Front Mech Madness....Help!

[Stevewheel]

Dear all knowing crowd......please help.

I'm having trouble with a front mech and the "bloke down the pub" can't help and I've watched all the "Expert Village Dart Carm" videos presented by young men with Armish beards, rearward facing baseball caps and trousers that need pulling up, "adjusting" the "front dur rayleigh err" on mountain bikes and it's not helping. Quite frankly i'm all at sea. Someone told me to adjust the upper screw, someone else the lower, someone said don't touch any screws and someone else said take it to your LBS. On this last point I would prefer not to do that. Partly because I think I ought to know how to do this myself and partly because visits to my LBS are reminiscent of the HiFi sketch from "Not The Nine O Clock News". I don't know the difference between woofers and tweeters!

So here's the problem...

Campag Veloce 9 speed.....rear mech silky smooth and silent...front mech silent also. If I change from the small chainring to the big chainring it requires two sweeps of the lever, the second of which needs to be held in the "change" position for the first pedal rev. Once in the big ring it runs perfectly. However, ride over a bump (not that our lanes aren't billiard table smooth you understand) or allow a grain of pollen to alight upon the thumb change lever (not to mention touching it by mistake) and the the chain quickly drops down onto the small ring. This, as you can imagine is both annoying and potentially very painful as it has caused my crutch to meet the top tube rather abruptly on several occasions. Since I don't have the testicular control or resilience of a Shaolin Monk I really would like to solve this problem.

Can anyone give me a sort of "now then Steve, turn screw A (picture attached) half a turn, turn screw B (picture attached) a quarter turn, now move away from the bike...problem solved".......it's not asking much is it? I really don't want to go back to the "Expuurt Village" or even the " LB & HiFI Shop" if I can help it.

Thanks again in anticipation of your always amazing knowledge.

[mattsccm]

This is my version. Sadly there will be others.
Just check that the mech isn't damaged and that the centre line of it, fore and aft is parallel with the chain rings. Happy?
Now identify which of those fiddly little screws control how far the mech can move inwards.(a) Also find which stops it going to far out.(b) As its raining, I have just come in and the fire and beer are warm so I am not going out to check mine. Sorry.
Have any cable adjusters about 1/3 out or maybe less.(c)
Put the chain on the biggest rear sprocket and the smallest front. Wind in or out screw (a) until the mech just clears the chain and all is quiet. Try and keep the chain tight using the brake a bit or something. that 1/3 out (c) will allow just a tad of movement if you find that its a gnat's to close later.
Now install front mech cable ensuring that the shifter is shifted to the smallest chainring first. Pull it tight and tighten. (c) allows a touch of slack if needed.
Drop the chain down the cassette to 9th. shift the chain properly to the big ring. Wind in screw (b) until the mech just misses the chain by the same gnat's.
For me that's done
(c) allows a touch of cable adjusting either way.
I would assume that someone else will be along to make another suggestion.

[CREPELLO]

Could be that the 'g' spring in the shifter is worn. It does the indexing and when worn the shifter can slip or loss the indexing. Campag dealers or service centre can supply (and fit) thes springs.

[tatanab]

You have managed to set the cable tension and the limit screw so that the teeth in the lever ratchet are only just engaging at the outer limit of throw of the front mech i.e when you change to the big ring. So any little jolt or brush with your thumb will cause the lever to release back a notch on the ratchet.

Either undo the cable tension adjuster (on downtube or head tube) half a turn, or release the outer limit screw on your front mech by half a turn.

I've had this myself when I've been setting up a front mech.

However --- having said that this cause the ratchet to release by a notch, a single click on the ratchet should not be enough to cause the chain to drop onto the little ring, so perhaps the G spring is on its way out as suggested by others.

Also - you say it takes two sweeps of the lever to change from little to large. On a triple this is what you would expect, but not on a double. Perhaps you have connected the cable to the mech when the lever is not in its fully relaxed position. i.e you need to press the little lever until there are no more clicks available before connecting the cable.

[MGate]

The little screws set the range of movement for the front mech. Prevents the mech from changing too far either way.

Explore a little bit so you understand - first use the thumb lever to change onto the small ring and press repeatedly so you know that the cable is slack. Undo the gear cable from the mech - the mech will then travel to the inside position. Try both of the little screws - one will do nothing (because it does the outside 'upper' setting and the other will alter the inside position of the mech.

Follow the cable up to the 'cable stop' there's a screw in and out adjuster - screw out tightens cable (will pull mech further out) so set that about half way so you can go up or down - tighter or slacker.

With the cable undone explore the position of the front mech - it wants to run parallel to the rings and be high enough off the outer ring to give the chain space to get up there. The other posts cover this . Pull the chain off the rings and push the mech in and out with your hand and you'll get the idea. You can explore what the other adjust screw does now - setting the out limit of movement - push the mech as far out as it will go and then adjust the screw - see it change the position?

Refix the cable by pulling through as much slack gear cable as you can then clamping.

Give that a go.

I run Veloce 10 double on one bike, Campag levers and shimano 'dee raliegh eers' triple on another and centaur 9 triple on another - once you figure out what's going on they are easy enough to set up - esp the front mech.

[gaz]

.

[Mick F]

Could be that the 'g' spring in the shifter is worn.

That was my instant thought.

No matter how badly the front mech is set up, it shouldn't move from where you've put it when you go over a bump!

First thing to check is to take your chain off and play with the mech up and down. Set it to the big ring position and push it back to small ring with your fingers. If it moves easily, your LH Ergo need some TLC.

It should take a good push with two hands to move against the G spring tension, but if it's easy, the Ergo is shot.

[Stevewheel]

Many, many thanks folks, lots of stuff to try here so I'm off to the bike shed.

Thanks again for all your assistance.