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Chainring teeth, should they look like this?

andy9964andy9964 Posts: 930
edited July 2013 in Workshop
I have a 2013 Cannondale Synapse with a Sora triple chainring.
It's about 8 weeks and 500 miles old.
I've kept it clean and lubricated in this time, and today I had the chain off so I could degrease everything properly.
While feeding the chain back on, I noticed some of the teeth on the big ring are of different sizes/flattened at the top. Most are pointed
There's probably about 4 or 5 like this, with seemingly no pattern i.e. every 10th tooth

Any ideas/suggestions

2013-07-14194345_zps3166be09.jpg

2013-07-14194501_zps6b25251a.jpg

Posts

  • MindermastMindermast Posts: 124
    Ok, I don't know. But if you look at the tooth right next to the very short one, it is a bit longer, but shorter than the others. This might be on purpose, to make it easier to move the chain from one ring to the other.

    I suppose, the chainrings are steel. Breaking the tip of a tooth would probably brake a bit more than just the tooth...
  • imposter2.0imposter2.0 Posts: 11,200
    normal.
  • anyuseranyuser Posts: 51
    Completely normal
  • andy9964andy9964 Posts: 930
    Aha, makes perfect sense now

    Thanks to both of you for the speedy replies
  • keef66keef66 Posts: 13,123
    They are made like that to help with shifting; the shorter teeth give the chain an opportunity to leave the bigger chainring when dropping to the smaller. Going in the other direction the ramps and pins on the inside of the chainring help pick the chain up and lift it onto the bigger ring where the shorter teeth let it engage. You'll notice the pins are just in front of the shorter teeth.
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