Chain "Snapped"

Discussion in 'Bicycle Mechanics and Repairs' started by Sharky, 2 Apr 2019.

  1. Sharky

    Sharky Veteran

    Out at the weekend and the chain started skipping on the rear cassette when I put any significant pressure down. A few miles later, going up a hill - "snap" and the chain broke into three parts.

    I know chains don't snap. What happened was that one of the links, that I had previously joined together with a chain tool had bent a little and finally separated itself from the rivet. At the same time, the nearby quick link came undone and separated.

    So chain in three parts, with a bent outer plate. Fortunately, had my link remover with me and I was able to straighten the bent link and then re-joined the broken link. The quick link, which I almost lost in the gutter, I was able to find and rejoin and with the chain back in one piece, slowly rode back home.

    A new chain purchased and waiting to be fitted.

    Moral of the story - I was brought up just using a chain tool to cut and rejoin a chain and have always found the quick links fiddly to use. On my 1/8th & 3/32 chains, the chain tool works fine, but I think I will now just accept that for a 10 speed chain you have to use a quick link, although the chain tool will get you home if a roadside repair.
    raleighnut, Pat "5mph" and Smokin Joe like this.
  2. fossyant

    fossyant Ride It Like You Stole It!

    South Manchester
    Some new chains are very difficult or impossible to re-join now. Quick links.
    Sharky likes this.
  3. Yellow Saddle

    Yellow Saddle Veteran

    Loch side.
    Lesson learnt...sort of. It isn't the tool's fault but the type of chain. It helps to understand what's going on.

    On pre-9-speed chains the pins could be re-used because the peen (the little mushroomed head) didn't break off when the rivet was removed. These chains are usually just peened on two opposing sides of the rivet/pin end. It is distinctive in its looks.

    On newer chains the peen is very thin and right around the pin. This peen breaks off. Although it is subtle and most people don't see it, there are signs. The peen separates completely and settles on the chain tool's pin. You can see it in the photo below. The reason for that is to make the sideplate flatter and not have the peen protrude. This is achieved by countersinking the hole in the sideplate and then peening the pin to fill that hole but not protrude. On 8-speed chains the pin protrudes. You can feel it if you run your hand over the chain.

    Without the mushroom head to keep the pin in when the chain is flexed sideways. a refitted pin quickly allows the chain to burst open and break. If this happens in the wrong direction, the sideplate catches on the RD cage and rips it out of the frame. You are lucky if it happens on the "downwind" side and shaves past the cage.

    Peen on Chain Braker Pin.jpg

    Those little rings around the chain breaker pin are the broken-off peens from the chain pin.

    Peens on Pin 3.jpg

    For those without their reading glasses this morning.

    Peening Differences Between 11 and single-speed.jpg

    This is an exaggerated difference. It is a single-speed chain next to an 11-speed chain. It serves to show the difference, but in reality 8-speed chains aren't as aggressively peened as the chain in this photo.

    This is an 8-speed chain. Notice the partial peening. With this type of chain you can remove the pin and re-insert if it you have the skill. This peen will not break off.

    Pins Various.jpg

    This photo shows various full-peened pins. The bullet is just for insertion, look at the ridged pin itself. Notice how small and subtle the peen is. This breaks off upon insertion (except when a ramped inserter like in the photo is used to push it in.

    Chamfer vs no chamfer.jpg

    This photo shows the countersink/chamfer on a 9-speed chain (silver) vs a singlespeed above it.

    Worn vs new Pin.jpg

    Notice the broken peens.

    In summary then, from 9-speed up you cannot re-use a chain pin. It will be damaged and come apart when shifting. Surprisingly you can sometimes use such a damaged chain for a very long time before it strikes the lottery and the weak link appears at the weak point where it breaks. That weak point is the cross-over between two sprockets during a full-power gearchange. You have a 1-in-114 change that it will happen to that weak link.
    Last edited: 2 Apr 2019
  4. OP

    Sharky Veteran

    ^^^^^^ Thanks. Very informative.
    lane and Yellow Saddle like this.
  5. fossyant

    fossyant Ride It Like You Stole It!

    South Manchester
    Do you have these articles all ready to cut and paste @Yellow Saddle.

    Always very detailed.
    lane and mickle like this.
  6. Spiderweb

    Spiderweb Not So Special One

    North Yorkshire
    I wish @Yellow Saddle was local to me, I would have him advise & maintain my fleet in a heartbeat :smile:
    lane and meta lon like this.
  7. Crackle

    Crackle Squatter

    I had a 7 speed do similar. It began rattling in certain gears and I thought it was dérailleur adjustment but I couldn't tune it out. Then it just snapped going up an incline. The third time on that bike which is the only bike I've ever snapped chains on. I might send it to Yellow Saddle for a full analysis.
    Pat "5mph" and Sharky like this.
  8. Yellow Saddle

    Yellow Saddle Veteran

    Loch side.
    In this case, I had them ready because I wrote a book on chains. I have the photos on file and text in my head. I have a book on brakes and tyres (from a frictional point of view) at the publishers at present) and one on wheelbuilding in the making. For all of these I have collected photos and small experiences/anectdotes over a period of many years and kept them in separate files with keywords associated to them. Over the years I meticulously took macro photos and documented the cases and background.
    I also have a file on bicycle bearings but that one will not be turned into a book. These things are too esoteric to sell copies in any significant numbers.
  9. Smokin Joe

    Smokin Joe Legendary Member

    The mechanic in my LBS
    Exactly what happened to me with a nine speed. I'd originally cut the chain too short and added a link, which is where it broke. I've always used either a quick link or a Shimano chain pin since then.
    Sharky likes this.
  10. meta lon

    meta lon Guru

    He is local, you just need to like a little ride out... Few days sort of thing:smile: Tour De Bike Service:okay:
  11. Crackle

    Crackle Squatter

    The first time I'd done similar on a Shimano chain. After that I used quicklinks on KMC chains. I've no idea why it's broken twice since. Could be hamfisted usage. Once was mtn biking and the 2nd loaded touring, which was the rattling forewarning. Which reminds me I need to replace it as it's now too short and I no longer trust my own joins with chain tools for long term use.
  12. I’ve had a couple of instances when I’ve ended up with a Pringled link, and had to do a roadside repair. It’s one reason I’m very careful not to overdo the shortening of a new chain, if it needs adjusting. I always use quick links now, they cost very little and are easy to carry, I’ve just got to remember to check I’ve got the correct link, for the correct bike, as I’ve got a mixture of 9, 10, and 11 speed drivetrains. Some are interchangeable, some aren’t.
  13. SkipdiverJohn

    SkipdiverJohn Über Member

    When I see all this maintenance aggro concerning 10 & 11 speed stuff, plus compatibility issues etc, it just confirms in my mind that I was right to deliberately avoid the rear sprocket count arms race and stick with 5/6/7 speed set-ups, which seem to be inherently more durable and less hassle all round.
    Not to mention cheaper to maintain, as I bought a couple of replacement Shimano HG40 chains on special offer the other day for under £6 each as part of a larger purchase when including a discount voucher code from Chain Reaction.
    raleighnut likes this.
  14. Rusty Nails

    Rusty Nails We remember

    Here and there
    I will remember not to argue with you about any technical bike stuff In future!
  15. rogerzilla

    rogerzilla Guru

    Depressingly, most chains are peened to some extent these days, even most 1/8" chains. They look like Yellow Saddle's photo of the 8-speed chain above. I don"t use a chain tool to rejoin fixie chains any more - I use one of the old-fashioned 3-piece master links (which I have to buy separately, since new chains usually come with a non-reusable 2-piece joining link). The manufacturers probably do it to increase security of the pins, but it has the opposite effect if you break and rejoin the chain, the pin is no longer a tight fit in one side plate.
    Last edited: 2 Apr 2019
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