Wheels again today (and so on).
The other day I rebuilt the front wheel with a Shimano WH-7900 hub and a Euorus (vintage aluminum-spoke rim) rim, and now I'm building its matching rear wheel.
Not that it really matters, but I call the steel-spoke era EUROURUS "Eeroas" and the aluminum-spoke version "Euorus," but since explaining that seemed like a hassle, I just wrote "Euorus" when talking about the front rim.
With the WH-7900 hub, only with the C24 rim does the left flange and the left end face of the hub shell sit nearly flush (meaning the flange is wider), but with the C35 and C50, they're set in a bit from the edge.
I borrowed these images from a blog called Nomu Lab Diary from about 13 years ago. When I search for wheel info, I keep running into that blog, but honestly, everything that guy writes about, I already know, so it often just gets in the way of my research.
↑Freewheel side
↑Non-freewheel side
The spokes were laced with different diameters left and right. The WH-7900 rear wheel has the C24 and C35 laced with different diameters left and right, and only the C50 is laced with the same diameter both sides.
With the WH-7900 rear wheel, depending on whether the rim is CL, TL, or TU, the spoke lengths on the left and right can be the same, differ by 1mm, or differ by 2mm.
For example, with C24-CL, both sides are 302mm, but since they're different diameters left and right, the spoke part numbers differ. With C24-TL, it's 304mm and 306mm with different diameters left and right. With this C35-TU, it's 294mm and 295mm with different diameters left and right. With C50-TU, both sides are 278mm with the same diameter, so the spoke part numbers are the same on both sides.
With prebuilt wheels, there are cases where even if they use the same number of spokes laced with different diameters left and right, or different numbers of spokes laced with reversed different diameters, as rim height increases, they switch to the same number laced the same way both sides.
Besides this case where the WH-7900 only doesn't use different diameters left and right on the C50, Rovar's CLX32 rim brake wheels have reversed different diameters laced on the rear, but when Rovar's rim height gets to 38mm or higher (C38 or CLX40), they switch to the same diameter laced both sides. Also, in a discontinued Colima model where the model name itself refers to the rim height at 32, 47, and 58, there's a prebuilt wheel (12+8H) laced not 2:1 but in a 3:2 ratio, and among these, only the 32mm high rim "32" is laced with reversed different diameters. With Colima, the spokes used in prebuilt wheels are only CX-RAY or CX, which in terms of spoke weight proportion are around 65% and around 100%, so the difference in spoke weight ratio is quite extreme.
I think left/right different diameter or reversed different diameter lacing is effective regardless of rim height. The reason prebuilt wheel makers stop doing it as rim height increases is probably—well, I have my suspicions. It touches on my money-making secret, so I won't write it here.
If Shimano noticed the effectiveness of different diameter lacing by the time of the WH-7900, then with the WH-9270 two generations later, they should have done it on both front and rear wheels—the wheel is regressing! Do it on the C36 at least, regardless of the C50 and C60. When we rebuild the C36 and C50 front and rear wheels in our shop, people say nothing but "it's a completely different beast" (though the tangential lacing probably factors into that too). That's what I thought, but then one thing occurred to me: what if Shimano's boundary line for whether to use different diameter lacing is between C35 and C36? That would explain everything. At 35mm rim height, different diameter or reversed different diameter lacing is effective. At 36mm rim height, whatever drawbacks there are must outweigh the benefits—that's the conclusion Shimano must have reached internally.
Then there's the WH-9000 after the WH-7900. The C35, C50, and C75 rear wheels use Shimano's 2:1 Optavar with flat spokes equivalent to 2.0-1.8-2.0mm, laced with the same diameter both sides. The C24 CL and TL are not Optavar but are laced the same number both sides, but unlike the 7900, they use flat spokes equivalent to 2.0-1.5-2.0mm, laced with the same diameter both sides—which theoretically is inferior. And with the C24 tubular WH-9000-C24-TU, not only is it 14+7H Optavar instead of 10+10H with the same number both sides, but—get this—it's laced with reversed different diameters using both 2.0-1.5-2.0mm equivalent and 2.0-1.8-2.0mm equivalent flat spokes!
If the person who pushed this spec through had gotten Shimano to use different diameter or reversed different diameter lacing on both front and rear wheels for the WH-R9270, that would have been great. But that's just not how Shimano works.
I rebuilt it with the rim from Nomu Lab Wheel No. 1. As for the rim stickers, since the front wheel's Eeroas one is still there and the owner said it'd be more interesting to leave them on, I've left them as-is.
The freewheel side spokes are black Champion 14-gauge plain, with the final cross not laced through.
The non-freewheel side is black CX Sprint with the final cross laced through. But for now, I'm not doing any tangential lacing.
Bonus
I initially got pretty far building it with CX Sprint on the freewheel side and CX-RAY on the non-freewheel side, but that would've given me a wheel with about the same stiffness as before the rim swap. While the added weight in the spoke section is barely noticeable, the increased stiffness from that change is something you can feel a real difference in. Plus, the rim itself getting heavier is the far bigger factor when it comes to overall weight. With 20 spokes, I went with different diameter lacing at roughly 100/78% spoke weight ratio.
If it were 24H, I'd be using CX Sprint and CX-RAY with tangential lacing on the non-freewheel side.
The other day I rebuilt the front wheel with a Shimano WH-7900 hub and a Euorus (vintage aluminum-spoke rim) rim, and now I'm building its matching rear wheel.
Not that it really matters, but I call the steel-spoke era EUROURUS "Eeroas" and the aluminum-spoke version "Euorus," but since explaining that seemed like a hassle, I just wrote "Euorus" when talking about the front rim.
With the WH-7900 hub, only with the C24 rim does the left flange and the left end face of the hub shell sit nearly flush (meaning the flange is wider), but with the C35 and C50, they're set in a bit from the edge.
I borrowed these images from a blog called Nomu Lab Diary from about 13 years ago. When I search for wheel info, I keep running into that blog, but honestly, everything that guy writes about, I already know, so it often just gets in the way of my research.
↑Freewheel side
↑Non-freewheel side
The spokes were laced with different diameters left and right. The WH-7900 rear wheel has the C24 and C35 laced with different diameters left and right, and only the C50 is laced with the same diameter both sides.
With the WH-7900 rear wheel, depending on whether the rim is CL, TL, or TU, the spoke lengths on the left and right can be the same, differ by 1mm, or differ by 2mm.
For example, with C24-CL, both sides are 302mm, but since they're different diameters left and right, the spoke part numbers differ. With C24-TL, it's 304mm and 306mm with different diameters left and right. With this C35-TU, it's 294mm and 295mm with different diameters left and right. With C50-TU, both sides are 278mm with the same diameter, so the spoke part numbers are the same on both sides.
With prebuilt wheels, there are cases where even if they use the same number of spokes laced with different diameters left and right, or different numbers of spokes laced with reversed different diameters, as rim height increases, they switch to the same number laced the same way both sides.
Besides this case where the WH-7900 only doesn't use different diameters left and right on the C50, Rovar's CLX32 rim brake wheels have reversed different diameters laced on the rear, but when Rovar's rim height gets to 38mm or higher (C38 or CLX40), they switch to the same diameter laced both sides. Also, in a discontinued Colima model where the model name itself refers to the rim height at 32, 47, and 58, there's a prebuilt wheel (12+8H) laced not 2:1 but in a 3:2 ratio, and among these, only the 32mm high rim "32" is laced with reversed different diameters. With Colima, the spokes used in prebuilt wheels are only CX-RAY or CX, which in terms of spoke weight proportion are around 65% and around 100%, so the difference in spoke weight ratio is quite extreme.
I think left/right different diameter or reversed different diameter lacing is effective regardless of rim height. The reason prebuilt wheel makers stop doing it as rim height increases is probably—well, I have my suspicions. It touches on my money-making secret, so I won't write it here.
If Shimano noticed the effectiveness of different diameter lacing by the time of the WH-7900, then with the WH-9270 two generations later, they should have done it on both front and rear wheels—the wheel is regressing! Do it on the C36 at least, regardless of the C50 and C60. When we rebuild the C36 and C50 front and rear wheels in our shop, people say nothing but "it's a completely different beast" (though the tangential lacing probably factors into that too). That's what I thought, but then one thing occurred to me: what if Shimano's boundary line for whether to use different diameter lacing is between C35 and C36? That would explain everything. At 35mm rim height, different diameter or reversed different diameter lacing is effective. At 36mm rim height, whatever drawbacks there are must outweigh the benefits—that's the conclusion Shimano must have reached internally.
Then there's the WH-9000 after the WH-7900. The C35, C50, and C75 rear wheels use Shimano's 2:1 Optavar with flat spokes equivalent to 2.0-1.8-2.0mm, laced with the same diameter both sides. The C24 CL and TL are not Optavar but are laced the same number both sides, but unlike the 7900, they use flat spokes equivalent to 2.0-1.5-2.0mm, laced with the same diameter both sides—which theoretically is inferior. And with the C24 tubular WH-9000-C24-TU, not only is it 14+7H Optavar instead of 10+10H with the same number both sides, but—get this—it's laced with reversed different diameters using both 2.0-1.5-2.0mm equivalent and 2.0-1.8-2.0mm equivalent flat spokes!
If the person who pushed this spec through had gotten Shimano to use different diameter or reversed different diameter lacing on both front and rear wheels for the WH-R9270, that would have been great. But that's just not how Shimano works.
I rebuilt it with the rim from Nomu Lab Wheel No. 1. As for the rim stickers, since the front wheel's Eeroas one is still there and the owner said it'd be more interesting to leave them on, I've left them as-is.
The freewheel side spokes are black Champion 14-gauge plain, with the final cross not laced through.
The non-freewheel side is black CX Sprint with the final cross laced through. But for now, I'm not doing any tangential lacing.
Bonus
I initially got pretty far building it with CX Sprint on the freewheel side and CX-RAY on the non-freewheel side, but that would've given me a wheel with about the same stiffness as before the rim swap. While the added weight in the spoke section is barely noticeable, the increased stiffness from that change is something you can feel a real difference in. Plus, the rim itself getting heavier is the far bigger factor when it comes to overall weight. With 20 spokes, I went with different diameter lacing at roughly 100/78% spoke weight ratio.
If it were 24H, I'd be using CX Sprint and CX-RAY with tangential lacing on the non-freewheel side.