Disc Wheel Lacing

I'm building up a new wheel set, my first using disc brakes. These brakes affect the lacing design because the torque applied by the brakes is carried by the spokes to the rim and tire. In contrast, rim brakes (as on most road bikes) apply no torque at all to the spokes.

While I want the wheel set to be strong and reliable, I also want to optimize its weight against the strength required for each part of the wheel. The spokes are a significant part of the weight, and they are available in different thicknesses. I made up a lacing pattern which uses two different spoke thicknesses in different parts of the wheel.

The front wheel has the most complex pattern. The only torque these spokes carry is during braking, so it's all in one direction. I'm using the thinnest spokes in the positions that do not increase in tension when the brake is applied. The thin spokes are also laced inside the hub flanges. The thicker spokes, which carry the brake tension, are laced outside the flanges. This provides a few benefits:

• When braking, these high-tension spokes are outside the flanges, forming the widest possible bracing angles and therefore the stiffest wheel in terms of resisting side loads.
• The thicker spokes are the ones furthest from the center plane, so the tip of a stick is more likely to hit a thick, strong spoke instead of a weaker, thin one.
• The simple rule of thin spokes on the inside of the flange makes them easy to track. The thin spokes must be tensioned more carefully because they can twist or "wind up" more than the thicker ones, and they must be kept untwisted. (I've also marked the thin ones with a pen during the wheel build.)
  

The rear wheel uses thin spokes only in the same, non-brake-tension position, only on the brake side of the wheel. The drive side (with the cassette gears) has thicker spokes in both directions, to handle both pedalling and brake torques. (I'm treating these hubs as capable of carrying significant torque through the hub shell to the opposite flange, but I consider that torque important only for braking. My pedalling forces can be carried on just the drive side of the rear wheel.)

The main downside to optimizing the lacing this way is complexity. It's easy to put the wrong spoke in a given position. And more spokes need to be purchased and tracked - for example, there are four different spoke sets in the front wheel. (Two thicknesses x a different length for each side.) The rear wheel has three different spoke sets.

I'm rusty enough at wheel building that I made a few mistakes at the beginning, but now both wheels are laced and I've started tensioning the rear. I'm happy with the result so far, and am excited to ride them!

[Notes: The spokes are DT Competition (2.0/1.8mm) and DT Revolution (2.0/1.5mm). All lacings are three-cross (3X). All spoke nips are brass for strength and resistance to corrosion. Hubs are Shimano XTR which are available near half price these days as they seem to be out of favor, and I've had good experiences with my Shimano hubs over many years. I think they're a good value now. Also, I like the loose ball design for hubs because I know how to rebuild and preload them - I'm not excited by the trend toward cartridge bearings. On the other hand, they have the lowest flanges I've seen on a disc hub, so they demand high spoke tension and are probably best for XC-only riding. The rims are Stan's Olympic ZTR, a lightweight and slightly radical offering from a new small manufacturer. I plan to run these wheels tubeless, at least at first, and these rims are designed to work that way or with tubes. Thanks to GC for his great info and experience on these rims.]