Another wheel day (details omitted).
A customer gave me a Paul rear hub for single-speed bikes.
It's the DISC WORD model with a through-axle width of either 142mm or 148mm, a right-side sprocket seat for either fixed gear or single freewheel, and a 6-hole disc rotor mount on the left.
WORD, to be precise W.O.R.D., is an acronym for Wacky One-Speed Rear Device.
Wacky means "unconventional."
This hub is 142mm width fixed-gear spec, so it works for building a disc road or non-BOOST MTB frame as a single-speed bike.
By my measurement, the left and right flange widths differ by about 0.2mm, with the left being wider. However, since the left end is a nut threaded onto the hub axle, the manufacturer probably intended them to be equal—the slight variance may come from the thread pitch tolerance.
The rim is a 40mm carbon rim with no holes on the outer perimeter except for the valve hole.
Built it.
Paul Disc Word hub, 24H, all CX Sprint, 66-cross lace, no cross-lacing.
This wheel had some complicated issues beyond the usual wheel-building work.
↑This is a shot from inside the rim showing the valve hole orientation before building.
As you can see, this is an offset rim.
↑These are dimensions for a Dura-Ace track large-flange hub with single-threaded axle spec.
With double-threaded spec, flange width is 65.0mm, and since left and right flanges are equal, both would simply be 32.5mm.
With single-threaded spec, Shimano's documentation lists flange width at 75.5mm with offset 5.25mm, but doesn't directly state the actual left and right flange width measurements.
The calculation method for left and right flange width is
"flange width ÷ 2 ± offset."
Actually calculating: 75.5 ÷ 2 = 37.75, so
37.75 ± 5.25 gives us
43mm and 32.5mm.
Naturally, these two add up to 75.5mm.
For a 36H Dura-Ace track rear wheel, keirin regulations require 8-spoke lacing on each side, but even for non-keirin rear wheels, I build them with equal diameter and equal count left and right.
For 32H or 36H non-keirin wheels, one option might be to use equal-diameter spokes with 68-cross or 46-cross lacing—these seem like reasonable compromises that bring spoke deformation more uniformly across left and right compared to equal-diameter, equal-count lacing, offsetting the imbalance from flange width differences.
For Shimano's RS770 disc front hub, the flange width is 59.6mm with offset 6mm, so
↑left and right flange widths come out like this.
For that hub, as you'd expect, I build it with different diameters and different counts—half-CX Sprint 46-cross lacing.
The spoke weight ratio difference left to right is about 13%.
Shimano's offset figure for hub flanges is 5.75mm for single-threaded Dura-Ace track and 6mm for the RS770 front hub—these seem similar in magnitude, but since the RS770 has narrower flange width, the proportional left-right difference for a given offset amount is larger.
For offset hubs, if the narrower flange width is 100%, the wider flange width is about 130% for single-threaded Dura-Ace track and
about 150% for the RS770 front hub.
However, I don't use these figures to decide things like "at 130%, equal-diameter equal-count lacing is fine" or "at 150%, I should do different-diameter different-count to get a spoke weight difference of about 13%."
For fixed-gear rear wheels, I often do full cross-lacing on both sides, which means even with equal-diameter equal-count lacing, the result downplays spoke deformation differences. Because of this, I've never given much detailed thought to whether to add modest different-diameter or different-count elements to offset-flanged fixed-gear hubs.
Earlier I suggested that for single-threaded Dura-Ace track with equal-diameter spokes, something like 32H 68-cross might be a good compromise, but honestly, the 7–8% spoke weight difference with equal-count Comp/CX Sprint might be better.
For the RS770 rear hub, incidentally, flange width is 55.7mm with offset 7.5mm, so left and right flange widths are right 20.35mm and left 35.35mm. With the right flange at 100%, the left is about 170% (173.71%). For that, my usual build is half-Comp 46-cross with a large spoke weight difference of about 21%.
The RS770 front hub lists 59.6mm flange width. When I set calipers to 59.6mm and measure against the actual hub flange, I can confirm that Shimano's specified flange width means outside-to-outside width.
So when using this as the calculation basis, spoke length is strictly "inpoke length." For outpoke, you'd technically measure to the inside of the flange. The difference, though, is tiny compared to spoke thread pitch tolerance—when building with standard 1mm-increment spokes, there's no need to say "the outpoke should be minus 1mm." Besides, with tangent lacing, the spoke path isn't straight once the final cross is woven in. Radial lacing is usually outpoke radial, so you might think to calculate "outpoke length," but again, the difference from inpoke length is small enough that thread pitch tolerance absorbs it comfortably—no need to fuss over it.
Shimano's specs define flange width as outside-to-outside, the same interpretation I use when measuring an unfamiliar hub myself. For Shimano hubs, I trust the spec numbers and use them directly. For Tni hubs, their documentation often lists flange width as center-to-center of the flange thickness, but I ignore that and measure hubs I'm unfamiliar with the same way—using actual measured values.
So here's this hub.
Flange widths are my measured values.
At this scale, calculating spoke length using 35.9mm for both left and right (no offset) presents absolutely no problem.
A 0.2mm flange width difference means the hub body has shifted 0.1mm to the left from no-offset state, so right flange width decreases by 0.1mm and left increases by 0.1mm, creating the 0.2mm difference. So when Shimano talks about offset, they mean the lateral slide of the hub body from the no-offset state.
If the rim were non-offset, I'd have no hesitation about equal-diameter equal-count lacing. But
unfortunately this time the rim was offset.
Measuring showed the rim holes are offset 2.5mm from center.
Here's the critical thing: if you build a rear wheel on an offset rim following the old rule that "the offset direction should be opposite the sprocket side," you end up with a really weird wheel where the gear side has lower tension (strictly speaking, larger spoke deformation). The only real example I know of is Rohloff disc-brake rear wheels. So this time, I oriented the offset rim holes toward the gear side.
The "flange width as a spoke structure" including not just hub offset but also rim offset when the rim is centered on the wheel is shown in the diagram above.
The wider-to-narrower flange ratio falls right between a no-offset hub and a single-threaded fixed-gear hub. This is exactly what I wanted to know. So adding different-count different-diameter lacing risked ending up with less deformation on the left side than right—backward from what you'd want—so I went with all-CX Sprint 66-cross lacing instead.
A customer gave me a Paul rear hub for single-speed bikes.
It's the DISC WORD model with a through-axle width of either 142mm or 148mm, a right-side sprocket seat for either fixed gear or single freewheel, and a 6-hole disc rotor mount on the left.
WORD, to be precise W.O.R.D., is an acronym for Wacky One-Speed Rear Device.
Wacky means "unconventional."
This hub is 142mm width fixed-gear spec, so it works for building a disc road or non-BOOST MTB frame as a single-speed bike.
By my measurement, the left and right flange widths differ by about 0.2mm, with the left being wider. However, since the left end is a nut threaded onto the hub axle, the manufacturer probably intended them to be equal—the slight variance may come from the thread pitch tolerance.
The rim is a 40mm carbon rim with no holes on the outer perimeter except for the valve hole.
Built it.
Paul Disc Word hub, 24H, all CX Sprint, 66-cross lace, no cross-lacing.
This wheel had some complicated issues beyond the usual wheel-building work.
↑This is a shot from inside the rim showing the valve hole orientation before building.
As you can see, this is an offset rim.
↑These are dimensions for a Dura-Ace track large-flange hub with single-threaded axle spec.
With double-threaded spec, flange width is 65.0mm, and since left and right flanges are equal, both would simply be 32.5mm.
With single-threaded spec, Shimano's documentation lists flange width at 75.5mm with offset 5.25mm, but doesn't directly state the actual left and right flange width measurements.
The calculation method for left and right flange width is
"flange width ÷ 2 ± offset."
Actually calculating: 75.5 ÷ 2 = 37.75, so
37.75 ± 5.25 gives us
43mm and 32.5mm.
Naturally, these two add up to 75.5mm.
For a 36H Dura-Ace track rear wheel, keirin regulations require 8-spoke lacing on each side, but even for non-keirin rear wheels, I build them with equal diameter and equal count left and right.
For 32H or 36H non-keirin wheels, one option might be to use equal-diameter spokes with 68-cross or 46-cross lacing—these seem like reasonable compromises that bring spoke deformation more uniformly across left and right compared to equal-diameter, equal-count lacing, offsetting the imbalance from flange width differences.
For Shimano's RS770 disc front hub, the flange width is 59.6mm with offset 6mm, so
↑left and right flange widths come out like this.
For that hub, as you'd expect, I build it with different diameters and different counts—half-CX Sprint 46-cross lacing.
The spoke weight ratio difference left to right is about 13%.
Shimano's offset figure for hub flanges is 5.75mm for single-threaded Dura-Ace track and 6mm for the RS770 front hub—these seem similar in magnitude, but since the RS770 has narrower flange width, the proportional left-right difference for a given offset amount is larger.
For offset hubs, if the narrower flange width is 100%, the wider flange width is about 130% for single-threaded Dura-Ace track and
about 150% for the RS770 front hub.
However, I don't use these figures to decide things like "at 130%, equal-diameter equal-count lacing is fine" or "at 150%, I should do different-diameter different-count to get a spoke weight difference of about 13%."
For fixed-gear rear wheels, I often do full cross-lacing on both sides, which means even with equal-diameter equal-count lacing, the result downplays spoke deformation differences. Because of this, I've never given much detailed thought to whether to add modest different-diameter or different-count elements to offset-flanged fixed-gear hubs.
Earlier I suggested that for single-threaded Dura-Ace track with equal-diameter spokes, something like 32H 68-cross might be a good compromise, but honestly, the 7–8% spoke weight difference with equal-count Comp/CX Sprint might be better.
For the RS770 rear hub, incidentally, flange width is 55.7mm with offset 7.5mm, so left and right flange widths are right 20.35mm and left 35.35mm. With the right flange at 100%, the left is about 170% (173.71%). For that, my usual build is half-Comp 46-cross with a large spoke weight difference of about 21%.
The RS770 front hub lists 59.6mm flange width. When I set calipers to 59.6mm and measure against the actual hub flange, I can confirm that Shimano's specified flange width means outside-to-outside width.
So when using this as the calculation basis, spoke length is strictly "inpoke length." For outpoke, you'd technically measure to the inside of the flange. The difference, though, is tiny compared to spoke thread pitch tolerance—when building with standard 1mm-increment spokes, there's no need to say "the outpoke should be minus 1mm." Besides, with tangent lacing, the spoke path isn't straight once the final cross is woven in. Radial lacing is usually outpoke radial, so you might think to calculate "outpoke length," but again, the difference from inpoke length is small enough that thread pitch tolerance absorbs it comfortably—no need to fuss over it.
Shimano's specs define flange width as outside-to-outside, the same interpretation I use when measuring an unfamiliar hub myself. For Shimano hubs, I trust the spec numbers and use them directly. For Tni hubs, their documentation often lists flange width as center-to-center of the flange thickness, but I ignore that and measure hubs I'm unfamiliar with the same way—using actual measured values.
So here's this hub.
Flange widths are my measured values.
At this scale, calculating spoke length using 35.9mm for both left and right (no offset) presents absolutely no problem.
A 0.2mm flange width difference means the hub body has shifted 0.1mm to the left from no-offset state, so right flange width decreases by 0.1mm and left increases by 0.1mm, creating the 0.2mm difference. So when Shimano talks about offset, they mean the lateral slide of the hub body from the no-offset state.
If the rim were non-offset, I'd have no hesitation about equal-diameter equal-count lacing. But
unfortunately this time the rim was offset.
Measuring showed the rim holes are offset 2.5mm from center.
Here's the critical thing: if you build a rear wheel on an offset rim following the old rule that "the offset direction should be opposite the sprocket side," you end up with a really weird wheel where the gear side has lower tension (strictly speaking, larger spoke deformation). The only real example I know of is Rohloff disc-brake rear wheels. So this time, I oriented the offset rim holes toward the gear side.
The "flange width as a spoke structure" including not just hub offset but also rim offset when the rim is centered on the wheel is shown in the diagram above.
The wider-to-narrower flange ratio falls right between a no-offset hub and a single-threaded fixed-gear hub. This is exactly what I wanted to know. So adding different-count different-diameter lacing risked ending up with less deformation on the left side than right—backward from what you'd want—so I went with all-CX Sprint 66-cross lacing instead.