If you ride a wheel with a spoke missing and don’t straighten it, you will bend the rim permanently. Yet, as only long-distance riders heading for the Himalayas ever seem to carry spare spokes, there’s a limit to what you can do if one does break. Rear wheel spokes can’t be replaced unless you have the tools to remove and refit the cassette, making an emergency fix unlikely. But you can adjust the surrounding spokes to make the wheel as straight as possible, getting your brakes to work better (if you have rim brakes), and making it more likely you will be able to fix the wheel properly later.
First, render the snapped spoke safe by preventing it from wrapping around anything else. If it’s broken near the rim, wind it around an adjacent spoke to keep it from rattling around. If it’s broken near the hub, bend it in the middle so that you can hold it still. Use a spoke key to unwind the nipple so that the spoke drops out of the end of the nipple. If it’s broken in the middle, which is the least likely, do both.
Lift up the wheel and spin it gently to see how bent it is. There will usually be a single large bulge where the spoke is broken. Use a spoke key to loosen the spokes on either side of the missing one. It can be confusing working out which way to turn. Look at the spoke you want to turn and imagine you can see the top of the spoke nipple through the tyre. To loosen a spoke, turn it so that the top of the spoke head turns anticlockwise.
With rim brakes, check the clearance between brake blocks and tyre. You may find that the tyre rubs on the brake block in the broken spoke zone. If this is the case, loosen the Allen key bolt that holds the brake block in place, and move the block down slightly so that it clears the tyre.
Straightening a bent wheel
With a spoke key, you can sometimes get the wheel straight enough to ride safely. As a guideline, if the wheel has more than 2cm (1 inch) of sideways movement when you spin it, you are unlikely to be able to straighten it with a spoke key. One seldom appreciated advantage of disc brakes is that the brakes continue to work properly when the wheel is bent.
Turn the bike upside down. If it’s the back wheel, get behind the bike; if it’s the front, get in front so that you’re in line with the wheel. Spin the wheel and look at the area where it passes between the brake blocks (or, if you have disc brakes, where brake blocks would be). If the wheel is too wobbly to pass between the brake blocks, release your brake units. If it’s too wobbly to pass between the frame, pick your bike up and start walking home.
If you think you can straighten the wheel, spin it a couple more times and look at its shape. You need to identify the point where the wheel is most bent – the biggest bulge away from the centre line. If you have rim brakes, use one of the brake blocks as a guide. Hold the brake unit still and spin the wheel, watching how the gap between the brake block and the rim changes. If the wheel is badly buckled, you’re going to have to make a rough judgment about where the centre of the wheel is, and work towards that. You won’t get perfection in the field – just get it round enough to roll.
Adjustments of a quarter- or half-turn of the nipple are plenty. It’s easy to start with a buckled but salvageable wheel and end up with a useless pretzel by going too fast. Much better to stick to small steps. Check the previous page if you’re not sure which way to turn the nipple.
“If you ride a wheel with a spoke missing and don’t straighten it, you will bend the rim permanently”
Step 1 : If you don’t have rim brakes, you will have to improvise a gauge to measure the wobble of the wheel against. Zipties are invaluable here either ziptie a stick to the chainstay or fork so that it sits level with the rim, or zip a tie around the fork or stay, leaving a long tag hanging off. Use the tag as your gauge.
Step 2 : Spin the wheel again and stop it when the middle of the biggest bulge is level with your gauge. Look at the spokes on the wheel. You’ll see that alternate spokes lead to opposite sides of the wheel.
Step 3 : Choose the spoke at the centre of the bulge. If it leads to the same side of the wheel as the bulge, loosen this spoke and tighten the spokes on either side. A quarter- or half-turn should be enough. If the central spoke leads to the opposite side of the hub, tighten this spoke and loosen the spokes on either side by a quarter- or half-turn. Spin the wheel again, and pick out the biggest bulge.