Big Cog Clag Blog

[ChrisPAmbulance]

Hi all,

This is my first question here, but it's been bugging me for a while.

I have a very old Raleigh Raven (27 yrs to be exact), from back in the days when they were called ATBs rather than Hybrids. I have a problem where the chain slips off the front deraileur when changing onto the innermost (ie. biggest) cog. It slips inward onto the bottom bracket leaving my legs going a million rpm and the bike going slowly backwards !!

A big however is that it only does this when I'm on the bike, when on the maintenance stand the whole mech works perfectly.

Here are a few clues.
1. I weigh 18 stone, so there is a lot of stress on the frame and everything attached to it.
2. I only use the big cog when climbing hills, so this also addes to the strain that the chain et al is under when the slip occurs.
3. Even when it works, getting onto the big cog is always an effort, often requiring severl attempts at a gear shift.
4. I have to plead guilty to this bike having had minimum/mal maintenance over the years as I am of the opinion that if it ain't broke, don't meddle with it or it will be. So it's still the same chain as I bought back in the 1980s.

Any ideas. It's starting to get embarrassing, especially when being passed on a hill by a mob of hungry canondales like the last time I came back from Newport . And I have suffered a few bouts of chin music when this happens.

 

[ChrisPAmbulance]

PS. The chin music is from my chin gently making contact with the handlebars as I lose the chain, in case you were wondering.

 

[PpPete]

Why is the big cog at the front in the innermost position?
Why are you using the big cog at the front for going up hills?

Normal practice is to have the smaller cog at the front on the innermost position and to use that one for climbing.

27 years out of the one chain! Chances are the whole drive train is now shot - and frankly the replacement cost is likely to be greater than the value of the bike.

Learn about derailleur limit screws to stop the chain falling off ... and by the time you are up to speed on basic maintenance skills it will be time to buy a new bike.

 

[ChrisPAmbulance]

Oh Dear - cheers PpP,

You don't know how embarrassed I felt at having realised what I put when I looked at the bike this morning and thiought - here, hang on. Of course the big cog is on the outside and the chain falls of the smaller innermost one - FOOL !!

Actually, I have adjusted the limiter screws on several occasions and like I said it works perfectly well on the stand which is what confuses me. But you are talking to someone who's better half hides the tools because of what his DIY has done to the house over the years !!

I have been experimenting today with changing very gently and I have had "some" sucess, but all that came to nothing when we took a dive into the River Sow at Seighford this morning when the surface water proved much deeper than I expected and the back-resistance beat me when the water got above the pedal level.

As for that age of the bike - too old, too creaky and should have been sold for scrap years ago - I kind of like a bike that reflects my personality. Luckily we have a local charity here called Back2Bikes which does maintenance jobs relatively cheaply, so It is time for another donation.

Thanks for the advice, I'll attack the limiter screws - again.