What you need to know after you think you know everything there is to know about wheelbuilding
by John Petricciani
Wheel types are as numerous as the myriad of bikes they’re spec’d on. Despite the countless geometries and style-specific hardware, from downhill to gravel to road and everything in between, some things about wheelbuilding remain constant independent of end purpose.
Here are a few universal truths about building wheels, intended to help one build durable wheels that will stay truer for longer in all kinds of riding conditions.
High Quality Components
High-quality components will generally yield a high-quality wheel relative to a wheel composed of lesser-quality counterparts. Makes sense, right? It’s the old, “garbage in, garbage out” philosophy. Known brands have become known because they have spent the time and effort to engineer, develop and consistently manufacture quality parts.
Different materials have different properties that shake out in real-world ways and engineers spend countless hours obsessing over the most subtle of differences therein. That’s not to say that one can’t build a rideable wheelset with stuff found at a yard sale or in some cool dad’s dusty garage (this is possible), it just won’t ever perform as well as a wheelset that started with modern, high-quality components.
Spoke Length Calculation
At Reserve, every unique rim and hub combination has a carefully-considered theoretical spoke length calculation and a series of practical test builds done to dial in the optimal spoke length specific to the unique geometry of the wheel. The reason this is the case is that spokes of suboptimal length will degrade the trueness of a wheel over time.
In general, spokes that are too short can result in nipple heads being sheared off under load. Spokes that are way too short will result in a wheel that’s literally unbuildable via the threads on the nipples and those on the spokes not being able to engage at all.
Spokes that are too long can result in rim tape being punctured by the spoke end (even if not during the build process, this can happen when the wheel is in radial compliance or deformed vertically under load). Spokes that are way too long can result in an unbuildable wheel; a wheel that is unable to hit the desired tension by way of running out of thread engagement.
So, how does one arrive at the all-important optimal spoke length calculation? It boils down to three things.
First, use at least two online spoke length calculators and average the results before doing the first (yes, first) test-build (see our recommendations below). Averaging the lengths generated by multiple online calculators is likely to get one closer to the optimal spoke length before practical test builds are done.
Recommended Spoke Calculators
https://kstoerz.com/freespoke/
https://www.prowheelbuilder.com/spokelengthcalculator
Second, don’t entirely trust the stock measurements found on the online spoke length calculators. Their math is generally good, but one shouldn’t put ultimate faith in them having accurate measurements for every single hub available in the market, past and present. Instead, measure the hubs accurately yourself using a caliper (or refer to manufacturer generated spec sheets), verify the offset and ERD of the rim and proceed with confidence.
Third, do a practical test build and be ready to change the spoke lengths based on what is observed. A wheel should be on dish and brought up to finished tension before a qualitative judgment is made about spoke lengths. The optimal spoke length may be found on the first practical build per the spoke length calculation(s), more often than not though, the number of practical test builds is greater than one.
Note: While it’s not a good idea to go too far over the recommended tension specification of the spokes (we at Reserve center on 1200 Ncm ± 8%) because this can damage the rim, one does want to bring the tension up to finished tension levels before each de-stressing round.
The below values reflect a tension of 1200 Newton cm ± 95Ncm. 9.81 Ncm = 1Kgf
- ● DT Competition (1.75-2.05mm deflection)
- ● DT Competition Race (1.45-1.65mm deflection)
- ● Sapim Race (1.80-2.10mm deflection)
- ● Sapim D-Light (1.50-1.70mm deflection)
- ● Sapim CX-ray J-bend (0.55-0.72mm deflection)
- ● Sapim CX-Ray Straight-Pull (0.55-0.72mm deflection.
To get an accurate tension reading the measurement must be taken at the middle point of the spoke with a properly calibrated spoke tension meter.
Trailing/Leading Tensioning
On a wheel with crossed spokes, there are trailing and leading spokes. Leading spokes lean forward (at the top of the wheel) and provide stability when pedaling or under neutral load, and resist the torque that is produced when braking force is applied. Trailing spokes lean backward and are pulling the wheel along as torque is applied (the inverse is true when braking).
A common mistake is to add tension to each and every spoke in sequence all the way around the wheel. This will contribute to stubborn hop-stroke. The rim is distorted as tension is added resulting in a localized area on the rim with exaggerated hop-stroke near the first and the last spokes to be tightened as the slack in the rim material aggregates to one area of the rim (akin to the way a balloon will distort when squeezed as the air rushes into the unsqueezed volume).
The best practice is to add tension first to the leading spokes, then the trailing spokes, or vice versa. By doing this, tension is gradually built up along the entire length of the rim and all the pitfalls of localizing the tension in one place are avoided. Here at Reserve, we have hand-drills with some custom square-drive nipple bits that have needle length adjustability (the needle ensures that no more tension is added to the spoke when the spoke end collides with the needle) which we use to ensure consistent tension is added to each spoke during the tensioning process.
The standard practice here is to hand-tighten the spokes on the outside of the high-tension side (disc side for a front, drive side for a rear) just enough that the threads engage. Then add tension (with a drill) to the spokes on the inside of the high-tension side (adding roughly ⅔ of finished tension). After that, drill the spokes on the inside of the low-tension flange, followed by the outside of the loose-side flange. Finally, come back and drill the outside of the high-tension side (the spokes that had been only hand-tightened up until this point).
The above practice–popularized by an excellent wheel builder named Sam Markling–has come to be known as the Markling Method and conforms to the trailing vs. leading protocol. The Markling method isn’t necessary, but it will make the life of the wheel builder much easier than it might otherwise be.
A similar wheel-building process can be done without a drill. In this case, one must remain vigilant with the counting of turns of the spoke wrench as tension is added. The more time that is spent in advance keeping the inputs the same for every spoke, the less time it’ll take to dial the wheel in once desired tension and dish have been achieved.
Repeated De-stressing
The stiffness of a wheel is a function of the materiality of the rim and the tension held in its spokes. As tension is added, the wheel stiffens up, and of course, a wheel needs to be stiff in order to perform well. To preserve a wheel’s tension, ergo its stiffness, one has to de-tension the wheel many times before riding it (the irony is thick).
During wheelbuilding, spokes will wind-up or twist as tension is added. We don’t want spokes with wind-up in the wheels we’re riding because they’ll unwind/de-tension as we’re riding and we’ll lose stiffness in the wheel. Also when riding, spoke heads will settle into place where they rest on the flanges of the hub if J-bend spokes are used.
Anyone who’s completely broken down a wheel will have seen abrasion marks on the flanges of their hub where the spokes have eaten away the finish down to bare metal. Every little bit of settling into place a spoke does will loosen it thereby dropping the tension of the wheel. De-stressing puts the wheel through its paces before it ever makes contact with the ground. By giving the wheel hell right up front and rebuilding it again and again we minimize the likelihood of it failing on the trail. Think of de-stressing rounds as gladiator school for wheels, they’ll be battle tested before they end up on a bike.
The above isn’t an exhaustive list of everything one needs to know in order to build wheels. Rather, these often overlooked details will extend the life of an otherwise well-built wheelset, and hopefully contribute to a more pleasurable riding experience.
About the Author
John Petricciani has been building wheels at Reserve since 2017, starting on the line in the wheel department in the same year. Now he is the main man overseeing all of wheel production at the Santa Cruz, CA HQ but still finds time to hand-build a wheelset or two when things get busy. Since John started in the wheel department we estimate over half a million wheels have been built.
Reserve Road Spoke Length Document
Reserve Mountain Spoke Length Document