A Little Washer Can Make a Big Difference
by John Neugent
John Neugent probably knows more about bicycle wheels than anyone else alive. Maybe more about bikes as well. He's spent his life in the bike business, at every level. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price. If you are in the market for a set of wheels, please, check out John's site. He really knows his stuff. —Chairman Bill
It wasn’t that long ago that all wheels came with lots of spokes—normally 32 to 36. Then in the 80s, Mavic introduced wheel systems with remarkably few spokes. All of a sudden people realized that spokes slowed them down. Think of a wheel as a giant egg beater. The more spokes, the more air you are going to churn and the slower you will go.
When I first started selling lower spoke count wheels, people would routinely tell me they were going 1–2 mph faster. Lower spokes mean less weight and better aerodynamics.
But like anything else, it comes with a price—more broken spokes and cracked spoke holes.
Spoke makers have taken giant steps to reduce spoke failures. They still happen but they are much less common. In "the old days" spokes virtually always broke at the bend. Now, that is almost unheard of (makes you wonder why wheel companies would use thread in spokes but that’s another story). Now spoke failures typically happen where they are butted.
But the biggest price for low spoke count wheels are rim cracks: in particular, the drive side spoke holes of the rear wheel. In fact, that’s typically where low spoke wheels wear out first. But there is a simple solution that will go a long way to increasing durability: spoke nipple washers. Also, since there are no patents on washers, it’s a solution anyone can use.
The addition of a washer on the drive side rear wheel (the only place it is needed) does many things. The most obvious is that it adds material where it is needed most. Most alloy rims have a spoke bed that is 2mm thick. The washer adds another ½ mm—or 25% more material.
The biggest advantages are not obvious. When you tension a rear wheel, the drive side spokes are under very high tension. Many high end wheels go up to 130 kgf—and some up to 150 kgf. The nipple has a round shoulder and the spoke hole is a plain drilled hole with a square edge. As you turn the nipple at high tension it stresses the spoke hole. By adding a washer that stress is primarily directed at the washer so the rim hole maintains much of its integrity. I also grease the washers on both sides so the nipple turns much easier and puts less stress on the washer, nipple and spoke hole.
Modern wheels have more and more dish as the room for more and more gears is needed. As you dish the wheel more, the non-drive-side spokes become looser—to a point where they can easily loosen if their initial tension isn’t high enough (even when using Loctite it can be an issue). The only way to increase the tension on the non drive side spokes is by increasing the tension on the drive side spokes. By adding the washer you can increase the drive side spoke tension without endangering the integrity of the rim.
You can buy rims with eyelets on all of the holes but they add unnecessary weight, and spoke holes rarely fail anywhere except on the drive side rear. The next time you build a wheel or have one built, get internal washers on the drive side of the rear wheel. You will get far greater durability at a very modest increase in cost.
In figure 1, you see a rendering of a spoke hole in a rim and a plain Sapim Polyax nipple. It’s easy to see that the shoulder of the nipple will dig into the sharp edge of drilled rim hole. Not only that, it will dig into it under high pressure with rotational torque.
Figure 2 shows a rendering of the washer. It mates perfecting with the shape of the Polyax nipple.
Figure 3 shows the spoke nipple with washer in a spoke hole. Since the washer is greased on both sides, the nipple will turn more freely and also seat with less deformation of the spoke hole.
Figure 4 is a photo of the Sapim HM Washers I use. These are readily available to anyone.
John Neugent was was one of the first to establish quality hand building in Taiwan around the turn of the century. He now owns Neugent Cycling, a firm devoted to delivering world-class equipment at the lowest possible price.