View Full Version : Chain jumping
19th July 2009, 9:14 AM
Since beginning road riding 3 years ago I have maintained my bike as best I can with my limited knowledge.I pay particular attention to keeping it clean as well.Up until now I havent really encountered any problems.Today however I started getting out of the saddle and sprinting against a cycling partner of mine.I noticed that by exerting a lot more weight through the pedals than usual my chain slipped and jumped.This happened on several occasions.I wonder if any one can offer an explanation as to why this may be happening?Also I am going to put my bike in for a service. What should I expect to be done to my bike in a service?Thanks
Pete Appleby 3
19th July 2009, 10:24 AM
The usual cause is worn chain and cassette, so I would budget for that plus labour about £50 in parts,As for a service i would expect that the shop would check brakes, headset, clean and adjust brake and gear cables(replace if needed) check the drive train for wear and tear advise whats needed in this case probably new chain and rear sprockets, check bottom bracket ,realign front and rear mech, check chain ring and cranks, check pedals, check wheels and tyresand report on the general condition of the bike
Mike the bike
19th July 2009, 3:24 PM
As Pete says, it's likely to be the chain and some cassette cogs that are worn. But, depending on your mileage, after three years I'd expect to see some wear of the chain rings too.Although the shop should check this automatically on anything but a very basic service, I would ask them to give it the once-over. It would be a shame to ruin a new chain on knackered rings.
19th July 2009, 5:22 PM
Could be the tension on the rear derailleur has slackened off over time. Try tightening the cable by a quarter turn or so.
19th July 2009, 5:32 PM
Have you changed your chain in the 3 years you've had your bike?My money is on the chain and sprockets - and depending on the mileage, the chain rings as well!!! Not to worry, it's time for a service anyway and these things have to be replaced!!
Mike the bike
19th July 2009, 5:46 PM
To be honest Wizz, even if you need chain, cassette and chain rings, there's nothing to prevent you from changing them yourself and saving a load of dosh.Parker's ( or any number of others ) will flog you the bits from their website at far cheaper prices than your LBS. Just have a read of the Park Tools web instructions and get stuck in. Even if you've got to buy a cassette tool and chain whip, you'll still be quids-in.
20th July 2009, 4:59 PM
Many thanks for your advice. I'v checked the teeth on cassette and sprocket and visually all appears well.I would estimate the mileage done so far would be about 1700 miles.Do you think it's still as suggested or maybe something else.Cheers
20th July 2009, 5:26 PM
You won't necessarily see the wear. Also, the chain may have stretched. However, 1700 miles isn't much, so I'd suspect the derailleur needs a bit of alignment. Turn the pedals backwards quite fast by hand. If it jumps all over the place, that's the problem!
20th July 2009, 5:31 PM
It's very difficult to judge visually although sometimes the teeth on the sprockets can develop faint hooks on the rear surface. In any event, it is very unlikely that you would experience any significant chain wear in that distance unless it was very cheap. It does remain high on the list of differential diagnoses but cogs and chain tend to wear together so the problem doesn't usually arise until you change one or the other especially with the distance you've done, whats more the chain would only slip on the sprocket its on (i.e not jump off) and usually only on the smallest. So does it rattle at any other time and are your changes clean or do you have to fiddle with the levers to get a clean change? If these are the case then the rear mech may simply need adjusting. Failing that it could be a faulty gear lever but again it would tend to jump gears not just slip on the same cog.
Bill Day 2
21st July 2009, 11:44 AM
I'd put money on it just needing adjustment of your rear derailleur, try turning the barrel adjuser a quarter turn as suggested above. Give it a ride and see, might need another turn or two before it stops jumping, but dont turn too far or you'll start skipping gears as the tension will be too tight.You can give your chain a rough check for stretch by measuring it when its taut - get a 12" rule and lay it on the chain, should be exactly 12" between 2 rivets. 12 1/8 means you need a new chain (and cassette). Bike shop can confirm this with a special tool but this will give you the idea. I'd also learn how to do maintenance youself, its cheaper and much more satisfying and you'll take much greater care to get it right than any shop ever will!
21st July 2009, 2:24 PM
Many thanks everyone for your advice. And yes I am going to invest in a good maintenance book and try some stuff myself. I think I will opt for the Park Tools Blue Book.Cheers
29th July 2009, 8:41 AM
Guys, your predictions pretty much appear to have been correct.Visited the LBS and apparently my chain has stretched and cassette worn. They are going to replace both with the same Shimano 105 £80 , thats £55 cassette, £20 chain £5 labour. I have taken your advice and ordered a maintenance book ( Park Tool blue book 2 ) I am going to have a go next time myself! Surely its not rocket science ! ( famous last words ).Guys, What tools should I invest in for this type of maintenance. To date I have a good selection of normal DIY tools and enough to fix a puncture ?Also out of curiosity in mileage terms , how long / far would you expect a chain and cassette to last ?Cheers.
29th July 2009, 2:29 PM
Buy tools as you go along sufficient to complete the job in hand and you won't feel the cost of purchase too much. A comprehensive set of Allen keys makes a good start.For chain and cassette replacement you'll need a chain tool, chain whip to hold the cassette and lockring tool to get that part off.
29th July 2009, 5:07 PM
Sounds wrong for 1700 miles though...
Mike the bike
29th July 2009, 5:59 PM
Yes it does sound strange. I ride every working day, winter salt and summer rain, and expect to get 5000miles from very much cheaper components.But so much depends on the level of maintenance, and I wash and lube my chain/cassette every week without fail.
29th July 2009, 6:54 PM
Yes it does sound strange. I ride every working day, winter salt and summer rain, and expect to get 5000miles from very much cheaper components.But so much depends on the level of maintenance, and I wash and lube my chain/cassette every week without fail. And your'e not a LBS out to take advantage of someone with little knowledge of bikes, and make a fast buck.........................................Did I say that out loud?dave