Front derailleur question

[junkie_ball]

Hi all,

I have a specialized tricross and have basic knowledge of bike repair so please bear with me. I had an issue whilst out on a ride today 12 miles in when i changed the gear on the front chain set the chain started jumping off when changing gears in both directions. The chain is jumping off as if the the derailleur stops have been set too far in both directions sending the chain past the gear.

I have never messed with gear indexing i usually leave this for my local service shop. The thing is the bike was only serviced 100 miles ago and until this morning the gears had been functioning smoothly. I'd like to avoid avoid taking it back to the service shop for them to sort if poss. Does anyone have any idea of what could have moved / stretched / come lose to cause this?

This is the spec bike i have albeit i have the 2013 model not 2014.

 

[Cycleops]

Sounds like the adjustment stops are indeed set wrongly. Rather than try to explain here have a look on YouTube for videos.

 

[junkie_ball]

Thanks for the reply can the stops move that quickly though? As i said i have not had any issues previously and all of a sudden it started happening on every gear change? I haven't had any warning such as gear changes being slow ?

 

[Kbrook]

Is it jumping off both big ring towards the pedal and little ring towards the frame? Assuming it was set correctly before the only thing I can think is that someone has been messing with the stop screws, can't think of another reason this would happen, particularly off both chainrings. Will be interested what others say.

 

[Cycleops]

If the bike is quite new the cable may have stretched. The stop screws will limit travel at both extremities.

 

[junkie_ball]

Is it jumping off both big ring towards the pedal and little ring towards the frame? Assuming it was set correctly before the only thing I can think is that someone has been messing with the stop screws, can't think of another reason this would happen, particularly off both chainrings. Will be interested what others say.

That is exactly what has started happening. But can say 100% no one has touched the stop screws as I've been the only one to ride, clean or general touch the bike.

If the bike is quite new the cable may have stretched. The stop screws will limit travel at both extremities.

The bike is fairly new i did take the bike in to have the gears reset after approx 60 miles, I guess it may have been the case cable may not have really stretched when they checked it over. May attempt to tighten the cable although never done it before if i mess it up will have to take it into the shop to get them to adjust correctly.

 

[mrandmrspoves]

Cable stretch could explain why the chain comes off when you change to low gear - but wouldn't explain why it does in high gear. I would give both High and Low stop screws a tweak. Start off with one full turn in a clockwise direction and if the chain still comes off continue in half turn increments. Once you have that sorted put your front derailleur into low gearand with the chain on the smallest chainring feel for any slack in the front gear cable. It should be adjusted so that it is just taut but not pulling the derailleur. NOTE when you are adjusting the gear cables remember that there may be another tensioner on the cable - if so screw this in clockwise until it won't go any further and then back it off quarter of a turn so that it is less likely to seize. This adjuster is then ready to take out small amounts of slack in future.

 

[Cubist]

Adjust limit screws by eye rather than trial and error. Get the bike in enough light to see small gaps etc then put the chain on big ring smallest sprocket. Wind the limit screw on the front mech so that there is a mm or so of clearance between the inside surface of the outside of the mech cage, no more. While you're at it, check that the cage is no more than 3 or 4 mm above the teeth of the chainring, and all lined up fore and aft. Could be that your clamp has slipped.

Now, shift to small chainring and undo the clamp bolt holding the cable to the mech. Put the chain on largest cog and again, adjust the limit screw so that there is no more than a mm clearance between the inside edge of the inside cage plate.

Now, wind the barrel adjuster on the cable all the way in, ie a slack as it will go, then back it out by two full turns. Pull the cable through the mech clamp by hand, and clamp so that the cable is taut, but not under any tension. Put the chain on the middle of the cassette and try to shift up to the big ring. You may need to add or release cable tension via the barrel adjuster to get a smooth shift, and this take s a bit of trial and error, but at least now you know it isn't the limit screws causing the problems.

 

[junkie_ball]

Ok sorry for the delay in giving an updated. First chance i had to look at it this morning. Cable did indeed need tightening seems to change fine whilst in the comfort of my dry garage will find out how the adjustments went when these gales subside.