Why do cassettes wear quicker than chain rings?

Haynes
Haynes Posts: 670
edited April 2008 in Workshop
Just like the title says. Chain rings have a lot more teeth but there is only 2 of them, yet they can outlast a good few chains and cassettes, why is that?
<hr><font>The trick is not MINDING that it hurts.</font>

Comments

  • andrewgturnbull
    andrewgturnbull Posts: 3,861
    Hi there.

    On a 53 teeth chainring, approx 26 of the teeth will be engaged at any one time, wheras on a 12 tooth cog, less than 5 teeth will be engaged. Hence > 5 times the stress on each tooth?

    Just a guess. I'd guess also that the relationship between wear and stress is not a linear one either.

    Also the chain is changed between the cogs at the back far more often than you'll use your front derailleur.

    Cheers, Andy
    http://www.andyturnbull.co.uk
    http://www.stirlingtri.co.uk
  • Monty Dog
    Monty Dog Posts: 20,614
    Because of the amount of load exerted through each tooth - the smaller diameter means that a sprocket takes the load over 2-3 teeth whereas the load on a chainring will be distributed over a larger number of teeth.
    Make mine an Italian, with Campagnolo on the side..
  • laurensdad
    laurensdad Posts: 46
    What Andy and Monty said.
  • Stuck on a Giant
    Stuck on a Giant Posts: 256
    And the rear wheel goes round 4-5 times more than the chainrings, so more stress more times.
  • imaca
    imaca Posts: 3
    If you look at an engineering handbook, the tables for chain cog selection will tell you small rear bike cogs are by definition too small. Chains and cogs just ar'nt meant be treated like that - there are too few teeth engaging and the change in angle between links is too great. The high level of wear is a compromise taken because otherwise casettes, chainrings and derailliers would be impractically big.

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