Straight-pull spokes - worth it?

Question

Straight-pull spokes have been around for awhile on MTB wheels, but mainly just on very expensive wheelsets (Mavic Deemax for example). Recently the better wheel component manufacturers have been getting in on this by selling straight-pull spokes and compatible hubs individually, and they are generally considerably more expensive than the 'normal' variety.

However in my many years of snapping spokes they have never snapped at the elbow (the 'weak' point straight-pulls are supposed to address), they always break in the centre - presumably because the double-butting process has moved the weak point there.

So my question is this: Are straight-pull spokes worth it, or are they another expensive marketing gimick to solve a problem that doesn't exist?

Answer 1

This is debatable, but since you asked, here go my cents:

A wheel has three "parts": rim, hub and spokes.

Spokes have two functions:

1. Sustain the vertical forces on the wheel (weight of the rider, landing, etc.);
2. Transmit torque while accelerating (rear wheel only) and braking;

Any properly laced wheel will do it, but there are many ways to design the connection of the spokes to the hub, or to the rim. These manufacturers have chosen to make the spokes "elbowless", which could result in less chance of failure, and could result in other side-benefits, like flangeless hubs, or fancier-looking wheels.

I'd much rather use standard components only, since they are easily replacable and swappable. I sometimes damage some rim, then I can change the rim only, because the nipple-hole connection is standard. I also can change the hub if needed, because the flange-elbow connection is standard. In the other hand these fancy wheels are proprietary, and you have only a single source of spare parts, which tend to be VERY expensive and sometimes are not available on the shelf.

As a bottomline, my spokes tend to break at the elbow, rarely at the thread end. I don't use butted spokes, so that could make some difference. Recently, I had some breakages at the mid-length, but I suppose this is due to excessive weight per wheel (tandem) and sub-optimal quality spokes.

Final thought: I would only spend big in such a wheel if I have a very well-defined reason. These are made for racing, and for anyone who doesn't race (and isn't sponsored), I'm pretty sure the cost is too much for the benefit.

Answer 2

Yes, straight pull spokes are technically superior to traditional J-bend spokes. The only reason that J-bend spokes are relatively more popular is because it's cheaper to machine a hub with simple flanges on a lathe. Well-designed straightpull hubs typically cost more.

Note that a straight-pull spoke in generally can and should be tensioned higher than the equivalent J-bend spoke. As always, build quality is key, and the average bike shop won't necessarily have the experience to do it well. Nevertheless, in comparison to a J-bend, a straight pull spoke properly assembled onto a properly designed hub will:

1. Not fatigue as fast -- especially if a J-bend is not kept adequately tensioned. in other words, a straightpull spoke will not relax as quickly.
2. Eliminate spoke rubbing typical in most traditionally laced wheels.
3. be stiffer radially AND laterally than most traditional lacing for the same spoke gauge (though it is hard to do a direct comparison because hub and rim geometry varies widely)
4. Be lighter for the equivalent capability -- or, more importantly, will have less inertia due to the ability to use fewer spokes and/or narrower gauge butted spokes with no loss in stiffness & strength
5. Will last longer -- the J-bend spoke beds in, then frets and ovalizes the spoke hole, losing tension as the wheel wears in, as well as wearing out the hub. In a straightpull spoke, there is much less motion & wear at the hub and nipple.

Bottom line: straight pull spokes, properly designed and built, will be lighter, stiffer, and require less truing than a conventional wheelset with the same number of spokes.

What are the advantages of J-bend spokes? Price and parts availability.

Answer 3

Engineering aside, there is one huge advantage to straight spokes: you can always replace a spoke without ever having to take off the cassette or disk rotor. This is awesome.

The matching huge disadvantage is that you won't be able to afford (or find) replacement spokes, so the ease of replacing them is entirely academic.

One other disadvantage is that when you're tensioning them they tend to spin when you turn the nipple, so unless you want to carry a big-arse pair of pliers with you to hold the spoke and stop it spinning, forget about being able to do a roadside repair.