8

When a wheel is built with j-bend spokes, they are typically "interlaced", as the picture from ParkTool shows (crossing #3): Interlacing picture by ParkTool

There are clear technical advantages of doing so, described in Jobst Brandt's "The Bicycle Wheel" and asked here previously.

But I have never seen straightpull spokes being interlaced. As a random example, here's a picture of a Shimano straightpull wheel not interlaced:

Shimano straightpull wheel

Is there a reason for this? I don't see how straightpull spokes/hubs are different in this respect, and IMO the same advantages of interlacing would apply.

Improve this question
1
  • On my DT Swiss PR 1400 DICUT® OXiC rear wheel the spokes are interleaved and creaking like hell. I had to put tape between the spoke crossings to silence them. I checked the tension, it’s ~1200N on the drive side, so high enough. I think they are only barely touching (compared to a traditional 3 crossing J-bend wheel) which makes it worse.
    – Michael
    Commented Jan 29 at 10:28

2 Answers 2

Reset to default
10

I think straight-pull spokes don't have a problem with negative loads the same way j-bend spokes do.

For j-bend spokes, any push-force incurred by rim flex would force a non-interlaced spoke into substantial buckling and twisting. It is substantial because if the spoke started out perfectly straight, there is initially no direction it could move to take up any approach of the nipple towards the hub, the spoke first needs to deform into a new buckle that can then start to take up the slack. Juhist's answer discusses this in some more mathematical detail.

It is this motion that causes the nipples to loosen. Interlacing "solves" the problem by forcing every spoke into a little pre-buckle, which gives them a well-defined direction into which to deform when slack needs to be taken up. It's a big ugly hack, but it mostly avoids twisting that would unscrew the nipple.

Straigh-pull spokes solve the problem in a much better way: they allow the spokes to simply move inwards at the hub when necessary (in a way the j-bend prevents, counter-productively). Movement at the hub is harmless as there's no screwed thread at that end.
As a secondary advantage, the perfectly straight spokes make the wheel stiffer by way of being more rigid in the tensile direction, which prevents the wheel from flexing as much in the first place.

Improve this answer
12
  • 1
    I'd like to see such video. There are straightpull hubs (e.g. ones used in Mavic Ksyrium, mavic.com/en-us/p/ksyrium-sl-disc-rr1244?variant=262) which would just release the spoke which is about to bulge.
    – Konstantin Shemyak
    Commented Jan 28 at 16:32
  • 1
    Can't remember what was the video I had in mind, but you can certainly see it in some of the classic "hucked to flat" ones. E.g. here: youtu.be/mUyhR62yNeQ?si=rIpWJS1HIA5M4yYh&t=174 You might say this is an extreme test, but actually it's relatively harmless as far as the wheel is concerned because the impact is centered. The footage I remember showed the sideways motion, which is where most of the spoke-buckling happens.
    – leftaroundabout
    Commented Jan 28 at 16:47
  • 1
    I don't see spokes bulging in the linked video.
    – Konstantin Shemyak
    Commented Jan 28 at 19:04
  • 1
    @KonstantinShemyak I have a pair of Mavic Allroad UST (the entry-level to the range), they have straightpull spokes and there is a contact. I also have have a pair of Allroad S (second tier), that features the same hub/design as the Ksyrium SL you linked. DT Swiss on the other hand seems to have interlacing on all their range (example from a high end XC wheel dtswiss.com/itc/00/00/00/00/00/00/00/00/70/00/11/25/8/…) So hard from that sample to draw conclusions.
    – Rеnаud
    Commented Jan 29 at 13:20
  • 1
    @Renaud Thanks for the example (with picture) of an interlaced straightpull wheel! The fact that such thing exists makes me think that vendors don't interlace their wheels just because it's easier not to do it, although it would be beneficial for the wheel strength and durability.
    – Konstantin Shemyak
    Commented Jan 30 at 15:21
2

Recently I have seen a few straight-pull wheels built with interlaced spokes, both in real life and as product images. The last example is the new SON dynamo hub (image from the product site): SON dynamo hub It looks like there is no technical reason to not interlace. Benefits are the same as with J-bend spokes. The price reason is that a non-interlaced wheel is a bit easier to build, and it seems to often win over the wheel's longer life.

Edit: maybe a better picture, another random product image from the net: wheel with straightpull spokes interlaced

Improve this answer
3
  • It's a bit strange to me conclude that the "cost cutting" measure applies to the upper range products. "Generalisation by example" is dangerous, but for Mavic for example, contactless spokes are advertised as a feature of the upper ranges. I'm also under the impression that contactless spokes mostly exist in wheelsets that use proprietary parts, which a way to ensure that only parts meeting certain specifications are used.
    – Rеnаud
    Commented Aug 7 at 6:20
  • @Rеnаud Another example when a solution which is inferior for reliability but popular (and sometimes marketed) on high-end products is radial lacing.
    – Konstantin Shemyak
    Commented Aug 20 at 9:34
  • 2
    Radial is also used on the cheapest Shimano and Campagnolo wheelsets that cost 140€ (front and rear). My point was that you design things differently if you design a "system" rather a components that needs to work with components that you have no control on. Upper (aluminium) Mavic wheels for example use proprietary nipples threaded into the rim (M7), and locked by thread locker. So they don't have the issue that an unloaden spoke can cause the nipple to unscrew. By giving up interlacing, they win compliance which a desired trait for off-road bikes.
    – Rеnаud
    Commented Aug 20 at 10:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.