Author Topic: need front derailer  (Read 3668 times)

jags

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need front derailer
« on: August 13, 2009, 07:28:43 PM »
 can somebody please reccommend for me a really good front derailer for my thorn sherpa.im running at the moment shimano xt m770 front and back.the problem with the front derailer i can't get into the big ring ,no matter how much i try to adjust it.i have those on line adjusters fitted but there useless so to save my head from been wrecked trying to fix it i'll buy a new one, so what works best troble free.
thanks
jags

blair

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Re: need front derailer
« Reply #1 on: August 14, 2009, 01:21:50 AM »
What crankset do you have on the bike?
If it's a Shimano with external bearings, there are spacers that set the chainline. Make sure these are correct, and that the RH crank is not too far out.

I assume you have wound the limit screw out far enough to allow the cage to move over.

I've been running Shimano 48-36-26 cranks with Tiagra front derailleurs on 2 different bikes for a while.

I did find that I needed to rotate the front derailleur mount at one stage to get good gear shifts. I suspect it was bumped out of alignment at some stage.
On my wife's bike, I had to adjust the positioning vertically after I changed the crank size.

As usual, Sheldon Brown (RIP) has some words of wisdom here http://sheldonbrown.com/derailer-adjustment.html
He includes the warning:
"Front derailer adjustment is not an exact science. It requires a good eye and a bit of patience to get it right."
I couldn't agree more!

If you have a good bike shop near you, it would be worth asking for help.
Trying to get the front derailleur working right can be a very frustrating experience, particularly with a triple crankset, but changing to a different device will not necessarily help. For what it's worth, I've had bikes with a range of different Shimano front derailleurs, (Alivio, Deore, Tiagra, 105 double) and have always managed to get them working eventually.

Good luck!



blair

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Re: need front derailer
« Reply #2 on: August 14, 2009, 05:13:32 AM »
More from Sheldon Brown: http://www.sheldonbrown.com/front-derailers.html
"Indexing  Road/MTB

    The ratio of cable movement to derailer movement differs with Shimano's "road " vs. "MTB " front derailers. This can cause indexing problems if you use a "road" front derailer with upright handlebars or a "MTB" front derailer with drop handlebars. This is a concern if you are running an indexed front shifter, such as Shimano STI or RapidFire shifters.

    It is not a problem if you are using a friction system, such as bar-end shifters or downtube shifters. It is also not a problem with ratcheting systems such as Campagnolo Ergo.

    Shimano does make one model of triple front derailer designed to work with "road" (52-42-*) chainrings and RapidFire upright-handlebar shifters, the R440 model. "

If you have STI shifters, looks like you need a road derailleur.
The Tiagra would probably be the best match, as it's designed for a 9-speed setup & a 50-tooth chain wheel.
It should still work with a 44-tooth chainwheel, but you might get some trimming problems if you are cross chaining.


jags

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Re: need front derailer
« Reply #3 on: August 14, 2009, 01:43:22 PM »
blair thanks for that. i eventually got it working with the help of my son (can't take all the credit).
all the gear drive train  is shimano xt m770 and tiagra 9 speed sti shifters.have to say when it's working it's perfect, but every now and then this front derailer need's adjusting.
have it working properly now so i'll leave well enough alone.
thanks again

jawj

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Re: need front derailer
« Reply #4 on: August 15, 2009, 05:26:36 PM »
Front derailer fettling is one of the biggest headaches going... unless you are brave!

Several years ago, and inspired by Cap'n Sheldon, I figured a little 'tweak' wouldn't hurt as stoopid front mechs are basically just two plates of metal that bash the chain from side to side (and we're still using this technology in twenty-oh-nine...?)

And voila! Ever since then reticent front mechs have had these tools applied, to great success:

1) The sadly missed brake-bending tool: http://store.shopping.yahoo.co.jp/atomic-cycle/4-pa-bt-3.html

2) The quite exciting, well-thoughtout and generally rather good: http://www.parktool.com/products/detail.asp?cat=14&item=DT-2

3) And if they aren't to hand there's always ol' faithful: http://en.fotolia.com/id/11004046

So be brave, and tweak your FD!