derailier chain slips off: What could be wrong?

fairweatherbiker

Hi new
I'm new to biking, and I think I've adjusted my derailier correctly, I can get all the gears with little or no noise, however - the slightest backpedal - or even wheeling the bike backwards when the gear lever position doesn't match the rear cog causes the chain to slip out of the lower jocky wheel. The only way I can ever get the chain back is to remove the lower jocky wheel and thread the chain back in, while fighting the spring mechanism. Its a messy 10-minute job I've done by the roadside too many times to be fun. I can't work out how the chain can slip out in the first place as its impossible to get back in with the jocky wheel in place. Does anyone have any suggestions as to what might be wrong?

Big Red S

When you're pedalling forwards, does the drivetrain make any noise? Halfway down the cage there's a bar across the gap, which keeps the chain in place. Are you running the chain on the correct side of it?

Does the chain skip at all under normal pedalling?

Can you get a photo of the mech set up (and, ideally, after the chain's come off)?

fairweatherbiker

Hardly any noise pedalling forwards, tyre noise on the road is more noticable. Chaing occasionally slips to a higher gear - but thats ususally after I've changed and not quite got the lever in position.

I'm a bit lost with the terminology - what is a cage - do you mean the spring-loaded derailier hanger that holds the 2 jocky wheels? - there is a small bar which stops the chain coming out - and its impossible to put the chain back in because of that bar (without removing the jocky wheel)

I'll look when I leave work and see if there is anything between the 2 wheels - and get a photo.

biondino

Do you have old school friction shifters (often on the down tube or, if I remember rightly, at the top of the headset) or the more modern indexed shifters (on the handlebar hoods on a drop bar bike)? While the problems you're having with chain slippage sounds like par for the course with friction shifters you certainly shouldn't be having so much problem with modern shifters.

fairweatherbiker

Hi biondino

I looked at your pictures on Flickr - my bike is similar to the white one - with 531 tubing. Mine actually has the same Reynolds 531 tubing - and yes the shifter is one of those levers mounted on the centre post. If I'm to assume this chain slip problem is a design problem of that old style of bike, then I should really get a new bike. I've been reluctant to get a new one as my bike only wieghs 23lbs - and anything I've looked at in bike shops is much heavier - around 32lbs+ unless I look at really expensive models.

salsarider79

32lbs????????? :shock: What are you riding???????

biondino

32lbs is beyond heavy for a road bike - would you want a mountain bike if you did buy a new one? My Trek 1200, which is a 2005 alloy model, is 24lb with lock, pedals, pump, lights etc. attached and it's by no means at the light end (my Focus is under 18lbs, naked).

Your problem sounds like an issue with the rear derailleur itself, or - possibly - a sticky chain? If the machinery is several years old, as seems likely on that kind of bike, you may need to replace parts, though a good thorough clean - ideally off the bike - might help.

Just to be the devil on your shoulder for a second, if you have the funds for a new bike I'm sure we can help you find something suitable, lightweight, with simple index shifting. Tempted?

fairweatherbiker

Absolutely tempted for a better bike.

Removing the rear gear assembly is not something I'd have the confidence to attempt, as I may mean I'm without the bike if I couldn't get it back together easily.

I could raise £200-300 for a new bike - and there ia a bewildering array of bicyle types these days - so I'll start with what I like and what I do.

I started biking in March this year, with a fairly old mountain bike, but it was really heavy, and soon after when I tried out my current bike, it was so much lighter and had so little rolling resistance in comparison, I was hooked. It was given to me free, and the owner assured me it had virtually no use, and has sat in her shed for 20 years. I had the local bike shop give it a service, new tyres and inners and it has been great - apart from the chain slip problem.

I ride to work most days: half the journey on fairly busy roads and half on the towpath, which can get pretty rough and muddy, but access is via some fairly steep steps where I have to carry the bike, so thats why I want a lightweight bike.

biondino

With that kind of budget you should look at 2nd hand bikes first. If you find links on ebay etc. post them here! Make sure you know what size you need as there's no point getting all excited about a nice-looking bike if it's obviously too big or small.

fairweatherbiker

Hi salsarider79

What I'm riding? Your're gonna laugh I know it.

Here goes:

http://www.flickr.com/photos/31188585@N07/2921722006/

And it weighs 23lbs.

balthazar

fairweatherbiker wrote:

What I'm riding? Your're gonna laugh I know it.

Nothing to be embarrassed about... I think you're just cresting the fashion curve here: mixte and 'ladies' frames are where it's at, again.

http://vanillabicycles.com/frames/commuter/2/
http://waterfordbikes.com/now/models.php?Model=655

Many, many thousands of pounds for those ones...

Bugly

are you sure its 531? or stickered 531. Have never seen a mixte/ladies made of 531. That used to be the mark of a good quality racing or touring frame.

laughingboy

fairweatherbiker wrote:

Hi new
I'm new to biking, and I think I've adjusted my derailier correctly, I can get all the gears with little or no noise, however - the slightest backpedal - or even wheeling the bike backwards when the gear lever position doesn't match the rear cog causes the chain to slip out of the lower jocky wheel. The only way I can ever get the chain back is to remove the lower jocky wheel and thread the chain back in, while fighting the spring mechanism. Its a messy 10-minute job I've done by the roadside too many times to be fun. I can't work out how the chain can slip out in the first place as its impossible to get back in with the jocky wheel in place. Does anyone have any suggestions as to what might be wrong?

Firstly, "wheeling the bike backwards when the gear lever position doesn't match the rear cog causes the chain to slip out of the lower jocky wheel." This is basically normal, although, it shouldn't be a ten minute job to correct. On my bike, the chain will bunch up on the jockey wheels, and stop the back pedalling.

However, 'the slightest backpedal', or any backpedal shouldn't matter when in the correct gear. It sounds like something is out of alignment (more likely in indexed gear systems) or is bent. Is the cage bent? Is the derailleur cage vertical, or is it wonky (is the attachment to the frame bent?). In other words, have a good look at the derailleur - see links below.

I don't advise buying a new bike because of one problem with your current one. Unless it can't be fixed. Your Coventry Eagle is a good bike with a good frame (definitely Reynolds 531 - the best tubing available from 1930s to 1980s, and still highly sought after/regarded).

http://www.parktool.com/repair/readhowto.asp?id=64
http://bicycletutor.com/adjust-rear-derailleur/

fairweatherbiker

Bugly wrote:

are you sure its 531? or stickered 531. Have never seen a mixte/ladies made of 531. That used to be the mark of a good quality racing or touring frame.

Its a sticker but why would they sticker it if it wasn't the real thing?