Radial lacing refers to a lacing pattern where the spokes go straight from the hub to the rim without crossing. Recently, this has become popular with custom and machine-built wheels because of the "look" and the supposed weight savings. Shorter spokes = less weight. Weight is important, but there are some problems inherent to radial lacing.
Rear wheel spokes have to transfer drive torque from the hub to the rim. To do this efficiently, some of the spokes need to be angled nearly tangent to the hub. If all of the rear-wheel spokes go straight out to the rim radially, they allow the hub to twist quite far before they catch up and drive the bike. Disc brakes use the spokes to transfer torque as well, so they also need to have at least some spokes angled out to the rim. Some believe that non-drive, non-disc wheels don't need to transfer torque so they can be radial, and some of the spokes on a drive or disc wheel can of course be radial, in theory. However, Gravy contends that all wheels under braking transfer load via spokes.
Radial lacing allows shorter, lighter, stiffer (because they are shorter) spokes, making for a lighter and stiffer wheel, but those stiffer spokes are more likely to break. They also impose higher stresses on the hub flange because radial lacing puts the greatest load on the place where there is the least material. Shimano has banned radial lacing on its hubs and several hub manufacturers have developed radial-specific hubs to answer the current demand.
All sorts of mixtures of radial and cross lacing options are possible, but they save only a little weight over good-ole cross lacing, and make life quite a bit harder on the hub and spokes.
Although low spoke-count, radially laced wheels are light and look cool, we've found that a bike handles much better with traditional three-cross, 32 spoke wheels. In the front especially, radially laced wheels seem to wander and don't hold their line as well. Put on a well-built three cross wheel and suddenly the front end responds faster and is more precise.
Gravy builds wheels to optimize strength and reduce stress on the wheel. Radial lacing puts the spoke doing the most work directly in the load path, which increases the stress/load on both the spoke and the hub. Building with crossings (tangent) puts the spoke doing the most work well past and ahead of the load path, saving all parts of the wheels from undue fatigue. An additional benefit to building two or three, or even four cross wheels, compared to radial, is the protection from chain suck. For example, if you throw your chain into the spokes, our "outside pulling" pattern will help your chain not to get sucked into your wheel.
A Note on Crossing Pattern Selection
In Gravy's experience, two cross spokes will be on average 10mm shorter and might save you 30 grams for the entire wheelset when compared to three cross. However a two cross pattern on a 32-hole rim has decreased trianglization compared to a three-cross pattern. The trianglization occurs where the spokes meets the hub flange. The smaller the triangle, the less stability at the hub. Spoke count also contributes to the trianglization. More spokes means less trianglization, while less spokes means more trianglization. Optimum tranglization occurs at the 9:00 o'clock and 3 o'clock spoke position, the widest base triangle. A 36-hole 4 cross, 32-hole 3 cross and 28-hole 2 cross all roughly have the same trianglization. If you want to save some weight and it makes sense for your build and style of riding, a 28 hole, 2 cross wheel makes much more sense than a 32 hole radial one.