Drivetrain Wear - Thoughts

[groberts]

Just looking at my cassette, chainrings etc and would be grateful for you opinions. I have had the bike new since 2007 (2006 Dawes Audax) and have probably done +12,000 miles - see photos.

1. Tiagra Chainwheel - (a) is the wear of these teeth excessive and needs replacement? (b) every fourth or fifth tooth has a small notch worn at the base e.g.third form the right - what might be causing this?

2. Cassette - (a) is the wear shown OK or does it need replacement? (b) if renewed can I add say a couple of extra teeth on the lowest cogs without causing any gear problems?

3. Chain - (a) how many miles can you expect from a chain? (b) does this look knackered?

Thanks

[PW]

12,000 is well past life expired for the chain if you want to re-use the cassette. The chainrings are probably getting near terminal too.
Rule of thumb:-
Chain links are 1/2" centres between the middle of each pin when new. With use the joints get sloppy and the chain elongates, so the rollers don't drop in the centres or the sprocket tooth cutouts, instead they grind away the edges of the sprocket teeth, then eventually the same happens to the chainrings.
Measure the chain between pin centres when pulled tight. Use a steel rule/tape with inches and 1/16" graduations. A nominal foot length will expand to 12-1/16" when it's worn out. Scrap it and replace there should be no damage to the cassette or c/rings. If it expands beyond that limit the cassette will need replacing or the new chain will jump on the old worn teeth. If the chain expands to 12-1/8" over that nominal foot you can expect the chainrings to be similarly damaged.
Chain life varies according to how well it's cleaned and lubricated, and how often, and the area where it's ridden. Grit in the rollers will kill it quickly so clean it more often if you ride trails and towpaths. My 9 speed triples wear out an SRAM chain on average in around 2,000 m.

[jackg]

http://sheldonbrown.com/chains.html
Scroll down for wear.

[Trigger]

From your pictures I would say the cassette doesn't look* that bad, there's what looks like some wear to the larger few sprockets but the smaller ones look hardly used, do you spend most of the time in a lower gear? I wouldn't wan't to use it on a new chain though, so for the sake of the low cost of a replacement I'd change it.

Can't tell with the chain rings, the big ring usually doesn't wear as much as the middle, unless you're a flat lander that's always in the big ring.

* Depends how it rides, looks can be deceiving. Does it ride and shift ok?

[Vorpal]

Why do you ask? Is there a problem that you are trying to fix? If so, what? What made you notice or think about the wear?

[531colin]

Look at your cassette photo. The 3 or 4 smallest sprockets are unworn, I guess you don't use them.
The bigger sprockets teeth are a different shape, much more pointed...the chain has worn away at the side of the teeth it "pulls" at...ie the back...you can even see a "lip" where the wear is...its a good photo!
The natural history of all this is that the chain wears, and then the worn chain wears out the cassette. So your chain is scrap, and I think if you try to use a new chain on this cassette it will skip under pressure on the worn sprockets.
Chainrings are a different matter, the teeth at the top wear when you push down on the pedal, so you get 2 "patches" of wear separated by 2 "patches" showing less wear.
You need to compare tooth profiles of the different chainrings , at different points, to judge wear.
I think "road" rear mechs. will handle up to 28 teeth at the back, but check me on that, eg http://techdocs.shimano.com/techdocs/index.jsp

[niggle]

From your pictures I would say the cassette doesn't look* that bad, there's what looks like some wear to the larger few sprockets but the smaller ones look hardly used, do you spend most of the time in a lower gear? I wouldn't wan't to use it on a new chain though, so for the sake of the low cost of a replacement I'd change it.

Can't tell with the chain rings, the big ring usually doesn't wear as much as the middle, unless you're a flat lander that's always in the big ring.

* Depends how it rides, looks can be deceiving. Does it ride and shift ok?

Also looks to me like the larger sprockets are worn. At this point I would try a new chain but be expecting to have to buy a new cassette as well. I think the OP has more chance with the chainrings. Of course if the chainrings also will not work with a new chain, but all was working OK before, he might as well put the old stuff back on and run it until it actually stops working, then replace the whole lot at that stage.... I think the notches on the chainring teeth are there from new BTW and agree that the middle ring is the most likely to be suffering from wear.

[reohn2]

Looking at it I'd say the chain and cassette are scrap,the cassette won't stand another chain not after 12,000miles on the same chain,new chain and cassette required.
The little notch/chamfer on the chainring looks to be caused by gearchanging,when the chain is being unshipped from the big ring.If you notice theres also a similar one on the front of the teeth that is caused when the chain is changing up from the middle ring.The chainirngs in the photo don't look exessively worn to me and I'd be surprised if they wouldn't be OK with a new chain.
I find chainrings last atleast 20,000miles even on the tandem which takes a lot more torque than solos,but then again I never run them for that mileage on one chain,the best I can hope for a chain is 5,000mls solo and 2,500mls on't tandem,
I usually get three chains to the cassette which costwise for a solo is about the same or a little less than you've got out of one chain and cass'.The problem I have is that shifting isn't as crisp when a chain starts to get to its wear limits(the limits advised by PW)

[groberts]

Thanks everyone, that's very helpful and mostly confirms what I was thinking. I do use the lower sprockets most - particularly since a knee operation earlier this year.

Given my mileage, looking at the drivetrain after cleaning and reading this forum over a period of time, got me to thinking I might need to do something; I actually bought a new chain last year but hadn't installed it yet on the principal that the old one still worked OK. However, before somebody says so, preventative maintenance is also important.

[byegad]

If you fit a new chain and it skips on some or all of the front and/or rear rings then they are worn out too. I replaced the chain on a similar mileage bike I was giving to my sons better half and it skipped on most of the cassette rings. A new cassette later all was fine so the chain rings were still OK. Had they skipped, and I thought they might, then it was new chainrings too.

[john.will.wright]

If you're thinking of replacing everything then you might as well ride it until it is no longer usable. If it's not skipping you might as well just keep going, you won't go any faster with a new chain!