Measuring ERD

June 20, 2017

Pros measure the effective rim diameter (ERD) of every rim.

My tools are DIY, which is inexpensive. Here’s how I make them: take two black 310mm Sapim Leader spokes and cut off the elbow leaving a 300mm rod. Use bolt cutters or a hacksaw to get close, then creep up on 300mm exactly using a file or a grinder. Screw a silver nipple to each rod using a bit of Loctite so they never move. For my process I make sure the spoke penetrates the nipple until it’s flush with the bottom of the screwdriver flats — spokes stretch a little under tension so they’ll end up in a good place. That’s it. If you’re precision-minded, you can ensure nipple geometry isn’t a factor by making a new set of measuring rods any time you build with a new variety of nipple.

Usage is straightforward. Insert your measuring spokes into opposing spoke holes, counting them to make sure you’re not off by one. Pull the spokes tightly across a ruler. To make the process easier and more accurate, try raising the ruler with a shim so the spokes leave the rim closer to 90°. Use a ruler with 0.5mm resolution (such as this one) or eyeball to the same. For most builds the spokes will overlap on the ruler, in which case you deduct the overlap length from 600mm. If the spokes don’t overlap, add the gap length to 600mm. Perform at least two measurements 90° apart and average the results to get ERD.

Note: you don’t need 300mm spokes to make a tool but it makes the addition/subtraction less error-prone. Use what you have but adjust the arithmetic factor to the sum of the length of your rods. If by some trick you end up with 300mm and 299mm rods, carry on using 599mm in your calculations instead of 600mm.

If you’re building with nipple washers, remember to increase spoke length to compensate. As an alternative, you can install nipple washers on your measuring spokes and build nipple washers right into your ERD. With asymmetric washers it’s helpful to give your measuring spokes a spin after pulling them taut just to make sure everything is seated properly. Overall this approach accounts for the end-to-end nipple/washer/rim fit and avoids errors from incorrect nominal measurements (a real thing).

Most spoke calculators will give you lengths to the tenth of a millimetre, which you’ll need to round to the nearest available length. Since measuring as above targets the bottom of the acceptable range, resist rounding down for low tension builds or on the low tension side of a wheel. In a future blog I’ll expand on the topic of rounding.

Rims for new builders

May 31, 2017

Sometimes newbies ask about cheap rims to try wheelbuilding, which isn’t the right way to think about starting. Rim quality sets the stage so inexpensive rims may serve to frustrate more than anything. If you’re apprehensive about wheelbuilding, and there isn’t any reason to be, stay away from ultralight rims and low spoke count rims. Stay away from ultralight spokes. Buy a quality rim with the attributes you want to ride and you’ll do fine.

Carbon tubular time

May 9, 2017

This is another build using China-direct carbon rims. These are tubulars from Light-Bicycle, a brand featured on this blog a few times. They’re nice rims. The new infosheet from LB says special skills are required to build carbon rims but I can’t agree. If you’re smart enough to use a tensiometer, you can build carbon. I like nipple washers with carbon but otherwise my process is the same.

Carbon for the people

April 26, 2017

A recent build using economical carbon rims from Light-Bicycle. I selected Sapim D-Light spokes and aluminum nipples to save weight without compromising durability. Came out great!

Road tubeless continued

April 15, 2017

White Industries T11 hubs mated to Stan’s Alpha 400 rims is a combination I’ve built (and ridden) in more than one incarnation. This set is put together with Sapim Laser spokes in the front and rear non-drive side, Sapim Race rounding out the rear. That puts total weight a hair over 1500 grams while remaining stiff enough for the rider. These wheels are setup tubeless with Stan’s tape and valves supporting Schwalbe Pro One tires in 700×28. A perfect combination top to bottom.

Wheelbuilding link

March 26, 2017

Thanks to Ric from Wheel Fanatyk for scanning a series of articles on wheels and wheelbuilding. They cover a lot of ground that will interest wheelbuilders new and old. Download in PDF.

Fancy carbon

November 1, 2016

It was a pleasure building these fancy WTB CI31 rims to DT Swiss 350 hubs. Normally I find myself building China-direct carbon rims but the brand name stuff is great too.

Mitigating spoke windup

September 10, 2016

One challenge a wheelbuilder faces is managing spoke windup. Windup happens when friction between spoke and nipple causes the spoke to twist instead of tightening. This is bad because a twisted spoke is not in equilibrium and will eventually unwind. When twisted spokes unwind, wheels lose alignment. Windup worsens as spoke diameter decreases, which makes thin spokes like DT Revolutions more difficult (thicker spokes build more easily). The problem worsens as tension increases, which is a bigger issue in the 11-speed era because higher tensions are typically required.

There are a few strategies for dealing with spoke windup. The first and most fundamental is to make sure nipples receive ample lubrication. Sometimes adding more lubrication during a build helps. The second strategy is to detect spoke windup and compensate. Windup can be detected by feeling the spoke rotate in tandem with turns of the nipple (a flag can be fixed to the spoke to provide a visual cue). When you start experiencing spoke windup, it’s helpful to overturn the nipple and then back off. For example to achieve a quarter turn of the nipple, tighten the nipple a half turn then loosen by a quarter turn. Windup is released during the loosening step.

Before a wheel is declared complete it should be free of windup. Windup can be freed by flexing spokes in different ways. One way is to grab roughly parallel pairs of same-side spokes and pull them together. A more drastic method is to put the wheel on the ground, touch the ground with the hub and press down around the rim. You can often hear pinging noises as spokes unwind. A wheel is complete when these procedures do not change the wheel and other tolerances are met.

Brass or aluminum

August 1, 2016

The choice of nipple material inspires zealotry — some prefer brass, some prefer aluminum, others a mix of materials. Brass nipples are more popular because they’re cheaper, stronger and more corrosion resistant. Aluminum nipples feature superior finishes at one third the weight. How to choose? If you’re hard on gear, clean infrequently or ride in adverse conditions, then brass is a sensible choice. For scenarios where weight and performance matter, aluminum is the way to go.

Working with aluminum nipples shouldn’t inspire fear — in fact many find aluminum nipples turn more smoothly. How do pros work with aluminum? First, use liberal lubrication. When building in the first place, make sure threads are fully covered with oil or other spoke preparation compound. When making adjustments down the road, dribble a thin oil into the nipple and into the rim at the base of the nipple. Second, avoid stressing aluminum nipples by using a 4-sided spoke wrench (e.g. Park Tool SW-40). Compared to a regular 3-sided wrench, a better tool distributes forces more evenly. If your nipple has a secondary interface on the rear, that’s a safe way of applying torque too. Last buy quality aluminum nipples. For example Sapim nipples are made of 7075 aluminum, a stronger alloy that is not the industry norm. Sapim anodizes silver nipples for corrosion resistance whereas other makers ship these raw. From a quality perspective aluminum nipples are less interchangeable across brands.

Asymmetric rims

May 15, 2016

This build used DT Competitions to lace Hope Pro4 hubs to WTB Asym rims, in this case a 650b (27.5″) wheelset. Asymmetric rims aren’t strictly new but the number and variety of models on the market is improving. The idea is simple — spokes land to one side of the rim instead of the centre. This counteracts the natural asymmetry in rear wheels, resulting in more even tension. I’m a fan.