How do I know if my chainrings need replacing?

rodgers73

I've got a chain wear tool so I can check that and my cassette is fairly new so I'm happy with that too, but I've no idea about my chainrings.

Is there a wear measuring device or something??

rodgers73

I have a 2010 bike with a triple chainset.

Its a Shimano FC-R453 Octalink with a 30/39/50 set of rings on it.

It's been used quite a lot in the time I've had it. It's on its second chain and cassette.

Can you even buy new rings for these??

Mindermast

In German, it is called "shark-fin-tooth" (translated). When the teeth of the chainrings look like the back fin of a shark, the chainring should have been replaced a while ago. The same, when the chain starts sliding on the chain ring, which is because of this shark-fin shape. Fortunately, chain rings have quite a long live span, compared to chain and cassettes.

Oh, of course you can buy new chainrings for that crankset. And you don't even need to buy Shimano chainrings, what matters is the distance of the mounting holes. With Shimano chainrings, shifting might be a bit smoother only.

Somewhere I heard, that chainrings survive up to three cassettes, which survive up to three chains. It probably depends on many factors. By the way, worn out chains decrease the live span of cassettes and chainrings a lot.

wishitwasallflat

I've heard at least 10k miles so for me 9 chains and 3 cassettes would fit with that kind of all weather mileage but as with all wear it depends on weather and riding style.

rodgers73

Ah, thanks. It sounds like I'm quite some way away from replacement then.

I have thought about stripping the rings off the crank for better cleaning but have no idea how to unfasten the bolts! Looks like an allen/hex key bolt but I'm not sure if a torque wrench is needed for the re-tightening.

turnerjohn

one test.....get the chain in the ring, pinch the chain from the front of the bike and try to pull it off the ring, if you can clear the links with the front tooth they need replacing.....bit hit and miss but does give an indication

rolf_f

Mindermast wrote:

In German, it is called "shark-fin-tooth" (translated). When the teeth of the chainrings look like the back fin of a shark, the chainring should have been replaced a while ago.

I'm at this point myself but not convinced of the above.

Order of wear = chain - cassette - chainring.

If you leave a chain on too long it causes premature wear to the cassette (ie shark fin on the smaller sprockets) - therefore, it is important to change the chain before it gets too worn. Swapping chains maximises cassette life but the point is that you still only need to actually replace the cassette after the problem (ie slipping) has first occured.

At the same time, the chainrings are also wearing but much more slowly due to them being larger than the cassette sprockets. But similarly, there is no point changing them because the teeth are shark finned unless it is causing a problem. I've not noticed any problems yet with my chainrings despite using new and old chains on them but they are both clearly well worn.

Incidentally, the small ring will wear first. I managed to source one of those but it is mad how expensive replacement rings retail at. A Campag 50 is over £100. On that basis, the chainrings are the drivetrain components that you leave on longest even if that does cost some additional wear elsewhere.

Monty Dog

Chainring teeth when very worn are almost pointed and have a hooked profile due to wear on one side - due to the silly price of replacement rings, I often just buy a new chainset. A good quality chainring will last well over 25,000 miles or 10,000 if SRAM as they appear to be softer than cheese.

schweiz

I go through about four chains per cassette, and four or five cassettes per chain ring so that's up to 40,000 km which is about the same as Monty Dog experiences.

If you have to pay full RRP for the chain ring, then as Monty Dog says, a new chanset often seems more appealing. If you hunt around though you can pick chain rings up cheaply. I put a new chain, cassette and rings on a mates hack MTB last summer. He just wanted it to work and IIRC the Shimano rings (LX?) were about £35 for all 3, I gave him a 9-speed KMC chain I had lying around and a new Shimano cassette was 20 quid. I fitted it for a bottle of single malt whisky and he saved a fortune on what the LBS had quoted!