Chain ring wear

02gf74
02gf74 Posts: 1,171
edited June 2018 in MTB general
There may be a simple explanation.

Chainrings are generally aluminium alloy whereas the cassette sprockets are steel.

Generally riding a bike means charging gear on the cassette more frequently than say on the front. This means wear is shared across the sprockets.


When a badly worn chain is replaced, a new chain will jump on the rear first and if extremely worn, on the chainrings.

Why is that, the sprockets are of harder metal plus see wear shared between them due to gear changes (note chainrings used to have more teeth, middle and large to share the wear, but with 32t single with 11-42 cassette that no longer is the case.)

Comments

  • steve_sordy
    steve_sordy Posts: 2,453
    02GF74 wrote:
    .................

    Generally riding a bike means charging gear on the cassette more frequently than say on the front. This means wear is shared across the sprockets.

    .................


    You answered your own question. :)
  • 02gf74
    02gf74 Posts: 1,171
    steve_sordy wrote:
    02GF74 wrote:
    .................

    Generally riding a bike means charging gear on the cassette more frequently than say on the front. This means wear is shared across the sprockets.

    .................


    You answered your own question. :)

    Not at all.

    Lets say riding a bike produces X amount of wear. (units I won't specify).

    At the rear it is shared by the sprockets so for 9 speed cassette, each sprocket wears by X/9.

    At the front each chasing wears by X/3.

    Since /3 is more than /9, the chain rings should be more worn.

    Also sprockets are of harder metal.
    Obviously the number of teeth come into effect so it is not as simple as that.
  • FishFish
    FishFish Posts: 2,152
    Good point.

    Or if the wear is caused by a tooth interacting with the chain. On a Front there are say 34 T and the average gear at the back has 15 T then one link interacts with a specified tooth at the back 32/15 times.

    You can modify this if you want the leading edge of the chainring (the front half) to be in contact with the chain - say 17 T and on the cassette the trailing third say 5 T - actually that accentuates the wear on the back.
    ...take your pickelf on your holibobs.... :D

    jeez :roll:
  • steve_sordy
    steve_sordy Posts: 2,453
    You need to take into account the relative numbers of teeth.

    And the amount of use in each gear, especially the front rings. I was always wearing out the granny, hardly ever had to replace the other rings (when I had a 3x).

    Another factor is the number of teeth in contact with the chain, as that shares the load. It is not an exact ratio with the number of teeth in contact because the load is not evenly shared across all teeth in contact with the chain. Chain wear reduces the number of teeth taking a high load which accelerates wear quite markedly. This is another reason why steel teeth last longer than aluminium ones, they are just more resistant to high load abrasion.

    The degree of overlap varies as well. The front rings have pretty much a 180 degree wrap, whereas the cassette gears don't.

    The above is not a definitive argument for every bike, because they all vary, from 6-speed to 12 speed and from 3x to 1x. And then there's the elliptical chain rings!

    Not all cassettes are made from steel. The latest Shimano 12-speed comes wit steel small gears, titanium middle gears and aluminium large gears. I'm sure that if I go look at the cassettes in my garage that I will see they are not all steel.
  • 02gf74
    02gf74 Posts: 1,171
    steve_sordy wrote:

    Not all cassettes are made from steel. The latest Shimano 12-speed comes wit steel small gears, titanium middle gears and aluminium large gears. I'm sure that if I go look at the cassettes in my garage that I will see they are not all steel.

    Indeed, 9 speed xtr had largest 2 or 3 sprockets made from Ti, sram x01 and xx1 have alloy 42 sprocket.
  • mtbleague
    mtbleague Posts: 6
    To add to SS's point there is also riding style and terrain to take into account, on my 3 x 3x 9's....

    I personally apart from chain being worn, have found the lower on my rear sprockets seem to wear most dure to my climbing mostly on the middle ring on the front, then the big ring on the front due to my decending with the chain there (some impacts also wear it) I havce long since found that a steel/carbon middle ring suits me best and wears nearly as much as my rear, have never worn out a granny one yet. :o
  • billycool
    billycool Posts: 833
    You see - no simple answer.

    There are too many variables due to construction materials, number of gears, which ones are used most regularly, riding style etc.

    On my 3x9 HT set-up, I recently changed the cassette, chain and middle ring. I don't use the granny and the big ring is a my `downhill` gear, so it is usually under less stress and lasts much longer. My middle ring does more work and wears quicker.

    I don't look at my cassette in any detail, although I'm sure some parts of it may wear more than others. I know with my XT cassette I do have steel and alu gears.
    "Ride, crash, replace"
  • steve_sordy
    steve_sordy Posts: 2,453
    Cassette wear: look for hooking of the teeth and also "burrs" on the sides where material has been pushed from the tooth face where it belongs. Hooks can hang on to the chain, burrs can impede shifting. Neither are good to have.

    If you have a problem and can't get a replacement cassette, the burrs can be filed off, but you won't be able to fix the hooking. It's a bit of a fag, but I once filed off all the burrs on a cassette and made it last another month. In which time I'd bought another cassette and chain cheaply off the net and had them delivered, instead of paying a fortune from the LBS.

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