Chain keeps coming off front cog?

[karl101]

Hello,
On my Wisper 905SEL the chain keeps on slipping off the front cog and going in the space between the chain guard and the cog, this morning on the way into work it was particularly bad.

Any ideas what could be causing this? I can't see any broken teeth on the cog.

Thanks
Karl.

 

[Deleted member 4366]

Hello,
On my Wisper 905SEL the chain keeps on slipping off the front cog and going in the space between the chain guard and the cog, this morning on the way into work it was particularly bad.

Any ideas what could be causing this? I can't see any broken teeth on the cog.

Thanks
Karl.

Check in this sequence:
Have a look at the bottom bracket bearings. Grab one of the crank arms and push and pull it to see if there's any play.
Next. look from the top and rotate the crank. Does the chain-wheel run true? If it doesn't, it cab be because of damage (crash) or broken BB bearings.
Moving backwards, the next possibility is the chain. Has it got any seized links - normally due to rust?
Finally, on the back of the rear derailleur is a tension adjusting screw. Is there enough tension on the derailleur and does it move fore and aft smoothly against its spring?

 

[Cakey]

How many miles on the bike ?
All of the above comments are places to look . Chainrings , cassettes , chains wear out . Check the length of the chain , should be 12 inch exact between , pin to pin link . Also the chain ring teeth tend to sharpen when worn and make the chain slip off . If the chain has worn the teeth do not mesh in the gap and ride on the chainring points till it slips off .
If you swap the chain, usually cassette has to be done with front chain ring . Otherwise it jumps / skips

 

[eddieo]

the SEL's only came out last year...

 

[yselmike]

It happened to me, the problem is the chain just got filthy so I have to clean it at least once a week during wet/winter
weather,I have a Panasonic with dual drive.... its a pain my bike just gets filthy luckily I can wheel it into my shower
and clean it with dirt juice and fork cleaner and de-greaser and wd40 and then dry it and the lube it and spray the forks
and polish my bike gleams but my bathroom looks like a garage.

 

[yselmike]

Oh and to get to the chain and all the gogs to do a proper clean I have to remove the pedal otherwise I can not
totally remove the chainguard.

 

[karl101]

Thanks for the replies, I've checked the bracket and chain-wheel as d8veh mentioned and both are OK. I've cleaned and re-oiled the chain as much as I can, and cleaned the derailleur both were rather dirty. I'll find out in the morning if its improved.

I was going to take a link out of the chain as it seems to sag a little but I couldn't find the tool for doing the chain links (can't remember if it has a proper name), If its still causing trouble I'll have a proper look this weekend.

Karl.

 

[Jimod]

This has happened to me 3 times lately. It turns out it's my foot catching the chain as I pedal. I must be sitting differently these days. I had the seat tube out so maybe I've not got the seat straight.

 

[Deleted member 4366]

Did you tighten the derailleur tension with the little screw at the back. It will add tension to the chain if it's stretched a bit and sagging.

 

[karl101]

Did you tighten the derailleur tension with the little screw at the back. It will add tension to the chain if it's stretched a bit and sagging.

I turned it clockwise a few times, but didn't see much difference.

 

[Deleted member 4366]

I turned it clockwise a few times, but didn't see much difference.

You won't see much, but that screw winds up thr spring that makes the derailleur pull back on the chain, which increases the tension. If your chain was bouncing off because of not enough tension, then increasing the tension by this method will solve it. It has the same effect as removing link from the chain, but it's a lot easier.

 

[karl101]

You won't see much, but that screw winds up thr spring that makes the derailleur pull back on the chain, which increases the tension. If your chain was bouncing off because of not enough tension, then increasing the tension by this method will solve it. It has the same effect as removing link from the chain, but it's a lot easier.

Thanks, I tightened it a little more before setting off to work this morning. The chain behaved and the derailleur changed the gears much easier than yesterday.

 

[paulhipwood]

I have three or for chains for each bike.
I rotate them every few hundred miles.
The idea is to make sure that the chainwheels (they wear due to chain wear)

Look at this link Chain Maintenance Sheldon's passed away a couple of years ago but he was bike mad.

 

[Wisper Bikes]

Thanks, I tightened it a little more before setting off to work this morning. The chain behaved and the derailleur changed the gears much easier than yesterday.

Great news Karl, if you experience any more problems please drop me a line or take the bike in for a once over by our local service centre.

All the best

David