Looking at the hub measurements for Pro 4 and Pro 5 (Boost 6 Bolt), I notice the spoke hole PCD (distance from centre of axle) are no longer the same left and right nor front and rear.
Running the numbers on a spoke calculator, this seems to contribute (along with flange offsets) to now needing 4 instead of 2 different spoke lengths to build a wheelset or to carry as spares.
Pro4 ideally needs 290.6, 291.4, 291.6, and 290.3 - so you can cover it with 291 and 292 without any undersizing and a max oversizing of 0.7. Pro5 ideally needs 290.4, 292.2, 296.3, and 294.9 - seems too far apart for any sharing by rounding.
What possible good reason could there be for this change?
Why generally can't the PCD/offsets be chosen on every hub such that all spokes can be equal length?
The use of double square nips on one side can make wheel builds with just one spoke length possible, I've heard some people using Sapims hm washers on the side with the higher tension to reinforce the spoke hole on non eyeletted rims, that can also help with spoke lengths. Pcd is distance between spokes holes across flange not from axle centre ( edited )
DT hubs seem good for sharing spoke lengths. My 240 exp sp set on xm481 used 1 spoke length.
Using longer DT nipples can help as these are actually threaded longer.
pcd is not what you said it is
I see, it's the diameter so distance between centres of opposite spoke holes. Diagram on the Pro 5 spec sheet is misleading.
I think I would use a 291 and a 295 for that build. There is a guy in Bristol who sells spokes in any length.
Curiosity got the better of me so I checked on my spoke calculator app, there's about a 1mm difference in spoke lengths, I'd get away with using one size of Sapim D-light spokes, (excluding the mullet) it's even slightly better compared to pro4's with my set up.
Oh the joys of brain farts 😂, we've all had our moments.
it’s even slightly better compared to pro4’s with my set up
Interesting, made me double check.
Pro5 ideally needs 290.4, 292.2, 296.3, and 294.9
I messed up, forgot to switch the rear to 32h, so I calculated for 32h front and 28h rear. The last two (rear) numbers should be 291.6 and 290.1. So you can still cover it with two lengths.
Don't worry though, I'm not going to build a wheel myself. Rainy weather get me intro trouble geeking about things I shouldn't.
This remains though - why not at least for the same model hub, design them to have a single length?
Why generally can’t the PCD/offsets be chosen on every hub such that all spokes can be equal length?
design them to have a single length?
Offset rims?