Front mech issues

[Nozzer]

On my cannondale f4oo, the front mech has stopped working, when i change gear the cable just goes all floppy, has the mech seized?

 

[Zoiders]

Yes, Deore and Alivio front mechs are know to seize, often if you only use the one ring most of the time.

Take it off and leave it to soak in white spirit over night or for an afternoon, scrub the crap off, dry it, relube the pivots and adjustment screws, refit.

If this fails - buy a new one.

 

[Nozzer]

Yep it is deore and i mainly use 1 ring. Ive soaked it with wd 40 etc, not over night admitedly. Ill try that. The rear mech is sram x7, perhaps ill get a front one of those

 

[Nozzer]

Just looking at different front mech's, how will i know what size etc to get, looking on chain reaction and there are loads of different sizes. Bike is 2007 cannondale F4

 

[Zoiders]

Shimano MTB mechs tend to be one size - they supply plastic shims in the packet for different tube diameters.

 

[RecordAceFromNew]

Just looking at different front mech's, how will i know what size etc to get, looking on chain reaction and there are loads of different sizes. Bike is 2007 cannondale F4

Indeed they do sell them in different sizes. If you don't have a vernier (sold in Poundland) per picture below for measuring tube diameter, you can wind a piece of thin light coloured cotton a few times tightly around the downtube near the front mech, and use a thin marker pen or some such to draw a thin line vertically down across them. When you have unwound the cotton measure the distance between adjacent marks in mm (should all be roughly equal if done right) and divide by 3.14. That would be the diameter of your downtube (because tube circumference is 3.14 times diameter) and is the size for which front mechs are sold.

Downtubes generally come in 28.6mm, 31.8mm or 34.9mm which are approx 10% apart so the above method should be accurate enough to figure out which one you have/need.

 

[fossyant]

You should be able to salvage the mech with some TLC. Front mechs don't do much. Advice is give a squirt with WD40 after any crappy rides just on the pivots.

 

[2Loose]

Last winter my Deore front mech seized due to salt and grit.
It did take some work to properly un-seize it, but lashings of wd40 (& custard

) and manually pulling and pushing the mech back and forth, followed by more wd40 got it free and smooth again in the end.

I would probably have done just as well by taking it off and moving it around in a bath of hot soapy water tbh. But the main thing is, you have grit in the joint and it needs to be washed\worked out.

 

[Zoiders]

Indeed they do sell them in different sizes. If you don't have a vernier (sold in Poundland) per picture below for measuring tube diameter, you can wind a piece of thin light coloured cotton a few times tightly around the downtube near the front mech, and use a thin marker pen or some such to draw a thin line vertically down across them. When you have unwound the cotton measure the distance between adjacent marks in mm (should all be roughly equal if done right) and divide by 3.14. That would be the diameter of your downtube (because tube circumference is 3.14 times diameter) and is the size for which front mechs are sold.

Downtubes generally come in 28.6mm, 31.8mm or 34.9mm which are approx 10% apart so the above method should be accurate enough to figure out which one you have/need.

As I said it's a MTB mech.

http://www.chainreac...x?ModelID=12580

One size, spacers provided.

No maths or extra tools involved at all.