Skipping Front Chainring

MartinGT
MartinGT Posts: 475
edited July 2014 in Workshop
Evening Guys

Yesterday I changed my chain and cassette and gear cables on one of my bikes. I have done this countless times on road and MTB's and no problems.

I went out this afternoon and as soon as I went to put any force of note through the cranks it would skip in the big ring. If I kept a constant pressure I was fine. I stood up on a couple of climbs and it skipped.

Everything was fine when I dropped to the smaller chainring. I could stand and put force through it no worries. As soon as I was in the bigger chainring, it skipped at the front.

Now, I got back and had a look at the front chainring and there are some signs of wear in the chainring. I checked the chain for any stiff links, nothing but I would expect slipping on the cassette and not the actual front chainring.

Now, I assume, its a worn chainring. But is there anything I have missed? Its a 105 chainring. I have found the one I want (if thats the answer) but also see 110 or 130. What is this referring to?

Thanks for the help.

Comments

  • sungod
    sungod Posts: 17,350
    110bcd/130bcd refers to the 'bolt circle diameter' of the chainring bolts

    for a 5-bolt system, measure centre to centre of a pair of adjacent bolts

    110bcd will be c. 65mm

    130bcd will be c. 76mm
    my bike - faster than god's and twice as shiny
  • Matthewfalle
    Matthewfalle Posts: 17,380
    Sounds like a worn chainring that needs replacing.
    Postby team47b » Sun Jun 28, 2015 11:53 am

    De Sisti wrote:
    This is one of the silliest threads I've come across. :lol:

    Recognition at last Matthew, well done!, a justified honour :D
    smithy21 wrote:

    He's right you know.
  • lapavoni10
    lapavoni10 Posts: 146
    Have you routed the chain correctly through the rear mech? If you have run the chain over one of the bars between the side plates, you may not be getting enough wraparound on the cassette when in the big ring?
  • MartinGT
    MartinGT Posts: 475
    Thanks for the replies guys.

    Yes, I have checked the chain through the rear mech, plus if I had done that it would skip at more regular intervals and not just when I put a larger amount of power through the cranks.

    I have checked the front chainring this morning and can confirm, that a few teeth are very worn :oops:

    New ring on order.

    Thanks again
  • davecara
    davecara Posts: 104
    I'd check the 'worn' teeth against a new ring if you can. Not all of them should be the same height, you'll notice a drop in tooth height on some rings where they're designed to 'pick up' the chain when shifting

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