20 Jun 2017

Measuring ERD

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If you have the wrong effective rim diameter (ERD), there’s a good chance you’ll compute the wrong spoke length. A lot of times you can use values from the manufacturer but it’s best to double check the numbers with Google. After a while you’ll find some brands, like Stan’s NoTubes or WTB, are very reliable in their ERD numbers (contact me to order Stan’s rims).

You’ll get the most accurate ERD numbers if you measure your rims so I always do. 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. 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. It’s worth counting to make sure you’re not off by one. Pull the spokes tight across a ruler with 0.5mm resolution (such as this one). For most builds the spokes will overlap on the ruler, in which case you deduct the overlap distance from 600mm. If the spokes don’t overlap, add the gap distance to 600mm. Perform at least two measurements 90° apart and average the results to get ERD.

If you’re building with nipple washers, remember to increase spoke length to compensate. As an alternative, you can simply install nipple washers on your measuring spokes and build nipple washers right into your ERD. With this direct approach, no compensation is required.

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, don’t round down aggressively for low tension builds or on the low tension side of a wheel. When shopping here, you get to round to the nearest millimetre compared to traditional vendors that stock spokes in two millimetre increments. In a followup blog I’ll expand on the topic of rounding, which matters more when available lengths aren’t as good. Stay tuned.

31 May 2017

Rims for new builders

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Sometimes newbies ask about cheap rims to try wheelbuilding, something of a contradiction in a question. It’s thinking about the cost of failure versus the experience and rewards of success. 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 (but don’t go nuts with heavyweight spokes either). Buy a quality rim with the attributes you want to ride and you’ll do fine.

09 May 2017

Carbon tubular time

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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 completely disagree. 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.

26 Apr 2017

Carbon for the people

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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!

15 Apr 2017

Road tubeless continued

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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.