Broken spoke caused tyre to eat into paint

[Mr. Cow]

A few weeks ago I bust a spoke on my rear wheel. This caused the wheel to deform and the tyre to gouge a few layers of paint from the inside of the chain stay before I could stop in time. I'm not too bothered as it happened on my old commuter, I had the wheel repaired and cleaned up and put a clear patch of helicopter tape over the area.

If this had happened on my nice bike I'd be pretty gutted though. Is it normal for a broken spoke to cause that much damage? I suppose other than keeping a closer eye on tension there's not much can be done to avoid it?

 

[lostinthought]

It happens. It depends on tyre clearance and how many spokes. For older bikes with 36 spoke wheels, a broken spoke is generally an inconvenience to be fixed when there's time. For wheels with half as many spokes, a broken spoke might be ride-ending. Something similar applies to tyre width.

We've all done it though, and a bit of paint lost to rubbing tyres is just part of the history of a bike. No biggie, unless you leave it years and the tyre eventually makes it through the chainstay.

 

[Ajax Bay]

How many spokes were unbroken? On your 'old commuter'.

 

[Yellow Saddle]

The size of the wobble after a broken spoke is a function of spoke count. The fewer the spokes, the larger the wobble. Anything under 28 spokes and you will almost certainly not be able to ride further.

 

[Dogtrousers]

I'm not a regular spoke breaker but I had one go in a 28 (or maybe even 32 I forget) spoke rear wheel while grinding up a hill. It let go with a bang and really distorted the wheel badly. I had to open the QR on the (rim) brake and it was wobbling and rubbing like nobody's business. Fortunately I was only a few, mainly downhill, miles from a station. I had it replaced but another spoke went soon after, so I retired the wheel. I'm no expert but the tension on the spokes in that wheel seemed very high. (As noted, I'm inexpert and that may be hogwash). Either way, I didn't return to the original wheel builder.

 

[lostinthought]

I'm not a regular spoke breaker but I had one go in a 28 (or maybe even 32 I forget) spoke rear wheel while grinding up a hill. It let go with a bang and really distorted the wheel badly. I had to open the QR on the (rim) brake and it was wobbling and rubbing like nobody's business. Fortunately I was only a few, mainly downhill, miles from a station. I had it replaced but another spoke went soon after, so I retired the wheel. I'm no expert but the tension on the spokes in that wheel seemed very high. (As noted, I'm inexpert and that may be hogwash). Either way, I didn't return to the original wheel builder.

The ideal spoke tension is, practically speaking, as high as possible (it is limited by rim strength), so that won't have been the problem. Spoke failures do tend to follow each other, however: the reason is invariably that a number of them are already cracked mostly through by slow-developing fatigue fractures, which are practically impossible to see before total failure. There may be a handful of adjacent spokes all hanging on by a thread, so to speak, and they finally give up in turn, as the wheel is weakened by each successive failure.

The blame for this is generally ascribed to a procedural error when the wheel was first built- inadequate stress-relieving, and failure to correct the spoke line. Failures do happen however even to well built wheels occasionally.