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I've got a fairly old Dawes Discovery 301 (not sure of the year); earlier today I took it to a shop to have a replacement bottom bracket fitted. I rode it 2 miles home, and noticed a slight intermittent skipping feel and noise from the chain which hadn't been there previously. I didn't stop to investigate until I got home as both the noise and the feel seemed "minor" (learning point for me there). When I did, I found that one link on the chain had one side detached with the pin sticking partway out; the eyelet on the detached side is quite bent. I'd attach a photo but my camera has apparently stopped working. It's not an easy-open link or anything else fancy.

I'm concluding that the chain's been re-fitted badly. I plan on returning to the bike shop (not riding the bike!) and asking for a new chain to be fitted free of charge. I can clearly see the lettering on the links saying it's a KMC Z40, which I'm guessing is discontinued because I don't get any relevant-looking hits on a search. It's on a Shimano CS-HG30-81 cassette.

Questions:

1) Is my plan reasonable, or is it well-known for older chains not to re-attach well? I've measured the chain to look for lengthening due to wear (per http://www.bicyclinglife.com/HowTo/ChangeAChain.htm) and I believe it's at most 1/16th out at the 12-inch mark, so I'd say it's worn but not excessively so. The cassette doesn't "look" terribly worn either. I acquired the bike recently-ish from a relative so can't be sure about its previous use history, but I don't think it was massively punished.

2a) If 1) answers "yes", is there any specific type of chain I need to ask for? I ride on roads most days and on light off-road trails on occasional days.

2b) If 1) answers "no", please can you advise on an alternative strategy? I recognise this is subjective and calls for opinions, but I'd be interested to see what others think is reasonable in this situation.

I've used this shop before and always believed them to be reputable.

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    Take it back, ask for a repair (thats reasonable), expecting a new chain for free is unreasonable as its a trivial repair. If they really are are reputable, they will repair the chain at no cost (or maybe the cost of a quicklink which I would recommmend).
    – mattnz
    Nov 8, 2013 at 1:07
  • Indeed, having a LBS that you trust and can openly talk with the mechanics is at least as valuable as being a member of an online community with so many competent riders and mechanics!
    – Vorac
    Nov 8, 2013 at 7:55

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@Alexander is right, there is no need to break a chain when you replace a bottom bracket. So your hypothesis doesn't make complete sense, unless maybe they were doing other stuff to the bike?

So if you do take the bike back to the shop, odds are that that's their response.

I know if I got myself a new (second-hand) bike, I'd think about replacing the chain almost automatically. Same as something like brake pads. Just so you know where its come from, plus they're cheap enough its almost a no-brainer.

By the looks of that cassette its an 8-speed, so you just need an 8-speed chain (e.g. http://www.kmcchain.eu/?en/products/multiple_speed/8_speed_derailleur/). Really common, any bike shop will have one. If you decide to buy off the web and fit it yourself (easy enough, just need a chain tool, which is an invaluable tool to have in any case), actually KMC is a decent brand to go for anyway.

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    +1: Note that a new chain now will extend the life of the cluster and chanrings.
    – mattnz
    Nov 8, 2013 at 1:09
  • Where I'm live the chain is not so cheap :)
    – Alexander
    Nov 8, 2013 at 7:08
  • @Alexander, depends on the chain. SLX chains are several times more expensive than simple 7-speed chains. By the way, it is possible (while not recommended) to run a 7-speed dirt-cheep chain on an 8-speed drivetrain (tried it, worked reasonably, the chain cost 7.50 BGN).
    – Vorac
    Nov 8, 2013 at 7:53
  • @Alexander - its all relative I suppose. But the OP has just been to his LBS, bought a new bottom bracket and paid to have it fitted. Compared to that, I suspect a new chain would count as cheap!
    – PeteH
    Nov 8, 2013 at 12:57
  • A chain extending the life of the cluster and chainrings depends on how worn they are already - putting a new chain on a worn cluster will first skip, then quickly wear the chain down to the cluster's wear level and then you've wasted a new chain. That being said, a 7 speed chain and 8 speed chain are pretty much the same thing (and in most places, pretty cheap), so depending on wear levels you may just replace a few parts.
    – Batman
    Nov 8, 2013 at 19:07
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There is no need to detach the chain to change BB. I don't believe that the shop will give you warranty in this case. Therefor the answer question 1 is no.
There is no need to replace the whole chain. Usually replace of only 2-4 links will solve the problem.

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  • While it's not necessary to detach the chain, I could see it being done. To change out the bottom bracket, you need to remove the crank set. Once you remove the crank set, the chain will just hang down from the front derailleur. Removing the chain would stop it from getting it the way when trying to work. Definitely not necessary, but I could see it being convenient. And 7-8 speed chains don't have many problems with opening the links once in a while.
    – Kibbee
    Nov 8, 2013 at 15:30
  • As a shop worker I don't see any problem to work with BB while the chain is attached. If you turn the bike up-down, the chain will lay lower enough to work with BB.
    – Alexander
    Nov 9, 2013 at 18:57

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