Tandem Cycling - Front Deraileur Question / Info
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I did some searching here and on the net looking for an answer, but so far it has eluded me.
Road vs Mountain front mechs...I realize the obvious difference between some cages, but this is not related to that.
If you have a Shimano Road type triple FD, is the cable pull the same as an off road FD.
If the road FD's have two different cable pull requirements, what model Road FD's can work properly with Off Road shifters. Is there one set of years that have short pull while later ones have a longer pull like the mtb.
Goal is to make a front twist shifter for off road work with the road FD triple, just doesn't require near as much twisting to make the shifts.
11-02-08, 11:49 PM
As far as I know, all the modern Shimano road deraileurs should work, however you need to use a "friction" version of "gripshift." Twist shifters come either as indexed or as something that is closer to a friction shifter. There are clicks, but they are very close together. The friction version is likely to work better for two reasons:
1. Tandems tend to be fussier on the front shifting. With double the torque and sometimes not ideal communication communication with stoker, there tends to be more torque on the drivetrain during shifts. With drop bar shifters, there isn't an option for friction, unless you want to run a bar end shifter for the front. It's not enough of an issue for most to resort to this, but with gripshift, it's an easy choice to go with friction and the shifting is still as easy to reach as indexed.
2. Front road deraileurs are designed to work with a trim point, while the mountain versions are not. With an indexed gripshift you will not be able to trim the deraileur and may be unable to use as many gears as you would with the friction gripshift, since you can achieve trim settings with it. This is also an issue on many recumbents which is why the friction version is frequently used on them as well.
11-03-08, 04:26 AM
On a hybrid single bike, I use a SRAM X-7 twist/grip shift with a Shimano 105 triple FD. It works very nicely, with solid shifting and easy trim adjustments. I think there are about 7 or 8 clicks through the useable range of motion, so a few clicks makes the shift and you have one click either way for trim.
11-03-08, 09:59 AM
I think there are about 7 or 8 clicks through the useable range of motion, so a few clicks makes the shift and you have one click either way for trim.
This is one of the shifter models that I am describing. Some models do not have the ability to trim.
Something else to watch out for is that some SRAM rear shifters were designed to work with Shimano deraileurs and some were made to work only with SRAM deraileurs. When you buy the set, make sure you get one that will work with your rear deraileur properly as well.
11-05-08, 12:25 AM
My 1999 Santana Rio was factory built with Ritchey SACHS grip twist shifters, and Shimano 105 FD. This shifting system has worked very well, with several trim positions in the shifting pattern. This shifting system has worked without any problems with the three different crank setups (MTB, Road, Hybrid Road) I have used on this tandem.
I've been doing more homework on this as time permits.
Information from here is great.
In regards to our front setup, as I mentioned, the bike has a triple chainring front, with an Ultegra front der (Part Number FD-6503) and a Grip Shift Extreme, index type front shifter designed for off road.
At the present time it works. The shifter does not have the proper cable pull for this front der. But it does work, with a heavy cable pull and fast dowshifts.
I checked and compared the actuation arm length of this FD-6503 Ultegra front to a mountain front and they definitely have a difference.The Ultegra has a 14mm long cable attatch arm while the off road type is 20mm. This accounts for the heavy pull and fast down shifts.
The odd part of all this is my Kestrel roadbike with 600 Front Der has the longer arm similar to a MTB, but it has two positions to clamp the cable. Depending upon which slot is used, inboard or outboard of the cable clamp bolt, one will make it actuate at 14mm like the Ultegra in question (which is where it's clamped now on the Kestrel) and the other cable slot will space it at 20mm like a MTB.
This why I believe some have minimal or no issues and why our tandem with Ultegra / Grip shift is the fastest actuating, front shifting bike I've ever ridden. My current Ultegra does not have the two cable clamping positions, while others posting here do have two clamp slots.
With a 54 tooth big ring it leaves a few options.
First is just ride it as is and deal with it. This includes normally over shifting to the inner on account of very little shifter movement for full travel of the front der. Plus a heavy pull to wind the front der on upshifts.
Second is to find another front der with this double cable clamp position, like my 600, and replace the front der. The big question is which model has this capability. Any ideas?
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