Gears / Chain help

[Branwen]

Since getting my bike serviced a couple of weeks ago I'm having nightmares with the chain or the gears, I'm not sure which the problem is. Twice the chain had got all knotted and doubled back on itself at the front, and regularly the chain is slipping & jumping at the back, especially when it's on the smaller cogs. Aaaarrrggghhhh any ideas? Thanks

[Oggy]

Where did you get it serviced? hard to say without seeing it but probable causes could be one of the following

stiff link in chain
gears not set up properly
worn drivtrain

did they replace the chain when they serviced it?

[thistle]

Did they replace anything (gear cables, chain, chainrings, cassette) when they did the service?

A slipping chain on the rear, especially on the small ones is often because the chain has stretched. When the chain stretches it wears down the cogs to fit the slightly longer chain, and if you just put a new chain on it doesn't mesh properly.
If you measure 12 pairs of links on the chain it should be exactly 12 inches long. There is more info here sheldonbrown.com/chains.html#wear

The chain knotting itself up on the front sounds like 'chain suck' and happens if the front cogs are worn. There's some detailed information here fagan.co.za/Bikes/Csuck/.

You might need a new cassette, new chain or new chainrings. Often the middle chainring wears faster than the others because you use it more often. If it's just that one that's worn you might be able to just replace the ring £10-£15) rather than getting a whole set of chainrings (£50+)

If you can make it to a forum ride soon someone might be able to have a closer look and work out exactly what the problem it.

[Deleted]

Reasons as said above so I will not repeat them.

Surely if this has only happened since having it serviced then your best action is to return the bike asap and get them to put right what is wrong, if they serviced the bike for you then it should be done correctly, if not then they must put it right. Being a few weeks later tell them it's the first chance you've had to ride the bike since it was serviced and the chain is jumping and skipping etc.

If they replaced the chain then they should have known about wear affecting the rest of the drivetrain and sorted it accordingly.

[Branwen]

Thanks for the replies guys. I took it back the day after it was serviced because of this . . .



and the guys at the shop looked at it straight away but couldn't see anything wrong.
The gear cables were changed during the service but that's all . . . I've tried to keep the chain clean and stuff
I wonder if the chain has stretched when the above happened?? I can see it 'jumping' on the small cogs under no pressure at all, when I spin the pedals with the bike upside down so you can imagine what it's like when being ridden. hmmmmmm.

I'm on a lot of courses for the next few weekends but will try and get onto the next beginner ride.

Thanks again!

[Deleted]

Sounds like cable stretch and or improper indexing, very simply to adjust, the link below may help you, if not someone on a forum ride will do it for you.

www.youtube.com/watch?v=pfLHRIdMem0 - this vid only shows the barrel adjuster on the rear mech, you will also have one on each shifter where the cable comes out for further adjustment.

There may be better videos out there.

[Branwen]

12 chain links measure 12 inches so least I know the chain hasn't stretched. Thanks for the links and ideas everyone - very helpful

[46neil]

Hi Branwen I would say it's set up of the cables as if new cables have been fitted they will stretch and will need readjustment after use, I would also make sure the gears are clean and lightly oil the chain and gears.
If all else fails take it back to the shop.
I also think it's a bit strange to change the cables on such a newish bike.
Hope this helps.