Getting myself back on the road for another ironman journey has been extremely satisfying, partly as it gives me the excuse not just to ride my bike a lot more, but also to work on it and talk about it. Recently I have had to do a bit of work on my wheels, which take quite a pounding on the dirty potholed roads of Tanzania. A bike wheel is truly an amazing piece of engineering and physics, and the more I have got to know about wheels by building and working on them , the more beautiful I find them. For example: If you sit on a wheel rim, without spokes in it, you’ll break it- that’s how weak and flexible they are. Likewise any adult would be strong enough to fold a spoke in half if they wanted. And the more you pay for spokes and rims (often) the weaker they are on their own. But when built properly into a wheel, the constant, even, and sometimes enormous tension which is being applied in 24-ish places around the hoop prevents it from buckling or breaking, even under incredible load. It will stay straight and true, holding a rubber tube which is pulling sideways and outwards at 120psi or sometimes more, even when a 75kg man rattles down a bumpy hill on it at speeds approaching 100kph. Achieving this breathtaking durability, while keeping your wheel round enough to use, is supposedly the hardest thing in bike mechanics. But I disagree, it seems to me that it just takes a bit of patience and practise.
This is not the official way to learn, but it worked for me.
Find a really old wheel. Try tightening and loosening a spoke or two and see how it affects the shape. You’ll need to fit the wheel in a wheel jig or just spin it between the brake blocks of a fork in order to see the wobble in it. Try to adjust a few spokes to make it straighter.
Take a spoke out, have a coffee, and then refit it. You will need to thread it correctly between the other remaining spokes (memorise how it went or just copy another one). The re-tighten it to make the wheel straight again.
Once you can reliably straighten this wheel, even after removing and replacing 2 or 3 spokes, you could try to build a new one. I recommend starting with the fairly cheap bits to start with, say about 10 quid for the hub and the same for the rim.
Spoke length can be calculated if you’re a really good mathematician, if not you can use free online calculators, e.g. the one written by DTSwiss. If the result is between sizes, get the size below your results, i.e. shorter. Your biggest challenge, I find, is in buying spokes of the right length, which can take ages to order.
Once you have your bits, copy the spoke pattern of another wheel, in other words make your spokes cross each other in the same way as an example that you can look at. It will help if your eg wheel has about the same number of spokes as the one you’re building. Pay attention to which way the spokes go into/out of the hub, and then overlap each other. Tighten spokes a tiny bit at a time. Unless you are building radial wheels (and if you don’t know what that means, you’re probably not!) be sure to put some grease between spoke and nipple. Don’t build radial rear wheels – although you can build radial just on the non-drive side which looks cool. Don’t build radial wheels if you have disk brakes. But don’t imagine I am against radial wheels, they are definitely good on the front of road bikes.
As the spokes become tight, pay more and more attention to how straight and true the wheel is. (What’s the difference? A wheel can be wrong in two dimensions, side to side or up and down). Do not rush the final adjustments, take time and remember this is an art not a science. I find it works best with a bottle of Fuller’s ESB and a good CD. You are trying to get within a mm of play in any direction but you will not achieve perfection. If you believe you have got a perfectly straight and perfectly true wheel, then you need glasses.
Finally, after a ride or two, go through the fine-tuning again. The bump and grind of a few tens of km will shake a few things loose and expose any weaknesses. Address this and re-straighten now to avoid breaking a spoke or long term deformation of the rim.
