Ask a Mechanic: Understanding Spoke Design and Application

Doug says, “Can you give me an overview of spoke design and spoke application?”

When choosing spokes for a wheel build, there are three things to consider: gauge, how they are butted, and shape. Once you understand these three factors, you’ll be better prepared to either build or purchase your next wheelset.

Let’s start with gauge, which is just another word for thickness. Original nomenclature rated gauge in gradations from 16 to 13, with smaller numbers corresponding to thicker gauges.  Most modern sources refer to spokes by their diameter in millimeters, ranging from 2.3 to 1.6. 2.0 and 1.8 millimeter spokes are the most commonly used for road and mountain applications. Typically, 2.3 mm spokes are reserved for heavy-duty use, like touring or tandem riding, and 1.6 mm spokes are reserved for road race applications.

Next, you must decide on butted or straight gauge spokes. “Butt” refers to a change in diameter, so a double-butted spoke is thicker at the ends and thinner through the rest of the spoke. A single butted spoke is thicker at the hub end and thinner throughout the rest of the spoke. Double butted spokes have an advantage over straight gauge and single butted spokes because they are as strong as an unbutted spoke, yet lighter and more comfortable to ride. With their thinner center section, double butted spokes are more elastic and tend to stretch rather than break under stress as a straight gauge would.

Single butted spokes provide more stiffness than double butted spokes, without being as brittle as straight gauge spokes. For this reason, some downhill wheels use single butted spokes. However, if you want an ultra-stiff wheel, then straight gauge might be for you.

Triple butted spokes are both rare and expensive. Depending on how thin the center section is, they may not be strong enough for your intended use. As spoke material and quality has improved, triple butted spokes are rarely necessary or worth the expense.

Bladed, or aero, spokes are round at the ends and flat or elliptical in the middle section. These spokes offer both weight and aerodynamic advantage at higher speeds. Thanks to the flat section, bladed spokes also hold higher tension and distribute tension more uniformly throughout the wheel build.

Finally, there are two different styles of spoke head: straight pull and J bend. I’ve already given my take on the subject in another Ask A Mechanic video, so if you’re interested in hearing more about spoke heads, click here (point to upper right).

Thanks for watching and good luck.