Chain keeps skipping

rabjoshu

I have a bog standard 21 speed racing bike and have not learnt how to repair or fix it. Recently when I change gears the chain keeps skipping on certain gears, I presume I need to replace the chain and cassette. I want to buy these online. How do I find out what the correct size of the cassette is and the length of the chain?

petethedrummer

What type of gears have you got? I presume Shimano so...

Here's a cassette: http://www.chainreactioncycles.com/Models.aspx?ModelID=38302

Here's a chain: http://www.chainreactioncycles.com/Models.aspx?ModelID=38332

The chain will come with extra links so you just need to count the number on your existing chain and cut it to length using a chain tool.

Heres a chain tool: http://www.cyclesuperstore.ie/shop/pc/viewPrd.asp?idproduct=7440 .. I have a BBB one similar to this and its the best one of the 3 I've owned so far.

Someone else may be abe to tell you if there are compatibility issues if your bike is very old.

C3PO

My guess is that the OP won't have a chain whip or cassette removal tool either? And the problem may not even be the chain and cassette! Might be better to go to your LBS, if you have one near you, and let them sort it!

kennyb3

How long have you had it? might just need its 4/6 week tightening after buying.

Either way im with RPL1 go to you local bike shop and get it serviced before buying parts.

petethedrummer

You'll never learn if you don't make a hash of it a few times.

Keep_Her_Lit

rabjoshu wrote: »

I presume I need to replace the chain and cassette.

Maybe not. Before going to the expense of buying new components, it's worth checking that your current set up is otherwise in good working order and properly adjusted. A few things you can check:

1. Is the chain well lubricated?
2. Can you spin the pedals backwards freely?
3. Do the jockey wheels in the rear mech spin freely also?
4. Are the shifter cables and cable outers in good condition?
5. Does the shifter move easily from one gear position to the next?
6. If the gears are indexed (the shifter "clicks" into a designated position for each gear), is the indexing correctly adjusted? If it is, the chain should move freely from one sprocket to the next, for both up-shifts and down-shifts. Also, once in a given gear, everything should turn smoothly and freely, without any rubbing, clicking or rattling noises.
7. Has the bike been crashed? If so, take a look at the point where the rear mech is screwed to the frame - is anything bent or misaligned at this point?
8. Does the skipping occur only when you're pedaling hard? Or does it occur even when you're off the bike and turning the pedal by hand?
9. Is it skipping on only one sprocket at a time or is it jumping back and forth between two adjacent gears?

If the skipping is really due to chain and/or sprocket wear, then this can easily be measured (in the case of the chain) or seen (in the case of the sprockets). In any case, I think you should first establish why the chain is skipping, then decide what needs to be done to remedy it, otherwise you may end up wasting time, effort and money.

If your bike is only a few years old or less, then a 21 speed drivetrain almost certainly means that it is equipped with low-end components. In that case, it's quite possible that higher spec'd components may be incompatible (e.g. does the cassette slide onto the rear hub or screw onto it? If the latter, then most cassettes you can buy on-line will not work for you).

HTH

Icyseanfitz

petethedrummer wrote: »

You'll never learn if you don't make a hash of it a few times.

i should be running my own bike shop according to that statement

petethedrummer

Fingers Crossed MTB Tuning Ltd.

Proprietor: Icyseanfitz