Can you lengthen the cage on a front mech?

[yello]

The chain on the bike I'm building up rubs on the bottom of the front dérailleur cage when on the granny and the smallest 4 cogs. The mech itself is as close to the big ring as I'm going to get it (height wise) so I've no further room for vertical adjustment.

One answer seems to me to be to lengthen the cage somehow... I probably only need a couple of mm. Do you reckon I can take to it with pliers and try and squeeze some extra length out of it?! Or would it bugger the mech?

 

[Landslide]

I suspect you'd bugger it. Are you running a triple chainset? Sounds to me like you'd be better off changing up a chainring earlier so you don't end up in small/small chainring/sprocket combinations - should avoid the chain rubbing on the mech and your chain will be happier running straighter.

 

[spandex]

You can by going to your LBS and giving them some Cash and say can I have a longer cage FM Please. Dont forget to say Please as they may give you the wrong thing

 

[yello]

Sounds to me like you'd be better off changing up a chainring earlier so you don't end up in small/small chainring/sprocket combinations.

That's always an option as I know you shouldn't ride 'across the block' (big to big, or small to small) anyway, but in my case we're talking small to FOUR smallest! It's a triple and I am kinding of thinking (hoping!) that if I needed the granny, it's bail out time and I'm looking for the big cogs anyway!

Spandex, twire it that simple! Getting a compatible mech is not that easy! According to the specs, the one I have should work...

 

[spandex]

Yello tell me more what are you running (size of cogs...), what mech, shifters,

 

[yello]

All deore XT 8sp of differing ages, a 24/36/48 triple but the front mech is new. I spent ages trying to find one that'd span the 24 tooth gap... but I reckon that's still my problem. I wish I had a 46 tooth ring sitting around because I'd like to see what effect that has.

 

[spandex]

Say it is the right one? see if when its sitting in top chain ring that it is 3mil from the ring and is in line with the rings. If it is all XT it will fit

 

[GilesM]

All deore XT 8sp of differing ages, a 24/36/48 triple but the front mech is new. I spent ages trying to find one that'd span the 24 tooth gap... but I reckon that's still my problem. I wish I had a 46 tooth ring sitting around because I'd like to see what effect that has.

The 24 teeth gap should be no problem, most triple MTB chainsets are now 22, 32, 46, so again you have the same spread. I wouldn't normally use the granny ring and smallest four sprockets, as already mentioned I would be back on the middle ring if I needed to change up. Is the front mech definately as low on the 46 ring as possible. As for increasing the length of the cage, it could be done, but I wouldn't try it myself, if you damage the cage then it definately won't work properly. Did you have the problems before you change the front mech, is the old and new one obviously different.

Giles

 

[yello]

I'd say I've got less than 3mm from top ring to mech! I've brought it down as low as it will go. It's old 8sp and I've been doing a bit of googling. I reckon it's an M738 mech. If that's the case then it'll only serve a 22 tooth gap, a 10 tooth mid to outer span and a max of a 44T outer....

...if that's all true, I'm not quite sure just yet of my easiest/cheapest way to resolve... reckon I've got to focus on what I want to achieve and work backwards...