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Wrenches: any idea on this front derailler?(7 posts)

Wrenches: any idea on this front derailler?Applejuice
Apr 4, 2002 8:07 PM
I'm not a mechancial genius, but I know my way around a bike. That said, my experience with road bikes is limited. My friend brought over his R600. He asked me to look at the fr dr. So I did.

First, he has 105 shifters, Tiagra fr dr and 105 r dr. Cranks are Cannondale EX. Dual rings: 39-53.
PC59 chain.

I started running through the gears when I noticed the front shifter pod goes up from the 39 to 53 fine. But it comes down in two steps. There's an intermediate in which the chain stays on the big ring but drags. Then, if I click it again, it comes all the way down.

Could this be a triple shifter with a double crankset? Why are there TWO steps down? It's as if it were for a triple fr dr.

Please let me know.

Thanks, Aaron
ahh...jawa
Apr 4, 2002 8:19 PM
depending on the year of the shifter it most likely is a triple shifter. What you need to do is set up the deraileur with the shifter with all clicks clicked(or in the lowest gear). Then you need to set the f.der lockout so the final click is not used. Also there are some intermediate clicks for chain line trimming.
One moreApplejuice
Apr 4, 2002 8:48 PM
The barrel adjuster near the shifter - how does it work? Is it the same as a mtb? It seems that I spin it in either direction and nothing happens. I know how barrel adjuster work, but is it different on a road bike?

Thanks again.
One morefuzzybunnies
Apr 4, 2002 9:22 PM
what do you mean near the shifter? sometimes there's one installed in the housing and works by twisting counterclockwise to create tension but never seems to work very well. The other is on the frame and again works by twisting counter clockwise, if you're not getting tension from twisting this one than it's already all the way out and you need to screw it back in and take up the slack at the derailleur.
I believe the technical term is "trim."KLM
Apr 4, 2002 11:33 PM
Depending on what rear cog you are in, the chainline will require a slight movement of the front derailer to keep it from rubbing the chain. The extra "click" you are getting could be an adjustment for derailer trim. Or, it could actually be that the shifter is designed for a triple crank. See if you can find the model number of the shifter and go to Shimano's website to find out for sure. My bet is that it's just a trim adjustment.

Best of luck,
Ken
I believe the technical term is "trim."Chen2
Apr 5, 2002 6:32 AM
I believe all of the Shimano STI shifters except Dura-Ace are double duty, meaning they use the same shifters for double and triple crank-sets. The trim stops are really more for use with the triple. A properly adjusted double should not need trim stops.
~Al
Not true...KEN2
Apr 5, 2002 8:25 AM
"A properly adjusted double should not need trim stops."

Not true--whether you get cage rub on the front derailleur on a double depends on several factors, but the shorter length chainstays on many road bikes means that there is a greater chain angle from front to rear and thus chain rub on many bikes even in the second and third cogs from the inside or outside, when combined with the opposite chainring.