Tomm Willians

On the verge of ordering a new set of Dt Swiss 240’s and wondering if there is an advantage of straight pull spokes over J bend ?

FBinNY 

Yes ---------, and no.

The logic for straight pull spokes relates to steel's properties, specifically tensile strength.

The tensile yield strength in shear is roughly 80% of that in tension. So, as the J-bend spoke turns to enter a hub it loses 20% of it's strength. Following the logic that a chain is as strong as it's weakest link, this is the main reason for DB spokes, and also why the thin section usually has 80% of the cross section of the ends.

So the main argument against J-bend is removed when we use butted spokes, negating the need for straight pull.

There are also other considerations, but when all is said and done, neither is superior if the overall design and execution are done well.

BTW the main reason that J-bend has dominated for a century relates to hub manufacturing considerations. Hubs with flanges drilled from the sides are much simpler to produce than hubs designed for SP spokes.

masi61

I’m curious if custom wheels with straight pull spokes are harder to build (for an amateur wheelbuilder) compared with J-bend. My LBS wheelbuilder primarily builds with J-bend and he is quite conservative with regard to bringing up the spoke tension as he stress relieves the spokes in the build multiple time before doing the final truing. When I take the wheels he makes and start riding them I almost always have to take advantage of his complimentary tension and truing after riding them for 100 to say… 1,000miles. Once the final tensioning is done they tend to stay that way for a long time.

I have thought of trying to build a set of straight pull Dura Ace wheelset using used Dura Ace 7850 straight pull hubs. Seems like the spoke tension would need to be higher. I’d have to ask the wheelbuilder what he thinks, same with the spokes, maybe the ultra lite DT Swiss butted spokes would work for lower spokes count front hub (18 spokes) but as a 200 pounder , I’m reluctant to trust 24 spoke rear wheel. Maybe those who use straight pull hubs could speak to how strong of a wheel a 24 spoke rear would be for an ordinary 200 pound road rider.

Andrew R Stewart 

J bend spokes are slightly easier to build with IMO but not by much. J bend limit the spoke rotation (as opposed to wind up) during the tensioning/truing. J bends are more widely available in many gages. J bend hubs generally tolerate different spoke angles/crossings better than straight pull hubs do.

But as Francis said either spoke type can result in a well made wheel that lasts a long time. Andy (whose spoke are bent to the left)

FBinNY 

Yes, they're harder, but only slightly.

I hate straight pull because I prefer to load all spokes into the hub first, then lace one flange at a time.

J-bend spokes stay put, and I stabilize the second side with 2 rubber bands while lacing the first. Straight spokes don't stay put and become a pain. I rarely deal with spoke twist because I grease the threads, so no difference once they're laced.

As to weight-----

200#s is pushing it for a 24 spoke rear wheel. If asked, I'd turn it down unless I knew the rider well (riding style matters). Also, I would not increase tension because it would raise the dead load, leaving no room for the higher working load. Instead I'd use a deep section rim to increase radial rigidity.

But again; 200#s on a 24 spoke rear wheel is asking for trouble. Fine for the front, though.

Dan Burkhart 

I build a few hundred wheels per year and at least 80% are straight pull. I also do wheel repairs for three shops and individuals, and while the majority are broken elbows on J bend spokes, I do see straight pull with the heads broken off.
As to build difficulty, it depends on the hub design, Those that have the spoke pass through a hole are fairly easy, but those that slip into a pocket can be a but of a pain to keep in place as you bring them up to initial tension.
I designed and built a lacing jig that allows me to lace the wheel laying flat which helps a lot.
One thing that is definitely easier with straight pull is lacing pattern considerations. There is no questions about leading/trailing heads in or out, or choices in number of crosses because that is all dictated by the hub. It points the spoke where it needs to go.
One thing that is more difficult is measuring the dimensions for spoke length calculations. It is mostly straight forward but measuring the spoke offset can be a challenge.
Note that you need to check both sides for offset as some hubs will have more offset on one side to allow for using the same spoke length as the other.
Oh, one more thing about hub design. There are some straight pull hubs, usually ones that are radial lacing on one side, that have to have the axle and bearing removed to insert the radial spokes. (I am looking at you Tune and Spinergy) Wouldn't be so bad if they shipped the hub without the bearing installed but as it is, you risk ruining the bearing in a brand new hub just to get the thing laced. Dumb design in my opinion.

Dan Burkhart 

You might find that the Dura Ace spoke holes are too small to accommodate the heads of vendor straight pull spokes. They are made to be used with Shimano proprietary spokes.

masi61

Oh, that makes sense. I kind of got the impression that they needed extra beefy spokes. I wonder if you could build up a hub like that with some flat aero straight spokes if you could not source the OEM proprietary spokes.

SoSmellyAir

Oh dear. Just when I thought I got over the fear of my CF wheels assploding, you dragged me in again.

Shoot, my Mavic Ksyrium Elite wheelset only has 20 spokes in the rear, I better fast for a day or so.

FBinNY 

Don't diet. Read the rest of the post. Weight isn't the only factor, IMO it's not the most important factor either. As I've said here countless times, I've known gorillas that never have problems, and ballerinas that always do.

So, as I said in the post, I wouldn't build 20 spoke wheels for a stranger, but would for someone I knew.

Ryan_M

As a novice to wheel building it's good to here my (limited) experience matches those that know what they say. I've built a JB wheel set and a SP set. I found the JB easier to build, and more so to do the final truing. The SP has a bit of a coolness factor to it, I like the look of the machined hubs. TBH I'll probably go SP on my next build (based completely on cosmetics), even if the build is a bit more difficult it doesn't last that long.

bblair

Yes, there is an advantage: they look really cool.

urbanknight

As far as ride characteristics, I can’t tell the difference. As far as durability, any properly hand built wheel should last. I do avoid building round spokes in straight pull because I have no idea how to keep them from just spinning around (or even if that’s really an issue).

FBinNY 

There's no issue.

Head to hub friction is consistently much greater than thread friction.

However, there's a PIA factor in that you have to hold spokes while initially threading on nipples. No tools, just your other hand, but stays necessary until there's some tension, and friction takes over.

cpach

Straight pull spokes don't need the nipple heads set, which saves a (short, fairly easy) step. They look (arguably) cool. I think the advantages regarding spoke fatigue are probably mostly irrelevant for double butted spokes built with good technique, but may have slight advantages for mass production. They make it harder to find a spare spoke at a given random bike shop. Anecdotally flange failure seems pretty similar either way.

I don't have strong feelings about it, but I never choose straight pull hubs for myself nor really recommend them. If someone wants them, I'm happy to build it for them.

Bike Gremlin

J-bend spokes are easier to find, and when you get them in good quality, they last for years and years.

Relja KISS Novović

Pop N Wood

Straight pull spokes can be replaced without removing the rear cassette.

Not an issue in the shop but a very nice thing on a touring bike that may require spoke replacements on the trail.