My son texted me from university 400 miles away to tell me his spokes were rattling. I feel a wee bit responsible, since I built this wheel for him on a Brompton 8-speed conversion.
So how do you teach spoke-tensioning by email? I had a go, and thought I would share my attempt here.
I don’t know if this is how the pros go about it – it’s just what I would do. If your wheel has gone a bit wonky, you may be safest taking it in to a bike shop to get looked at. But if you’re happy to tinker, read on.
This is what I wrote:
For tightening spokes, once you have your spoke key (suggesting 14G), invert the bike and:
- Ping all the spokes and work out which has the highest pitch. Make a note of that pitch as a benchmark. You may need to note a different pitch for each side of the wheel, if the spokes are different lengths on each side. (e.g. crossed only on one side.)
- Work your way round the wheel starting from the valve (useful marker) and tighten every loose spoke until the spoke key is giving a little bit of resistance, but you are not putting much effort in to turn. (This should draw the tension together across the wheel and avoid over-tightening one side or another)
- Work round the wheel a second time, adding a quarter turn to every spoke. Only make an exception if you come across a nipple that is really tangibly looser than its neighbours – if so tighten it more to allow it to ‘catch up’ with the others.
- Check the pitch of the spokes – if many are well below your benchmark, keep working round the wheel – only a quarter turn at a time.
- Don’t tighten any above the benchmark pitch yet.
- When most of the spokes are up to pitch, single out those that are noticeably below. Give these an extra tighten. This is not an exact science – they don’t all have to be exactly in tune.
- Read point 15.
- Check the wheel for trueness. Viewing the wheel from above, push a brake block in to the rim until it is nearly touching. Spin the wheel. See if the width of the gap between rim and block oscillates. If it does, find a point where the rim comes in closest (usually it rubs on the block.)
- Looking at the spokes laced on the side of the wheel furthest from the block, (lets call them Takers), identify the spoke nearest to the middle of the section of rim that rubs. Then note the two Takers either side of this middle spoke – so you are now looking at five Takers in all. Then notice that between the five Takers, there are four spokes on the side of the wheel nearest the block – let’s call them Givers.
- Now loosen the nipples on the four Givers by half a turn, and then tighten the nipples on the five Takers by half a turn. If you want to be really flash, only give the spokes at the ends of your rows a quarter turn.
- Spin the wheel again. If the rubbing has stopped at this point, the wheel is truer. If it still rubs, repeat the process.
- Once you have established a small gap where there had once been a rub point (say 1mm), you can use this technique to tackle another oscillation of the gap between rim and block. Find the mid-point of the rim’s ‘wobble’, and repeat. Of course, you can pull the rim in towards the block as well as pulling it away by reversing the sides you tension/loosen.
- Once the rim is true, you may wish to go round a couple more times and add a quarter turn throughout, since clearly the rim was not tensioned high enough before.
- Then check trueness again and correct as before.
- You may also want to check whether the wheel is still round. Look at the brake-block side-on, spin the wheel, and see whether the path of the rim stays still beneath the block – ie. Often there is some wobble, which the tyre under pressure sorts out. If it is drastic, however, you can correct this by loosening a sheaf spokes on one side of the wheel (viewed from the side) and tightening a sheaf on the other, in order to centre the hub like a ‘bullseye’. But this is best done before the truing described above. Use a ruler to measure the distances from the hub to the rim. 1 or 2mm error is acceptable.
- The other element here is dishing. The spoke length should sort this out. The spokes on either side of the hub need not be at the same angle to the rim (i.e. viewing a horizontal spoke from above) – one hub flange will be nearer the center line of the rim than the other. All the matters is that the tyre, viewed from above on the upturned bike, lines up with the seatpost part of the frame, which itself (you will notice) is offset within the steel wedge-shaped part of the frame which holds the bottom bracket. In other words, Brompton rear wheels are not designed to sit centrally within the rear triangle! (Notice the deliberate dent in the frame on one side where otherwise the tyre would rub against it.)
- If the tyre (viewed from above, and looking down the length of the upturned bike) does not line up with the seat-post, you can correct the dishing by loosening all spokes on one side of the hub by a half turn, and tightening all those on the other side by a half turn. Check, and repeat if necessary.
- Relax, and eat a large pie.
- Remember this is an iterative process – so feel your way and use your intuition. Fiddling with spoke tension in one place will change what you have done elsewhere, so don’t try and get any one area too perfect before moving on. Also remember a quarter-turn all round is a gain in tension of double that across the wheel – hence the small increments.
- If still hungry: donuts.