05 Apr 2019

Hex drive nipples

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Rear hex drive nipples were designed to handle increased torque but they also prevent builder’s marks on external nipple wrench flats. 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).

What many hex nipples lack is a screwdriver slot. This is important for compatibility with depth-setting nipple drivers, the fastest way to preload nipples to the same depth of thread. That’s why SpokeService specially imported a Sapim hex nipple with this feature. The first photo below shows a collection of adjustable depth-setting drivers that interface with the slot. The black Problem Solvers tool with a 6000 bearing pressed on the end is my daily driver. (If your nipples don’t have a slot, you can start your nipples visually or build a universal tool — both inferior solutions.)

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 may be too deep for everyday use.

10 Feb 2019

Carbon gravel wheels

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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. Please email for help sourcing SON generator hubs.

14 Jan 2019

Nipple penetration

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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. His pictures are correct, however, for all nipples sold here.

09 Jan 2019

Rounding spoke lengths

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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 the nipples sold here can tolerate a couple turns past the end without issue. Either way turning past this threshold causes nipple threads to grind into the unthreaded spoke shank. This causes 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. I generally round to the nearest millimetre. Rounding down by half a millimetre is acceptable when building to high tension (e.g. 125kgf / 1200N) because you can expect spokes to stretch a fraction, notably with lightweight spokes. On a rim brake rear wheel, where tension is quite imbalanced between sides, I 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.

About this series

This is a series about spoke length. These aren’t introductory articles but rather a collection of practical hints. The focus is correct inputs to spoke length calculations — correct input leads to correct output — and how to use outputs. For more general information, see my books list.

18 Dec 2018

Season’s greetings

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This is a reminder for those who may have missed the announcement on Twitter: SpokeService will close on December 24 for the remainder of the year. The time is needed for shop updates, tool service, inventory and reams of government paperwork. On a best-effort basis some orders may ship during this period but no guarantees — place orders now to avoid disappointment.

Happy holidays from SpokeService.