Damaged wheel

[Yellow Saddle]

The load taken by the wheel is normally spread evenly around the whole rim, this sort of damage causes a weak spot (where the stress in concentrated) and, once damage like this has occurred, it's more likely to spread.

Oddly, the more expensive the wheel, the more susceptible it's likely to be. A cheap steel wheel has loads of redundancy but lighter designs have thinner walls and so are less able to tollerate damage.

Not saying this wheel will definitely fail, just that it's not something I'd take the risk on

No, it doesn't work like that. The load is not taken evenly. The load is only taken at the bottom, in the load affected zone. This zone is analogous to the tyre's contact patch but bigger. It usually, depending on the number of spokes, span about three spokes. In this zone the spoke tension DECREASES when the wheel is loaded. The rest of the spokes keep their tension and nothing happens in the rest of the wheel.

Stress risers don't come into play here.

Price has nothing to do with it. Key factors are number of spokes, rim profile, type of metal alloy and to a lesser extent, the thickness of the rim walls. There is no redundancy here, that's a different concept.

The wheel has failed. However, failure of this type is not catastrophic and can safely be ridden up to the point where the rim rubs on the brake pads, where it becomes inconvenient to ride. It isn't dangerous and as @Illaveago pointed out in the post above, the OP has probably been riding it like that for many kilometers before discovering the crack.

 

[Gary E]

Ah, I see your angle now. Probably shouldn't have fallen into your trap. You're right, what would I know?

Bye

 

[Yellow Saddle]

Ah, I see your angle now. Probably shouldn't have fallen into your trap. You're right, what would I know?

Bye

Sarcasm or self-pity? Stop it. I had to understand what you meant first, before responding. It is about the understanding of a bicycle wheel, something that is mysterious to most people and it therefore attracts a load of myth and misconceptions.

 

[Roadhump]

As you say he has been riding it as normal until he discovered the fault, so it is the fact that he now knows of the problem that makes him more wary.

That is true.

This must have happened quite recently as I try to make sure I clean and lube my bikes after every 150 miles or so. The wheels on this bike tend to show dirt more, especially the rear one which is the one now damaged, and I always wipe them with a cloth with a touch of GT85 to et rid of grease and dirt. I hadn't noticed it last time I cleaned the bike a couple of weeks ago.

I guess I have been riding on the wheel since the crack appeared, and perhaps as @Yellow Saddle says, it is safe, but as you say, now I know it is there, I am wary of it, and I don't have confidence in the bike. One of the things I use this bike for is when I do Bikeability training with schoolchildren, which is why I wanted to use it tomorrow, but I feel I can't trust it to be wholly reliable if I have to supervise a few 10/11 year olds riding on public roads. Not a massive problem as I have another bike available, but I would rather stick to this one if I could.

 

[vickster]

Can't you get a new wheel from your LBS?

 

[Roadhump]

Can't you get a new wheel from your LBS?

I probably can, I am off to find out when I have finished my cup of tea. Depends which is cheaper, getting it repaired or a new wheel, plus which can be done sooner.

 

[Illaveago]

Good luck with your wheel hunt.
It was interesting to see just how thin the material was where the spoke goes through the rim.

 

[Yellow Saddle]

Good luck with your wheel hunt.
It was interesting to see just how thin the material was where the spoke goes through the rim.

These are some images from my personal photo collection of wheels I've dealt with over the years. All the walls are thin, even the carbon ones.