All,

What is the logic behind changing sprockets with a new bike chain? The only thing I can think of is something to do with "bedding in" and a new chain may somehow cause damage to the teeth of old sprockets but it sounds unlikely.

Basically is it really neccesary or another manufacturer con?

Cheers,

TBK

Know bugger all about two wheel stuff but on classic cars when fitting a new timing chain I do fit new sprockets as chain and sprockets have worn together and older blokes with beards told me to. If they are cheap why not? They are going to last ages.
P.s. on timing chains a new tensioner goes on as well for me.

That's a new one on me, back in the 70s and 80s I'd change the sprockets if the old ones were looking worn, although most chain suppliers would offer chain and sprockets as a package at a cheaper all in price.

Nowadays with modern chain tecnology I wouldn't like to say. Most of my bikes have been shaft driven. It is a source of wonder to me that bikes still use chains; imagine the scene at Ferrari or Porsche;

'Boss I've designed a new 200mph sports car!'
'Excellent Chef, show me the pans... why the fuck has it got a chain final drive? Go away and come back with a shaft driven beastie!'

Originally Posted by theblindking

All,

What is the logic behind changing sprockets with a new bike chain? The only thing I can think of is something to do with "bedding in" and a new chain may somehow cause damage to the teeth of old sprockets but it sounds unlikely.

Basically is it really neccesary or another manufacturer con?

Cheers,

TBK

Sprockets are cheap, chains are expensive.
A worn sprocket will wear a chain faster. Good sprockets will extend the chain life a bit.

You only really need to change if the new chain is skipping on the sprocket or rear cassette. The chain stretches over time. Well, actually it doesn't. The rollers in the links wear (through mud and grit) which makes the chain longer and this wears the teeth of the sprocket or cassette. A new chain might not be compatible with the worn sprocket, thus skipping.

Cheers All.

Ive arrived late to the party but:

You can get away with not doing it - for a while - say every second chain but its a false economy as a worn sprocket may reduce the life of the new chain and relatively speaking chains are the expensive part(and eventually the sprocket will wear out completely).

I have seen some horrific looking sprockets on tight-arse rat-bikers' bikes. Eventually the teeth of the sprocket wear to sharp points then start to bend over and finally the chain just doesnt catch at all. Only once have I known someone get to quite that point.

Best tip - buy a shaft or belt drive bike and leave the 19th century behind you. Even Harleys use belt drive! For some bikes you can retro-fit a belt drive. It would probably be the best move you could make.

Belts are the way forward. I've got an old Motor Cyclists book somewhere that says so. It points out that chains are metal and will wear very quickly. Somewhere I've also got a small tool for removing/ replacing leather links.
I've had a quick look, can't find it at the mo', it was printed pre nineteen canteen. Must be in a shed.

Check the feel of the new chain in the sprocket teeth, if it's a bit slack or the teeth are starting to become hooked, then it's new sprockets I'm afraid. If the links of the chain are snug in the teeth, then leave it until next time.

Unless of course you're thinking of 120mph+ frequently and the thought of a jumped chain at that speed terrifies you (it used to do me), in which case play safe.

A lot of this thinking relates in a different way to certain types of bike.

If you have an off-road machine like a trials bike or a green-laner then you will get away with replacing those components in what ever order suits you with no problems.

Once you start involving motocross bikes,road bikes and especially sports bikes then you are really going against good advice if you do not replace the components as a set. As stated before, the chain is the expensive part of the kit and the sprockets often cost as little as 15% of the chain.

The chain will wear and develop " tight spots " that really means it articulates badly at a certain point, with road biased bikes this constant juddering is taken up by the rubber mountings in the cush drive and will also translate into a specific wear pattern in the sprockets...getting more pronounced as the chain stretches.If you fit a new chain onto old sprockets, you are not getting an effective fit between components....the chain is not sitting perfectly between the teeth and can move around on the sprocket. This simply means that your new chain is going to wear, far faster than a normally maintained one would and you are having to replace them more often....you do not save money in the long run.

Just for interest.

I used a single set of chain and sprockets on a trans-Australia trip ( on a Suzuki DR650 ) and only needed to replace them on the last week of the trip...after 35,000km they were still good because of constantly maintaining the chain and keeping the correct tension.

I have also retired my shaft driven BMW ( BMW R100GSPD )and gone back to using a chain driven BMW ( BMW G650GS ) because a well looked after chain can last a long time, you can see what is wearing and how, it can be repaired ( spare Links ) .....and is a shitload easier to get hold of and fit than a complete shaft drive in the middle of nowhere ( as I found out )