Chain keeps falling off

whitestar1

Hi All
My son's Trax TFS.2D full suss chain keeps falling off. I cant say if he is using the gears right. He's very upset about this. I been a full noob in this bike business dont know what to do. Any help please?

Frodo1095

Whereabouts is it falling off, at the front or back, when he is riding on the flat, going uphills, doing jumps etc ?

cooldad

Mech limit screws need adjusting?
Chain too long?
Mech lost tension?
Shifting into granny under tension?
Just happens sometimes?

Front or back.?
Which side of cassette/chainring?

robertpb

Adjust the limit adjusters

whitestar1

Not sure where, when or how. He's pretty upset and I can't get a straight story out of him. Some mate of his already tried removing links (of which I am now upset about!). From what I can see from comments here, I will have to look at the rear derailleur limiting adjusters. Thanks all for your input. This will be the first thing on my agenda when I get home today.

nicklouse

you really need to fing out where the chain is coming off.

I will be most likely the crankset end.

I would also check the Big Big gear combo as it may now be a NO NO due to the shortening. If so look at a new chain.

cooldad

Ride with him and see.

whitestar1

I have had a look at it with my son holding the bike. The chain gets off at the rear on the big cog (1). I place the chain on the tiny cog (6) then release the cable to the gear, then messed around with the H and L screws. Now it wont go to 1 on the right handle but the chain goes to the big cog (1) in the rear. Think it skipped a middle cog. Anyhow my son rode the hell out of it around the estate and thinks it fine. Yep he is on my case that I sorted one problem and created another Well what did he expect from a noob Didnt play with that fine turning numb or that screw on the inside of the mech.

cooldad

You need to adjust and index the mech properly.
Check Parktools link in Nicklouse's sig

nicklouse

but first check that the hanger has not been bent.

diy

Also if idiots have faffed about with it, they might have bent or made stiff some of the links which will cause it to jump more easily, so if its prone to coming off it will more.

Check the chain is sized correctly too (see workshop guides for that).

hang it from the garage ceiling and go through the gears and follow the park tool guide or Sheldon brown guide for gear indexing.

whitestar1

Hi All
Still having problems with the rear mech. The chain nolonger falls off. I have played with the H/L screws and fiddle with the other screw that causes the derailure to move in/out. The problem is that it jumps a cog. Its the 4th one.

nicklouse

does everything match?
bent mech hanger?

whitestar1

nicklouse wrote:

does everything match?
bent mech hanger?

Yep bent mech - actally worse. Gave up with it and took it to Decathlon. That in itself says a lot - I did buy it from Halfords! Anyhow the replaced the the entire rear mech so its alright now. Thanks to you all for the help. It taught me a thing and two.