I have been finding out first hand that wheel building is a time consuming activity, but not without its own satisfaction. Because I was building up completely different wheels from the originals I needed to measure the hubs and rims, and decide on the appropriate cross pattern in order to work out the new spoke lengths.
The online spoke calculator that I used has given me the wrong lengths, but I’m not sure why. I had also ordered those said wrong lengths which I only found out after completing a wheel.
I am going to have to find a reliable calculator, or at least one I can better understand.
Of course if you are rebuilding exactly the same wheel with new components then you only need to get the same length spokes again or re-use the old ones if they are in good condition … don’t forget to weigh up the cost of a similar pre-built new wheel, to see if it’s worth your time to do all this !
The first wheel was the front one, and the ordered spokes were too long for 3-cross. I decided to use a full set of shorter spokes that I already had, which at 287mm were around the right length for radial spoking. Radially spoked wheels ( i.e. zero cross ) are pretty, but only suitable for front wheels because they lack torsional strength and are more stressful on the hub flanges. Hopefully this one can cope with rim braking but as the coaster rear will be the main brake I think they will be all right (touch wood) with some careful initial testing.
Spoke crossing refers to the number of other spokes each spoke will cross between the hub and rim, with 3-cross wheels being the traditional norm. The last or outer cross is the opposite of the previous crosses e.g.. over-over-under or under-under-over for 3-cross. This is referred to as interlacing and helps give wheel strength.
The radial spokes turned out to be slightly long, so I had to file the ends down a couple of millimetres flush with the nipple ends so as not to puncture the rim tape and tube later on. The wheel was built with a little more tension than normal, as recommended by some sources for radial spoking, and I fitted eyelet washers under the nipple heads as an extra precaution against them pulling through the rim.
The rear wheel turned out to be loose, because the spokes were too long to fully tension for 3-cross. Frustrated, I re-tried for 4-cross and they worked a treat. 4-cross is supposedly the strongest pattern, though there is possibly no real advantage on this particular wheel over 3-cross, apart from using up the extra spoke length.
Also with 4-cross a spoke can interfere with the head of its adjacent partner unless the hub is small diameter, making them potentially harder to remove if broken.
I could have easily messed it up here, but if the lengths are only slightly wrong there is still a chance to line up a loose spoke against the built wheel and get a pretty good idea by eye whether the wheel will work with a different crossing.
I used the Lennard Zinn book – “Zinn and the Art of Road Bike Maintenance” – to learn the basics of lacing, it is a fairly repetitive process once you have worked out the position of the initial spoke in each set.
Therapeutic even, as long as you remain calm, focussed, and are not time constrained … otherwise put the wheel down and finish it at some other point !
The tools I used were a Park Tool SW-7 spoke tool, a screwdriver for the nipple ends and a Park Tool TM1 Spoke Tension Meter. The latter is easy to use, comes with charts and instructions, and takes a lot of the guesswork out of tensioning, though they do suggest contacting the component manufacturers for their correct tension specs. Having a wheel fail while riding is not something to take lightly …
For reasonably accurate final truing I think that a wheel truing jig is almost essential.
According to Park Tool, the spoke tensions on each side of the wheel should be within plus or minus 20 percent of the average tension of all those spokes for the wheel to remain stable under normal use. This is not easy to guess by hands alone unless you already have a lot of experience, which of course I don’t.
Even if the spoke tensions are all exactly equal the wheel still might not be true, so fine tuning is generally always required.
Doing one adjustment affects everything else because the wheel components are all interconnected under tension – that’s why wheel building is considered another of the bicycle black arts, and why it pays to go step-by-step and slowly !
It would probably be easier to begin with new (hopefully straight) components for your first build, but with good used parts I suppose there is more freedom to experiment. Do plenty of research on the subject beforehand, of course.
Happy Cycling !