What’s the reason for high spoke tension?
It’s not what you think.

by John Neugent

Tech articles | Commentary articles

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

John Neugent

Les Woodland's book Paris-Roubaix: The Inside Story - All the bumps of cycling's cobbled classic is available as an audiobook here. For the print and Kindle eBook versions, just click on the Amazon link on the right.

John Neugent writes:

For the Paris-Roubaix race, many mechanics loosen the spokes to give a smoother ride. The problem is that lower spoke tension has no effect on wheel stiffness. Steel has the same stiffness under any tension, as long as there is some tension.

Why then, is high spoke tension important? Back in the old days no one used spoke tensiometers to measure spoke tension. Most wheels, even custom wheels, used 32 or 36 spokes and with that many spokes, tension was not an issue.

Bernard Hinault time-trialing back in 1981, using normal rims with probably 32 spokes. Sirotti photo

Mavic introduced wheel systems in the mid '80s. The advantage of a system is it allows one to design wheels with as many spokes as you want. So Mavic started using much lower spoke counts, which does two things. It lowers weight and decreases drag. These both have a major influence on performance. It also puts a lot more stress on rims, spokes, nipples, and hub shells. It took rim, hub, spoke, and nipples makers decades to adapt, and if forced wheel builders to do the same.

Lower spoke counts meant much more stress and wear on the components. So, let’s say, a 24-spoke rear wheel would loosen sooner than a 36-spoke wheel under the same initial tension. The goal then, was to make the tension as high as possible, and to do that builders needed a definite calibration so that the spokes were as tight as they could reasonably be. But it’s not that simple either.

Front wheels (on caliper brake bikes) almost always have fewer spokes than the rear of the same set because there is much less stress on them. The rear wheels take about 60% of the weight of the rider and are also the drive wheel. Both of these issues dramatically increase the stress on the rear wheel and, because it is dished (to make room for the sprockets), make the drive side spokes under much more load.

So when we look at spoke tension we are primarily looking at drive-side spoke tension since that’s going to be the highest. Ever since bikes started using multiple gears there has been a tendency toward more gears. What started out as 1, soon became 3, and when I started riding it was 5. Now it is 12 and I pray to the Lord every morning hoping it doesn’t go to 13. The effect of this is that the gears continue to take more space and move the hub flange toward the center of the wheel. When this happens, two things result. The drive side spokes get tighter and the non-drive side spokes get looser. Now, when you add a smaller number of spokes to the equation, you challenge the system even more.

Currently, drive-side spokes have to be under relatively high tension just so the non-drive-side spokes are under any tension. This is the Achilles Heel of the system because if a non-drive spoke gets loose, it allows movement.

Julian Alaphilippe at the 2021 Tour de France with a modern low spoke count set of wheels. Sirotti photo

Remember what I said in the first paragraph. A spoke under any tension is as stiff as a spoke under a lot of tension. That’s all true until it’s under no tension. When it’s loose, the resultant movement creates wear. So the higher the initial drive side tension, the longer the wheel is going to last.

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.