Hey everyone, I just purchased a set of Giant XCR0 rims and hubs from someone and they sent me a page from the Giant wheel building manual which shows on the rear wheel two different lengths per side. I’ve built a couple sets of wheels now so I have a little experience but I don’t understand how or why there would be 2 different lengths on one side. Can anyone tell me why?
by No_Rush_5540
8 Comments
Cos there’s space for cogs on one side
rear wheels are not usually symmetrical so spoke lengths are different from one side to another to accomadate the cassette.
The “flanges” are not a flat disc like traditional hubs. The front and rear facing holes are separated by about 5 mm or so. Hence the inside spokes (DS an NDS) , have a shorter distance to travel.
The ends of straight-pull spokes don’t share the same plane as j-bend do, so to all intents and purposes there’s gonna be variation in flange to centre measurement for leading and trailing spokes.
It’s the difference between the inner and outer spoke on the lace. Outer spokes (head facing out) take a more direct, slightly shallower angle to the rim nipple. Inner spokes (head facing in) have to cross over or under the outer spokes and end up at a slightly steeper angle, effectively traveling a marginally longer or shorter path to reach the rim.
With straightpull you can do things like that. Perhaps in this case to make insertion clearance for machine building easier. Maybe it makes machining them faster too. Likely reasons like that, just as long as the cost of having extra spoke inventory or rolling complexity is outweighed (and simply passed to the consumer).
Maybe I’m too pessimistic and there’s performance improvements, but I doubt it.
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Giant made proprietary design choices with those hubs. If they look like [this](https://images.bike24.com/media/1020/i/mb/c0/7e/79/giant-xcr-1-30-mtb-carbon-rearwheel-29inch-boost-shimano2-1129315.jpg), the spoke length difference is due to different flange diameters between the inside and outside spoke seats on the same flange. In shop speak, there are two PCDs for one flange.
Traditional straight pull hubs have the same PCD (flange diameter) for leading and trailing spokes, in which case one length per side works great.