Hex drive nipples

April 5, 2019

Rear hex drive nipples were designed to handle increased torque but they also prevent builder’s marks on external nipple surfaces. Some people like rear drive because the turning direction is intuitive — clockwise is tighter. Since the external interface exists just the same, you can forget the rear hex drive if you prefer (or treat it as a backup to save the day if a nipple cracks or rounds off).

The Sapim hex drive is 5.5mm. It’s a balance between making the interface as large as possible while leaving room for tool clearance at the rim holes. Even so a thinwall tool is often necessary. I have three in my toolbox. My main tool is the Park SW-15, a 3-way that fits nicely in the hand and provides good leverage. Blue tape marks the 5.5mm end. The Park Tool SW-18 is a screwdriver design, which reaches into deeper rims and may fit better in race toolboxes. The Sapim factory tool is excellent quality and handles even deeper rims but too deep for everyday use.

Carbon gravel wheels

February 10, 2019

This is a sweet set of 650b gravel wheels. They’re put together using Onyx rear and SON front hubs paired with Light-Bicycle carbon rims. These wheels are destined for a year-long journey so I’ve selected Sapim Force spokes, which makes builds more bulletproof. For more casual use lighter spokes would definitely work.

Nipple penetration

January 14, 2019

The talented Karl Stoerz published a pictorial discussion of thread penetration, a helpful supplement to my last post. I agree with Karl but point out his pictures apply to most but not all nipples — it’s always useful to check yours to avoid surprises. Some nipples bottom out before the spoke can penetrate past the end at all.

Rounding spoke lengths

January 9, 2019

The correct spoke length is one that penetrates the nipple just right — not below the screwdriver flats and not past the top of the nipple. You don’t want to go too short because spoke threads reinforce nipples internally. Nipples, particularly aluminum nipples, have higher failure rates when paired with short spokes. You don’t want to go too long either. I define too long as past the end of the nipple. This is strictly true for some nipples however many can tolerate a couple turns past the end without issue. Turning past this baked-in limit causes nipple threads to grind into the unthreaded spoke shank, which creates a weakness in the spoke and is associated with spoke breakage.

The rounding part

Spoke length calculators output lengths to the tenth of a millimetre, which must be rounded to match available supply. There’s no universal rounding algorithm because it depends on how you calculate spoke lengths in the first place. It depends on ERD measurement technique.

In my process I use measuring tools based on theoretical spoke penetration to the bottom of the nipple screwdriver slot. I don’t want my actual spoke penetration to be short of this mark, so I’m cautious about rounding down. My baseline is rounding to the nearest millimetre. If my target tension for a spoke is high, say 125kgf / 1200N, I’m not bothered rounding down as much as 0.6mm. This is because spokes stretch a fraction under tension and stretch is more pronounced at high tension. This logic particularly applies to thinner spokes because thinner spokes are more elastic. The opposite holds as well — a spoke built to 60kgf could be rounded up 0.6mm. As an example when building a rim brake rear wheel, where tension is quite imbalanced between sides, a wheelbuilder might round up on the low tension side and down on the high tension side if both lengths are halfway between sizes.

(Hopefully you can see this rounding logic doesn’t make sense if your theoretical spoke length targets the end of the nipple. In that case you would rarely round up.)

Traditionally spokes are stocked in two millimetre increments, which invites compromises depending on your calculated lengths. You can be forced to reckon with the the risks of going too short or too long. Maybe the uncertainty steers you to brass nipples instead of aluminum. Maybe it causes you to pick up nipple washers as an insurance policy. Bottom line: it’s not doing you any favours and to build the best wheels you ought to shop in one millimetre increments.

Industry Nine fat wheels

December 17, 2018

Some parts of Canada call for a different approach to winter riding. These wheels are the full fat approach, marrying Industry Nine fat hubs to DT Swiss BR710 rims. The hubs are 142×15 in the front and 177×12 in the rear.

Spoke length

These rims are a good example of ERD issues discussed in my last blog. The DT Swiss rim decals include technical information stating ERD to be 549mm. I like that but it doesn’t change my process — I measured them anyway getting 547 on the front and 546 on the rear. To add intrigue the DT Swiss spoke length calculator lists 547 for this rim. Going my own way resulted in perfect penetration, a hair below the top of the nipple in each case. With single wall rims you want to be more fussy about spoke length, particularly avoiding penetration past the top of the nipple.

ERD seriously

November 27, 2018

There are two ways ERD goes wrong.

First there are variances in rim manufacturing. Some manufacturers are better than others and to some extent you get what you pay for. But I always measure and frequently find rims out of spec or find differences between pairs of identical rims. If you know what you’re working with, variances are no big deal. If you input correct dimensions, you’ll get correct spoke lengths.

The second issue is differing definitions of ERD. Typical definitions include penetration of the spoke into the nipple head, which is important for maximum strength. But how far the spoke extends beyond the nipple seat (into the rim) is unclear. It depends on nipple geometry and encodes some preference for how much penetration is ideal. In other words ERD is relative to an undisclosed nipple and opinions regarding its use.

Typically the magnitude of these errors is pretty small, maybe 0.5mm each. Additional error is introduced when you round spoke lengths to match availability (why buying spokes in 2mm increments is rough). Maybe these errors add up to a problem and maybe they cancel each other out.

This sounds like a pain but it’s not at all. You simply make your own tools and take your own measurements. The parts cost next to nothing, assembly takes 10 minutes and you’re left with tools you can use forever. Maybe it seems like a pain because you want your spokes and rims to arrive at the same time. That’s fair but getting it right the first time is always fastest.

Coaxial SON

October 28, 2018

SON hubs and lights include normal spade connectors — trim wires to length, crimp on connectors and connect to your hub. Anyone can manage this system and it works well. As an upgrade, SON offers a coaxial version that I put together today. This system requires more effort to assemble (basic soldering required) but pays you back with a number of advantages.

The upgrade comes with an adapter that connects a coaxial plug to the hub spade connectors. The new plug interface is spring-retained, which is more refined than the friction fit of spade connectors. The coaxial plug is secure but can be fitted or removed with full-fingered gloves.

Using beefy spokes

May 30, 2018

The typical spoke decision is between straight gauge and some double-butted model. For conditions outside the bell curve, there are two specialty models.

Sapim Force is a triple-butted spoke with a 2.18/1.8/2.0mm profile. They are similar to Sapim Race with a little more meat on the vulnerable elbow section. There is a cost penalty but weight and stiffness are about the same. Fatigue life is better — if you’ve been burned by broken elbows, Force might be the ticket. I often use Force on touring and bikepacking wheels to work with 32 spoke wheels when 36 might be more conventional (opening up more choices for hubs and rims).

Sapim Strong is a single-butted spoke with a 2.3/2.0mm profile. These are the biggest bicycle spokes I use and I stop at this gauge because it’s the biggest spoke that works with regular 2.0mm nipples. Strong shares the massive stiffness of Sapim Leader but has a serious amount of extra material on the elbow. People use Strong for e-bikes, cargo bikes and the heaviest touring applications. For regular day-to-day use they’re overkill though I’ve used them for riders >400 pounds.

Hope is a strategy

April 29, 2018

Hope hubs don’t have the tightest geometry or the lowest weight, but they’re solid kit for the money. Here are a couple of Hope wheelsets built this month — you might see them on the road in different parts of Alberta.

Tutorial video

March 15, 2018

Gerd Schraner, veteran wheelbuilder and author of The Art of Wheelbuilding, produced a two-hour instructional DVD called Mastering the Wheel. Now you can go to school on YouTube:

RIP Gerd.