About our wheels: spokes and spoke nipples
Spokes and spoke nipples are just as important as the hub and rim so we take a lot of care in choosing and correctly using them in our wheels.
These are the tiny nuts which thread onto the spokes and attach them to the rim. They are small and light but have to withstand a force of 1200N (equivalent to 120kg). If a spoke nipple breaks then the wheel will go out of true in the same way as when a spoke breaks, so choosing reliable spoke nipples is an important part of building good wheels.
We always use Sapim spoke nipples since these have proven themselves to be extremely durable over the years - better than any others we've tried. Problems we have seen with other spoke nipples are corrosion (especially from salt water), damage when building the wheel due to being too soft, and bad alignment in the rim. Sapim spoke nipples are extremely corrosion-resistant, they are very strong so don't suffer any damage when building the wheel, and they are shaped so that they align well with the spoke - the head can rotate a little inside the rim preventing breakages.
Spokes have a hard life in a wheel, especially in a rear wheel. They are wound up to a tension equivalent to 120kg, and every time the wheel goes round the tension drops at the point where the spoke is at the bottom, then it's back up to 120kg. This happens 1 million times for every 2000km ridden, so failure through fatigue is a big problem for spokes. We only use Sapim spokes in our wheels due to their proven reliability, and we experience almost zero failures.
We are often asked about bladed spokes. Sapim CX-Ray are a type of spoke used in many high-end road wheels but they are much more expensive than round spokes. They are forged in a way that leaves the middle section between the head and thread as a flat profile, 0.9mm deep and 2.3mm across. In theory this thin cross-section gives them an aerodynamic advantage, and Sapim also claim "extremely high fatigue test results" because of the forging process. But, aero test results show there is very little difference between CX-Rays and their round equivalent, the Laser - it has been measured at 1 watt at 30mph - and also the round Sapim spokes almost never break anyway. So most of our standard wheel build specs come with round profile spokes. CX-Ray "upgrades" are available at between £70 and £100 per pair of wheels for riders after every last bit of energy saving. Our carbon road wheels use CX-Ray spokes as standard.
It's all very well having the best spokes and nipples (which Sapim are), but if you don't prepare them properly there will still be problems. When an unprepared spoke is at high tension it becomes difficult to turn since it "binds" with the nipple - you turn the spoke nipple but the spoke twists rather than threading onto the spoke, which causes damaged spoke nipples, twisted spokes, and is just generally hard to build a perfect wheel since small adjustments are impossible. So all of our spokes are degreased in an ultrasonic bath before being individually prepared with Wheelsmith Spoke Prep, a coating which is painted onto the threads. This completely eliminates binding as well as protecting against corrosion by placing a barrier between the spoke and nipple, and also makes the wheel much easier to true in future. It's a slow process applying and drying the spoke prep, but makes a dramatic difference to the wheel performance and building process - one of the reasons we won't work on anyone elses wheels.