chain jumps in certain gears...

[gmcn1965]

hey people,
i have had the bike for 3 months, the gears are beginning to show some wear and tear.
i presume a tweak here or there will sort the bike out - good machine, does the bizz for £100!
the thing is i haven't had a bike for long years (shame!) so i forget the diagnosing and the fixing,,,,,!!
i am guessing the back wheel could be moved further from the big sprocket thing....oh crumbs will forget my name soon!
the chain jumping happens mostly when i am putting pressure on the bike , going uphill.
not a good time for the chain to jump ....
perhaps new chain needed?
anyways what thinkest thou?
george

 

[4F]

Is this a new bike ? How many miles have you ridden on it ?

 

[guitarpete247]

If new bike it wants to go back for service. If it's an old bike it could be that the chain has stretched. Have a look here. Unfortunately if it has gone on for too long you will probably need to replace the freewheel block/cassette as well. A chain wear indicator like this could be a useful tool for the future. If the bike has an old 5 or 6 speed block/cassette are not too expensive. Have a look on ebay for bits like this (5 Speed) or this (6 Speed).

 

[gmcn1965]

If new bike it wants to go back for service. If it's an old bike it could be that the chain has stretched. Have a look here. Unfortunately if it has gone on for too long you will probably need to replace the freewheel block/cassette as well. A chain wear indicator like this could be a useful tool for the future. If the bike has an old 5 or 6 speed block/cassette are not too expensive. Have a look on ebay for bits like this (5 Speed) or this (6 Speed).

it's an old bike - perhaps stretch , meaning new chain and block/cassette?
incidentally what is the block/cassette?

 

[4F]

incidentally what is the block/cassette?

The bit on the back wheel

 

[guitarpete247]

it's an old bike - perhaps stretch , meaning new chain and block/cassette?
incidentally what is the block/cassette?

If you look at the links I have put in this (5 Speed) or this (6 Speed) they link to ebay and examples of freewheel blocks and chains. This is a freewheel cassette. The advert says "Old and well used ,but would do for winter bike or mucking around". Personally I would avoid this and go for new if you're going to change it. If it's old and well used it will cause you the same problem of slipping gears if you fit a new chain. Here is a much better buy. As you can see they are not too expensive unless you are going for 10 or 11 speed. Your local bike shop would fit it for a reasonable amount.

 

[gmcn1965]

If you look at the links I have put in this (5 Speed) or this (6 Speed) they link to ebay and examples of freewheel blocks and chains. This is a freewheel cassette. The advert says "Old and well used ,but would do for winter bike or mucking around". Personally I would avoid this and go for new if you're going to change it. If it's old and well used it will cause you the same problem of slipping gears if you fit a new chain. Here is a much better buy. As you can see they are not too expensive unless you are going for 10 or 11 speed. Your local bike shop would fit it for a reasonable amount.

fangs a lot everybody,
especially mista guitar........i will find a cassette thingy and also investigate 7 speed chain - presuming it's a wee bit longer than a 6speed ??
chain has grown by 0.5 inch over 12 links, time to change...
ebay looks good - the shops in crawley are monopolistic and have crazy prices......the simplest widget costs a wad!!

cheers muckers,
george

 

[Davidc]

If you go to a web site called bicycle tutor and look through their videos (you can download the lot for a small fee) they'll give you all of the terminology and show you the basics of fixing most things.

 

[battered]

Jesus, are you serious that 12 links measure 12.5"? If so then the cassette (cluster of gears at the back) will be well worn. You night get away with the chainwheel (the gears attached to the pedals).

 

[PpPete]

Have a look at Sheldon Brown's site to determine whether you have cassette or freewheel. Old steel freewhel may not suffer even with that amount of chain stretch. Are the teeth shaped like "shark's fins" if so it needs changing. If cassette, with that much chain stretch then deffo need new cassette.

6-7-8 speed chain is all the same thing. Will work on 5 speed too. No difference in length.

 

[fossyant]

New chain / new freewheel sorted..............

If you know bugger all about bikes, then it's a shop job...............

 

[guitarpete247]

As davidc said Bicycle Tutor is a good place to start. It will also give you an idea what tools you might need for each job. Sheldon Brown is also a good site for searching for hard to find info. You'll probably find that a lot of other sites direct to the late great Sheldon. Once you find whether you've got a freewheel block or a cassette you can determine what tol you need to remove it. You might need a sturdy vice to hold things as over the many years it has been on it will have just got tighter and tighter. Here's where your LBS might be neccessary. A chain tool is always a good tool to have and you will need one to get your chain to the correct length. Sheldon here has a page on chain maintainance interesting reading if only to make you check it regularly .