’re still using its shifting system. second, FSA can’t make its cranks fast enough to meet the demand.
Tom,if shimano thought there was any “safety” issue,why would they let FSA make there cranks with octolink. My FSA alum is octo. I imagine FSA had to pay propritary(sp?) for that.
On our last Tuesday evening ride a rider dropped a chain on an uphill sprint, went over the bars, destroyed a new Giro Atmos helmet and sustained minor injuries.
Also can not one drop a chain in any set-up. Though I agree it is more likly on the compacts. I found I need to shift my cassette first on my compacts to avoid this. Is not this a buyer beware? Or once again has our society become so litigous(sp?) that everything is someone elses fault.
