[Closed] Advantages of Straight pull over J bend spokes

...not at all an expert in spokes and hubs. I buy my complete wheels.

But I would guess, only when talking about the spoke:

Same quality material, same spoke diameter:

you are able to put more tension onto the straight pull. It will hold up in fatigue better as well. And the whole design is stiffer.

Reason: metal is great for tension loads.
The "J" introduces bending peak loads.
Bending is a difficult load case for metal parts.
Lowers the possible tension you are able to put onto the spoke and makes the design "soft".

But others will know more / have an better explanation.
😉

Sounds plausible, but in practice I've broken spokes at plenty of spots other than the J-bend.

I thought the advantage of straight pull spokes was that they are more bling and signal the higher economic status of the rider.

I had an old set of Shimano hubs that were straight pull, and I think hope also used to do straight pull and my mate had a set. My only observation was it was a PITA to get spokes for either as they were an odd size.

I'm not sure the durability of J bend spokes is really an issue.

more bling and signal the higher economic status of the rider.

haha.
Totally agree.

But others will know more / have an better explanation.

more bling.
😉

j bend are easier to get when you break one and easier to tension.

you are able to put more tension onto the straight pull

Irrelevant, either type of spoke will pull through a rim (or pringle the wheel) before they snap from tension alone. Also, the straight pull spoke will spin and wind up more than a J-bend so often in practise are a pain in the arse to tension by comparison.

Also, a J-bend spoke is interfaces with the hub at the head AND at the elbow in the hole and bears against the flange, so it's not just the head taking load, where as pretty much all the tension load on a straight pull is on the head, and depending on the support at the flange you may still have a bending/point load as it leaves the flange. So swings and roundabouts there.

You're also locked into a single lacing pattern with SP, fine if you just buy wheels, not so fine if you build your own and might want to rebuild in some other configuration at some point.

They are generally a bit lighter and easier to replace spokes though, but how much that matters is related to how often you break spokes....

I'd take a 32 DB J-bend, easy to source spoked wheel over a 28 straight pull any day, but I build my own anyway and I'm not a habitual spoke breaker.

Easier to lace a straight pull. Less chance of getting the order of putting the spokes in wrong 🙂

Reason: metal is great for tension loads.
The "J" introduces bending peak loads.
Bending is a difficult load case for metal parts.

This is all I can think of.
Metal fatigue at the bend in the spoke.
I've only broken spokes through damage, and they didn't break at the bend.
Maybe if you used the same wheels daily for 20 years or so....

Also, the straight pull spoke will spin and wind up more than a J-bend so often in practise are a pain in the arse to tension by comparison.

But yeah, i'd not go out of my way to specifically buy SP over J-bend, unless the hub has some specific reason for SP, like a very lightweight model for instance.

Edit:- I have found however that SP wheels need far less bedding in and twanging during the build. J-Bends settle into the flange (and each other) as you increase the tension and need to be destressed more. Not sure what the exact terminology is...... but that twang twang thing you get when flexing the rim.

In theory doesn't have the weakness that J-bend supposedly does on the bend (but that rarely snaps on the bend anyway and has been a reliable design for a very long time).

Factory wheels can build up with fewer spokes with straight pulls and strong enough hub and rims. Not sure that gives any advantage though other than cheaper for them.

Disadvantage - getting hold of straight pull from an LBS that will fit your wheel design, and greater cost.

Whats all this about "availability".
I can get straight pulls in 48 hours in almost all lengths. (And multiple models/colours).
Only becomes an issue if you need it right now.

I have a set of older SP Pro2 hubs which originally came with crests, changed the rims to Chinese carbon about 5 years ago reusing the straight pull spokes and nipples and they're still going strong. They come with spare spokes so never had to worry about replacements.

Edit:- I have found however that SP wheels need far less bedding in and twanging during the build. J-Bends settle into the flange (and each other) as you increase the tension and need to be destressed more. Not sure what the exact terminology is...... but that twang twang thing you get when flexing the rim.

might be connected to this:

And the whole design is stiffer.

Others:

machining of the Hub.
Hub for J spokes needs simple machining only. Ideal, in the old times, for mass production.
SP Hub: more complex machining. But possible with modern machines.

Others:

No idea if this is connected to J or SP:
out of aerodynamic reasons spokes might be "flat" today. Means base material for the spoke might be not "wire" any more?
And the "J" was perfect for forming the end of an wire...
The idea here: IF you need a "FLAT" spoke - then it's easier, for the spoke machining - to manufacture a SP spoke...?
No idea.
Possible?

@amedias:
SP:

They are generally a bit lighter

But I'am not a spoke / rim / wheel expert.
Ordered one week ago a new wheelset with good old J spokes.
Out of one reason: cheaper!
😉

@deadkenny:

Factory wheels can build up with fewer spokes with straight pulls

good point as well.
That indeed is an indication that SP spokes are able to take more tension...

😉
Nice thread.
Good discussion!!!

ghostlymachine - Member

Whats all this about "availability".
I can get straight pulls in 48 hours in almost all lengths. (And multiple models/colours).
Only becomes an issue if you need it right now.

couldn't agree more. It's an non issue for the vast majority of us.

Also, the straight pull spoke will spin and wind up more than a J-bend so often in practise are a pain in the arse to tension by comparison.

Nah, i've got a pair of soft faced pliers for gripping near the nipple.

Yeah, so [i]by comparison[/i] it's an arse, cos you have to hold the spoke! J-bend only winds up a tiny bit and it's easier to do the 'feel the wind and back off' than it is with SP.

It's not stopped me building them when people ask, but It's not my preference.

isn't that an indication that - for same diameter - you would be able to put more tension onto a SP spoke?

Nope, because as said before, the tension is limited by the rim not the spoke. Even on super skinny 1.5mm or less spokes. The breaking force in tension for any spoke is well in excess of the load the rim could handle, If you're takin a wheel up to X newtons, it's X newtons whether it's in a thin spoke, fat spoke, J-bend or SP, it's still X.

ghostlymachine - Member

Whats all this about "availability".
I can get straight pulls in 48 hours in almost all lengths. (And multiple models/colours).
Only becomes an issue if you need it right now.

I(broke 3 spokes in the rear wheel of the tandem while touring the netherlands. Got to the nearest bike shop and they had the correct length spokes there and then. Thats a huge advantage in my eyes. a straight pull spoke wheel would have meant end of tour ( at least for a couple of days)

how do you know they didn't have spare spokes? And why didn't you have spares with you 😀

double post

@amedias:
thanks. Good point and good discussion.
But

The breaking force in tension for any spoke is well in excess of the load the rim could handle

This is very difficult to judge. Depending on the tension level you are able to put different levels of fatigue onto the spoke?
What you say: is it possible that you put the same tension onto a SP spoke and a J spoke - but that a SP spoke wheel needs less SP spokes because it takes more fatigue load?
Mayb same average tension (pre-tension) but higher allowed "changing loads" / fatigue?
Possible?

No idea if this makes sense.
Just try to find a good explanation for myself.
😉

howsyourdad1 - Member

how do you know they didn't have spare spokes? And why didn't you have spares with you

I haden't updated my spares kit since rebuilding the wheel with a differnt hub - rookie error.. Ihad the spkes for the front ( two differnt lengths) needed 3 of the same legth. This was a shop serving Dutch commuters. Only galvanised j bend spokes but a full range of them. NO stainless, no branded, no stright pull.

Yeah, so by comparison it's an arse, cos you have to hold the spoke!

I broke 3 spokes in the rear wheel of the tandem while touring the netherlands. Got to the nearest bike shop and they had the correct length spokes there and then. Thats a huge advantage in my eyes. a straight pull spoke wheel would have meant end of tour ( at least for a couple of days)

Oh, and FWIW, some straight pull hubs you can get the wrong end of the spoke threaded and use a nipple as a temporary head as a get you home bodge. Obviously need someone with spoke threader!

my experience of spoke breakages are that they either break at the nipple end at the start of the thread (obviously due to the thread cutting process) or an inch or so up from the J - so as a result of the J. For a metal cylindrical homogeneous bar the point of fracture under tension should be at the centre, but a J-spoke isn't homogenius due to the thread and J, so it is not surprising that seems either the thread end or J-end are the weaker points due to their manufacturing processes that create those features - then it is a straight fight as to which is the weakest point.

One advantage of straight pull is that spokes are easier to replace - I've had to remove cassettes in the past to replace J-pull spokes which I wouldn't have had to do in the case of straight pull. Also the chances of breaking a spoke are reduced. A mate of mine rode into a tree stump once and pringled his wheel. Amazingly all the spokes were fine - they just popped out of the location feature at the hub end as the tension was removed due to the impact with the tree. Unfortunately the rim was trashed, but the spokes could have been used again. With J-pull the spokes would have buckled and bent under the compressive load.

I just prefer straight pull. A far more elegant design. Not necessarily better in the real world, but on paper much nicer.

Obviously need someone with spoke threader!

Ghostly - a evil stick jumped into the wheel and ate the spokes. Just one of those things

Doesn't everyone carry a spoke threaderwith them?

Not these days 😀
Used to be standard in almost every shop i went in back in the 80s and 90s.

Most people just look at you blankly now.

This is very difficult to judge

It's not, it's very easy to measure, you simply apply load until spoke snaps 🙂

The key bit is that the tension a spoke can handle is way way below the tensions at which the rim will start to fail, either by pulling a nipple though or pringle due to buckling, so even if a SP spoke could handle theoretically higher tension, it's irrelevant in practise as the spokes aren't anywhere near that limit.

The fatigue side of things is more complex, I'll grant you that, and there is some sway to the argument that a SP spoke is going to suffer less fatigue at the hub interface end, but even that is not simple and most spoke fatigue failures are a result of excessive overloading and repeated cycles, ie: a wheel that wasn't built sufficiently for it's intended use. The rim also has a big part to play in spoke loadings and how they are distributed as well as how many spokes there actually are etc.

Fewer spokes at higher tension does not necessarily a better wheel build. I'm very much of the opinion that the weight saving of fewer spokes is simply not worth it in practise. It's a marginal reduction in weight, and increases both the fatigue and the overall strength of the wheel. A properly built wheel, with rims, hubs and spokes chosen for the applicable loads and intended use is a winner everytime, regardless of minutiae of exactly what those components are.

There is a lot of good literature out there on wheels, Jobst's book is worth a read if you haven't already read it.

Doesn't everyone carry a spoke threaderwith them

I would imagine a dutch bike shop serving only commuters might have one 😀

no you are right, for tourers etc j bend for sure, but in general , availability isn't an issue

@amedias:

The fatigue side of things is more complex, I'll grant you that, and there is some sway to the argument that a SP spoke is going to suffer less fatigue at the hub interface end, but even that is not simple and most spoke fatigue failures are a result of excessive overloading and repeated cycles, ie: a wheel that wasn't built sufficiently for it's intended use. The rim also has a big part to play in spoke loadings and how they are distributed as well as how many spokes there actually are etc.

I'm very much of the opinion that the weight saving of fewer spokes is simply not worth it in practise. It's a marginal reduction in weight, and increases both the fatigue and the overall strength of the wheel.

[url= https://www.amazon.com/Bicycle-Wheel-3rd-Jobst-Brandt/dp/0960723668 ]Jobst Brandt - The Bicycle Wheel[/url]

^ seriously, worth a read if this stuff interests you.

there are others too, but Jobst has some nice techy stuff in it 🙂

[url= https://www.wheelpro.co.uk/wheelbuilding/book.php ]Wheelpro/Musson book[/url]

It's a bit off sharing pirated material on here.

I've never snapped a spoke at the bend. I build my own wheel so would never use straight pull.

It's a bit off sharing pirated material on here.

You're right, I've now missed the edit window so I've emailed the mods now to ask them to remove it

Mods - please could you remove the link I posted.

obviously due to the thread cutting process

I'm pretty sure spoke threads are rolled rather than cut to reduce stress at that point.