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Chain slipping on rear cogs

shoulder_of_orionshoulder_of_orion Posts: 529
edited March 2009 in The workshop
I bought a brand new Trek 1.5 which I picked up on Tuesday (24/02) and have been riding it to and from work since and have put roughly 60 miles on it.

This morning on my way in to work, for no appranetly reason, shortly after leaving a junction, the gears started slipping.

It stays in one gear for a couple of seconds and then slips in to the next smallest cog on the cassette. It then slips back to the original gear after a couple more seconds. It definitely does not matter whether I am on the large or small front ring and it also seems to happen whichever rear gear I am in although I think it is worse in some than others.

I am sure it is something simple to do with the rear Tiagra derailler. I can take it to me LBS in the morning but would like to get it solved for the pedal home if at all possible.

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  • AnonymousAnonymous Posts: 28,799
    I bought a brand new Trek 1.5 which I picked up on Tuesday (24/02) and have been riding it to and from work since and have put roughly 60 miles on it.

    This morning on my way in to work, for no appranetly reason, shortly after leaving a junction, the gears started slipping.

    It stays in one gear for a couple of seconds and then slips in to the next smallest cog on the cassette. It then slips back to the original gear after a couple more seconds. It definitely does not matter whether I am on the large or small front ring and it also seems to happen whichever rear gear I am in although I think it is worse in some than others.

    I am sure it is something simple to do with the rear Tiagra derailler. I can take it to me LBS in the morning but would like to get it solved for the pedal home if at all possible.

    Have your tried turning your derailuer screws? same happend to me....if it's slipping into the high gear then look for the screw with 'H' on it, righty tighty, lefty loosey...

    or take it to the bike shop you got it and ask them to do it.. they should if they are half decent. good luck
  • Don't mess with the H and L screws!!!! These are to allow the chain to run to the high and low cogs , if you adjust these it could make the rear mech go in to the spokes jump the chain over the smallest cog.

    It looks like the cable has stretched - that's all.

    You just need to turn the barrel adjuster by the rear mech, just small amounts maybe 1/4 turn at a time. Turn the pedals , shift the lever, and adjust the barrel adjuster at the same time (easier done in a bike stand or upside down! As the gear shifts it makes a noise if it doesn't go into gear, as yu turn the barrel adjuster the noise gets louder until it drops into the next cog. Shift all the way up and down the gears until you have silent running!

    A better explanation here -http://www.parktool.com/repair/readhowto.asp?id=64 and look for index setting. Good luck :D
  • Soul BoySoul Boy Posts: 359
    Hey,

    Was in the process of writing a longish response, but basically what Bikefotos said cable stretch sounds like the cause.

    Good luck
  • Thanks a lot for the advice guys - I have just been in the company car-park struggling with it for the past half hour. I even printed out the instructions on this page and from the parktool site.

    No amount of twiddling the barrel adjuster seemed to help that much. I did think I had solved it at one point and started riding round the car park - but no joy!

    Also upon closer inspection I realised my initial description may not have been completely accurate. It is not slipping gears from one cog to another - the rear mech is kind of "jumping" causing the same sound you get when a gear slips and it feels like that when peddaling along.

    Also I noticed that the gears will not shift down into the smallest two cogs. I am not sure if it has been like that since I got it or not.

    Maybe it is the H & L screws after all?? Or maybe a combination of cable stetch and somethingb else?

    I think I might just have to pootle home tonight and take it back to the shop I got it from in the morning. But ideally would like to solve it so I have a normal ride home.
  • AnonymousAnonymous Posts: 28,799
    Thanks a lot for the advice guys - I have just been in the company car-park struggling with it for the past half hour. I even printed out the instructions on this page and from the parktool site.

    No amount of twiddling the barrel adjuster seemed to help that much. I did think I had solved it at one point and started riding round the car park - but no joy!

    Also upon closer inspection I realised my initial description may not have been completely accurate. It is not slipping gears from one cog to another - the rear mech is kind of "jumping" causing the same sound you get when a gear slips and it feels like that when peddaling along.

    Also I noticed that the gears will not shift down into the smallest two cogs. I am not sure if it has been like that since I got it or not.

    Maybe it is the H & L screws after all?? Or maybe a combination of cable stetch and somethingb else?

    I think I might just have to pootle home tonight and take it back to the shop I got it from in the morning. But ideally would like to solve it so I have a normal ride home.

    yeah man, best be is to take it into the shop.. I dont wanna be cut down in a blaze of bad advice again ;) (p.s that was a joke guys..lol)

    same thing happend to me,, i wouldn't go into the smallest rear cog,, I turned the H screw a little to the right and hey presto chango its works... however I've also gotten myself into a right f**k up before with those screws, so best get someone to show you what to do in the shop..:)

    good luck man... hope it works for ya

    G
  • rally200rally200 Posts: 646
    Step away from the H & L screws - if you were able to get top & bottom gears when you first picked up the bike then they are probably set OK - they only need doing once, and I'd assume your lbs would have done it. as the other guys said it's very likely cable stretch. it sounds like you've adjusted the cable adjuster too far the wrong way (ie too loose) if you can get to your lbs they should be happy to show you how to adjust it
  • VividVivid Posts: 267
    It will take less than a minute for any bike mechanic to sort it out for you so just pop it down.
  • Thanks all for the advice.

    For the sake of closure, I will complete this story. I took it to the LBS this morning and they sorted it out. It is a bit annoying as they don't open till 9am and close at 6 so for me to get the bike in I have to lose at least an hour from work (my commutle is an hour). I could not make it on saturday.

    The problem was in fact a stiff link in the chain which was causing the chain to jump. My changes to the barrel adjuster had no effect other than to tighten the cable to near breaking point. The mechanic showed me how to check for this and how to index the gears properly (front and rear) and advised that if the barrel adjuster had to move more than a certain amount, I would be better off pulling more cable through.
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