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Old 09-17-11, 08:20 PM   #1
yellowdog76
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Spokes: double butted or straight gague

Any preference? Are DB that much better?
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Old 09-17-11, 10:02 PM   #2
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Lighter and more aero so of course you want them. But the real advantage is supposed to be that the thinner section is more elastic and absorbs stress that would otherwise pull on the elbow and eventually break it.
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Old 09-17-11, 10:59 PM   #3
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The original theory behind butted spokes was premised on the concept that a chain is as strong as it's weakest link. In a plain gauge spoke the elbow has about 80% of the strength of the rest of the spoke. Likewise the reduced diameter at the threads reduces strength. So 20% of the material throughout the length of the spoke is excess baggage.

In practice they deliver far more than the original expectations. A well selected butted spoke will outlast a plain gauge spoke of the same gauge (at the ends) significantly. It isn't often that less is actually more, butted spokes are one of the rare cases where it true.
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Old 09-18-11, 02:26 AM   #4
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Are DB that much better?
better for what?

What are your needs?

add: how many do you plan to have in your wheel?

Last edited by fietsbob; 09-20-11 at 10:57 AM.
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Old 09-19-11, 08:13 AM   #5
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Originally Posted by fietsbob View Post
better for what?

What are your needs?
My needs are a tough wheel that can handle training rides with a bit of gravel thrown in there. My LBS sort of looked at me funny when I said I wanted a 650b wheel built up with DB spokes. I had read the same, that the thinner section deals with the road stress better....
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Old 09-19-11, 10:13 AM   #6
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Originally Posted by FBinNY View Post
The original theory behind butted spokes was premised on the concept that a chain is as strong as it's weakest link. In a plain gauge spoke the elbow has about 80% of the strength of the rest of the spoke. Likewise the reduced diameter at the threads reduces strength. So 20% of the material throughout the length of the spoke is excess baggage.

In practice they deliver far more than the original expectations. A well selected butted spoke will outlast a plain gauge spoke of the same gauge (at the ends) significantly. It isn't often that less is actually more, butted spokes are one of the rare cases where it true.
All of this is spot on. The other side of this is that straight gauge spokes
are more readily available in far off parts and places, slightly easier to build with,
and are capable of making a relatively durable wheelset when properly tensioned.

For what you are describing, I would not hesitate to use straight 14 gauge
stainless spokes from Wheelsmith or DT Swiss. Possibly your bike shop
has a limited supply of spokes and they might even be one that cuts and
threads a universal long spoke to each job........this cuts down on the inventory
they have to carry..........but in the final analysis, DB spokes build a more
durable wheel without question.
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Old 09-19-11, 10:36 AM   #7
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Originally Posted by yellowdog76 View Post
My needs are a tough wheel that can handle training rides with a bit of gravel thrown in there. ....
But tough isn't exactly a specified entity. There are basically two flavors: durability and strength. A wheel with butted spokes will be more resistant to fatigue, but less resistant to tacoing.
But training rides, assuming you're not a clydesdale, butted spokes would be a better choice.

Now, whether you'd notice the improvement or not is another question entirely. Better-than-required isn't a feature you're likely to notice much.

But placebo is a powerful thing, quite a few people will testify to getting a better ride out of a bike as long as they know it's better.
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Old 09-19-11, 01:14 PM   #8
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Originally Posted by yellowdog76 View Post
Any preference? Are DB that much better?
Butted.

They stretch more for a given strain so the wheel can tolerate bigger hits before the wheel becomes laterally unsupported, shifts sideways, and collapses as the rim returns to its original shape.

They make for a wheel that's more tolerant of building errors stress relieving and correcting spoke lines since stress is more concentrated in the thin section which does not have residual stresses from the head forming operation or a bend at the nipple (due to deep rims with small hub flanges).

At around $0.10 a spoke for parts that last indefinitely (through many rim and bearing replacements) it's cheap insurance.
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Old 09-19-11, 01:21 PM   #9
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But tough isn't exactly a specified entity. There are basically two flavors: durability and strength. A wheel with butted spokes will be more resistant to fatigue, but less resistant to tacoing.
No.

A wheel tacos when there's a hard enough impact to slacken the spokes, the rim moves off center, and the wheel collapses as the rim returns to its original shape and applies tension to the spokes in that off-center position.

The amount of force it takes before the rim becomes laterally unsupported due to slack spokes is dependent on spoke tension and how much is lost as the rim bends towards the hub.

With the rim's elastic limit or spoke bed fatigue strength the limits on spoke tension you can get butted spokes just as tight (I got 120kgf drive side on my last rear wheel built with 2.0/1.5 spokes and 110kgf on my last front) so that's the same.

The thinner center section of butted spokes stretches more at a given tension so they require a bigger rim deflection before they go slack and thus make a wheel less likely to taco.

Thinner straight gauge spokes would do the same but the big machine-lacing friendly holes in the hubs can leave parts of the elbow in an unsupported position where they can't be stress relieved which leads to repeated fatigue failures until you give up and rebuild the wheel with thicker spoke elbows. They'll also survive fewer fatigue cycles which is especially important when you don't properly stress relieve and correct spoke lines (as on many machine built wheels).

Straight gauge spokes are often recommended to beginning wheel builders because they windup less although with proper lubrication (I like anti-seize) this is manageable and a tape flag on representative spokes (first after the valve hole, for both sides in a rear wheel) will let you know how much to correct even if you lack the experience to feel it (equal torque on the spoke wrench indicates no windup). I built my first wheels with 2.0/1.5 spokes front and non-drive side and didn't need to true them until I replaced the rims (12-14 years for the front).

Quote:
But training rides, assuming you're not a clydesdale, butted spokes would be a better choice.
Butted spokes are an especially good idea if you're a Clydestale because you put more weight on your wheels (so they're more likely to fold) and have a higher magnitude to the stress variation leading to reduced fatigue life.

Last edited by Drew Eckhardt; 09-20-11 at 09:59 AM.
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Old 09-19-11, 01:31 PM   #10
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anybody got a good source for spokes (either single or double butted)? Not looking quite yet as I'm waiting for my hubs to come in to make some final measurements, but I'm just trying to stock up my knowledge base of where I should be looking.
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Old 09-19-11, 01:46 PM   #11
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anybody got a good source for spokes (either single or double butted)? Not looking quite yet as I'm waiting for my hubs to come in to make some final measurements, but I'm just trying to stock up my knowledge base of where I should be looking.
I like to buy from http://www.universalcycles.com/ They sell individually as well so you can buy in whatever quantity you like.

I will give a +1 on the DB for the reasons given above. I am a Clyde and run DB spokes on my MTB wheels. These wheels take a lot of punishment and have been rock solid. The only issue I have had involved crash damage so I can't blame the spoke choice there. On a positive note, I was able to straighten the rim in the field enough to finish the last five miles of the race and the spokes did hold the wheel together long enough to finish.
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Old 09-20-11, 09:54 AM   #12
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+1 for doble butted spokes- I preferDT swiss Competition
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Old 09-20-11, 10:01 AM   #13
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DT Swiss are well made too but changed the design of thier elbow a few years back to make machine building faster and less expensive. This resulted in a slightly larger radius at the bend. For this reason, I more often go for the Wheelsmith brand.
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Old 09-20-11, 10:51 AM   #14
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No..
To each his own then.
I'd say that a thicker spoke makes for a laterally more rigid wheel, and that a laterally more rigid wheel is more resistant to tacoing.
Maybe you're thinking of a special subset of tacoing due to a fairly pure vertical load, where I'm thinking of a significant lateral component.
In the case of a lateral component, one side of spokes has to stretch for the other side to go slack, and a thicker spoke will stretch less for the same force.
All other things being equal, in terms of lateral rigidity, available cross section is hugely important. Reducing this by the use of butted spokes or by reducing the spoke count leads to the same result - more sideways displacement for the same amount of force.
If you're a clyde, eventually there's a tradeoff. What use is good durability if the wheel flops too much sideways when honking for instance?
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Old 09-20-11, 10:57 AM   #15
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how many in the wheel?

I Have a 36 spoke wheelset, built with straight 15 gage spokes ..
its been fine for decades, but its a sport bike, not a commuter..

Last edited by fietsbob; 09-20-11 at 11:02 AM.
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Old 09-20-11, 11:00 AM   #16
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I'd say that a thicker spoke makes for a laterally more rigid wheel, and that a laterally more rigid wheel is more resistant to tacoing.
Maybe you're thinking of a special subset of tacoing due to a fairly pure vertical load, where I'm thinking of a significant lateral component.
You're right, that more material increases rigidity, and this would increase the force required to flex the wheel past the point of no return and taco it (or Potato Chip, which is a better description, and what we used to call it before food fashions changed).

But this isn't how wheels normally fail (or shouldn't be) so I design to improve fatigue life, and ride properties. I only use plain gauge spokes for track wheels, and then mostly for sprinters, or for small tracks where lateral strength is more of a priority than fatigue life. On road wheels, I'll sometimes use plain 14g form the right and butted 14g for the left to suit a specific purpose, like the Mt. Washington hill climb.
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Old 09-20-11, 11:01 AM   #17
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At around $0.10
decimal point or time line [1940?] is way off
plain, straight gage, retail is $1.00 each .
DB are at least double that.
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Old 09-20-11, 11:07 AM   #18
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yellowdog76, The quality of the wheel build over scores which style of spoke is used. That said, I think that 15-14 DB spokes adds a little bit extra to the wheel's durability.

Brad

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Old 09-21-11, 12:03 AM   #19
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You're right, that more material increases rigidity, and this would increase the force required to flex the wheel past the point of no return and taco it...But this isn't how wheels normally fail (or shouldn't be)
It's fairly frequent for light MTB XC race wheels, at least in "my" crowd. Then you either up the spoke count or the spoke dimension for the next pair of race wheels. I've got a chart somewhere showing how count vs gauge compares, which wasn't exactly how I'd imagined.
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Old 09-21-11, 01:00 AM   #20
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My needs are a tough wheel that can handle training rides with a bit of gravel thrown in there...I wanted a 650b wheel built up with DB spokes...
Oh good, I get an excuse to show my tough 650B wheel build with DB spokes.


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Originally Posted by himespau View Post
anybody got a good source for spokes (either single or double butted)?...
http://www.danscomp.com/products-PAR...ted_Spoke.html Very good spokes BTW. For whatever it's worth, DT Swiss Comp spokes required washers on the same hub the Sapim Race spokes fit snug enough not to need them.
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