Q. A spoke in my back wheel has broken, but it’s not sticking out or catching on anything.
Do I need to replace it , after all there’s loads of others in the wheel
A . The short answer is ‘Yes’, and pretty soon, too.
Obviously the spokes hold the wheel hub in the centre of the wheel rim, but also the spokes are set up in triangles from the rim down to the hub, but also from the rim down to opposite sides of the hub to make another triangle.
A triangle is a very rigid formation. Just think, a three legged table doesn’t rock, but if one leg is broken it all falls down. On a cycle wheel all the spokes working together keep the rim the same distance from the middle all the way round, but also keep it central between the wheel forks and the brakes.
It is likely that with a broken spoke one of the brake blocks will be rubbing and I have seen some people slacken the brake off so it doesn’t rub, but then it won’t work properly, will it?
That is because instead of being straight and flat the wheel starts to be bent like a Pringle, with two opposite edges bent to one side and the other bent to the other.
The longer you ride like that the worse the Pringle shape will be, and eventually the wheel will be beyond repair and you’ll need a new wheel.
Particularly with the back wheel every time you push down on the pedals the chain turns the gear at the middle of the wheel and the spokes transmit the twist to the rim at the outside of the wheel. That means that the spoke at the middle is turned a tiny amount inside the fixing hole and over time that can wear the joint and I expect that’s where your spoke has broken.
So it’s wise to inspect it and check the other spokes very soon.
Indeed, if you find that another spoke breaks soon then it means that they are all worn and will break one after another so it will be better, after the second broken spoke, to have them all replaced.
You can do this yourself but it can be complicated, and need special tools. Bike shops can do this for you, and Halfords for example will replace up to five spokes for £20.00 which is a lot less than the cost of a new wheel.
Incidentally, did you realise that your bike is hanging from the top of the wheel rim by the top three or four spokes, and the rest of them just keep the wheel round?
On a wooden cart wheel the weight pushes down though the bottom spokes, and any tugging on the top spokes would just pull them out of the rim. On a bike any downward pressure on the lower spokes would just bend them. They are only thin bits of wire, really, and all their strength is in tension. Typical cyclists - everything is not what you expect.