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My chain fell between the cassette and the spokes while riding, and it destroyed my rear wheel. I know I'll have to replace the wheel, but can I keep the cassette and the chain? There is no visible damage on either.

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    Why replace the wheel? Have the damaged or broken spokes replaced and the wheel trued.
    – Carel
    May 9, 2017 at 9:54
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    The most important thing is to properly adjust your rear derailer. After that, get a spoke guard. (Yeah, some folks think they're dorky looking, but they have a purpose, as you've found.) May 9, 2017 at 12:03
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    Take the wheel to a shop. They should be able to check what spokes are damaged if any, true it up again, and make it ridable again.
    – Batman
    May 9, 2017 at 13:19
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    Thank you for your suggestions, but the wheel was beyond repair. One spoke got ripped out of the rim and mangled itself around the hub. 2-3 other spokes pulled visible dents in the rim, another 3 broke. All spokes on the right side got bent at the center. I salvaged the hub and the left side spokes, but the easiest (and if I count labor time or repair costs, the cheapest) option was a new wheel.
    – matega
    May 9, 2017 at 14:11

1 Answer 1

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Yes - I've suffered the same event when the chain jumps over the cassette and you keep pedalling.

In my case I kept trying to pedal, and the chain chewed into about 9 spokes right at the elbow. I probably damaged the chain a bit too. Surprisingly, the cassette seemed OK.


The fix options

  1. replace the rear wheel - this is the most expensive, but gives you peace of mind and a warranty. I couldn't afford this.
  2. replace the damaged spokes. Spokes are between $1 and $3 unless you have weird ones. You will need a "spoke nipple tool" and whatever tool is needed to remove your cassette/freewheel from the hub of the wheel. Simply replace the most-damaged spokes one at a time, duplicating the under/over pattern. Once they're replaced, use the nipple tool to true the wheel.
  3. do nothing and wait for the spokes to break. Depending on the level of damage you might be able to ride fine for a long time as-is.

The prevention

The chain jumped over the largest cog on your cassette. This is because the low limit screw is not set right on the rear derailleur, and it allowed the chain to go too far.

https://farm6.staticflickr.com/5219/14089535263_a82bdff6e2_o.jpg

Its highly possible your RD was "plinking" into the spokes as well, which is very close to catching a spoke with the RD and then its all badness.

The other prevention is to use a Spoke Protector, which is a clip-on ring that sits between the cassette and the spokes.

enter image description here

Normally made from clear plastic on new bikes, they were steel or aluminium on older bikes. Old plastic ones go brittle and then crack and fall off. These are also known as dork disks and while they do their job, they also offer a large flat area to side winds.

There's nothing wrong with fitting one - should be about as much as a spoke or two, available from your LBS.

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  • Personally I replaced the four worst bitten up spokes, and then rode that wheel for a couple more years. I believe its hanging in my pile of spare wheels now, still with some slightly munchy spokes surrounding 4 nice shiny ones.
    – Criggie
    May 9, 2017 at 10:54
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    Thank you for the detailed answer! Unfortunately, a spoke got ripped out of the rim and another 2-3 pulled visible dents into the rim, and all right side spokes got really bent, so that rim is beyond repair. I adjusted the real derailer more carefully and replaced the wheel. I'll also consider a spoke protector.
    – matega
    May 9, 2017 at 14:18
  • @matega ok bother - spokes pulled through the rim would kill the rim for riding. You're now up for a replacement rim and at least replacement spokes for any that are damaged. You could replace all the spokes, but that gets expensive. Its likely your axle, hub, cassette/freehub/freewheel are all okay and can be reused. Inspect the chain closely and if its damaged, or approching stretched then replace it as well.
    – Criggie
    May 9, 2017 at 20:11

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