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Old 03-10-09, 09:57 PM   #1
lukasz
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DT Revolution spokes... 2.0/1.5 or 1.8/1.5?

I've gotten the impression from doing some research that the 1.8/1.5 spoke is actually stronger (more reliable is a better choice of words maybe) due to the less pronounced difference in thickness (torque transmitted from the thicker part to the thinner part during tensioning). Is this purely theoretical, or generally accepted as fact?

I'm planning on lacing up a 32h 3x front wheel with these. Not normally a sucker for weight but hey, it is just a front wheel.
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Old 03-10-09, 10:11 PM   #2
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Not that I know of. 2.0 holds up better at the j-hook than 1.8, you also get a larger threaded interface.
I have yet to see a spoke break at the butt(that was not damaged by an outside source), I have seen lots(hundreds) of spokes break at the j-hook.
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Old 03-10-09, 10:42 PM   #3
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Yeah, I don't see your logic. 2.0/1.5/2.0 is stronger for a number of reasons: 1, more material against the hub holes. 2, the spoke is thicker at the part where it would normally break. 3, more spoke/nipple interface material. Now that I have more understanding of wheels, I would never use 1.8 spokes unless the hub was drilled specifically for them.
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Old 03-11-09, 12:27 AM   #4
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It's significantly harder to build a wheel with 2.0/1.5/2.0 without overtwisting the spokes is the thing. Probably a good idea to mark all the sides of the spokes with sharpie so you can see if they're twisting. I hear a rigid truing stand can help as well, so you can side load the wheel to detension each spoke while you turn its nipple.
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Old 03-11-09, 01:56 AM   #5
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Remember there's a difference between wheel-strength and spoke durability. If you build two wheels using 2.0/1.5 and another with 1.8/1.5 spokes, both tensioned to the exact same tension, then wheel-strength will be exactly the same. That is... they'll resist going out of true on bumps and impacts exactly the same. Both of them will be better than 2.0 straight-gauge spokes at keeping a wheel true.

HOWEVER, they both will have the same life-span as the 2.0 straight-gauge spoke. That is, the time til the spokes wear out from fatigue and start snapping at the bend will be about the same.

Personally, I like the triple-butted spokes with thickest end at the J-bend.

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Old 03-11-09, 08:00 AM   #6
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HOWEVER, they both will have the same life-span as the 2.0 straight-gauge spoke. That is, the time til the spokes wear out from fatigue and start snapping at the bend will be about the same.
I've read (but never seen confirmed) that butted spokes are actually more durable than straight gauge spokes since the thinner center elongates more under impact and reduces the load on the J-bend and spoke threads.
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Old 03-11-09, 08:50 AM   #7
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I've talked to several wheelbuilders and some of them told me the straight gauge 2.0 spokes are stronger and others told me that a double butted spoke is stronger because it flexes in the middle and because of this there's less breakage.
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Old 03-11-09, 08:54 AM   #8
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I read this in an old posting by Jobst Brandt. He's a bit of a... uh... traditionalist.

I'd just use some 1.8/1.6 but with 32 spokes on a front wheel that seems like overkill considering this will be going on a road bike and I weight 170 or so.


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It's significantly harder to build a wheel with 2.0/1.5/2.0 without overtwisting the spokes is the thing. Probably a good idea to mark all the sides of the spokes with sharpie so you can see if they're twisting. I hear a rigid truing stand can help as well, so you can side load the wheel to detension each spoke while you turn its nipple.
This is kind of what I'm getting at. Brandt seemed to say that the discrepancy in size makes for spokes that twist much more when tensioning.

Has anyone had experience with both 2.0/1.5 and 1.8/1.5? Which are easier to build with? I don't want to go triple-butted because of price.

edit: eek, just realized I'd probably need washers to make 1.8/1.5 spokes work. I'd rather deal with the 2.0/1.5 windup than add another part to my wheel.

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Old 03-11-09, 11:37 AM   #9
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Use the 15-16 for the front or rear. Double butted spokes are more durable because they take the stress off of the stress risers in the spoke (the threads and the bend).
Straight guage spokes are only easier to build with because they don't wind up as you tension them. They are also cheaper.
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Old 03-11-09, 01:26 PM   #10
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I'm likely going to use 2.0/1.5 (14/16?) because I don't want to use washers on my hub.
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Old 03-11-09, 03:16 PM   #11
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It's because the 2.0 section exerts more torsional force on the 1.5 section during the trueing process. A 1.8/1.5 will be easier to build, because you'll have less torque twisting up the middle of the spoke.

Straight guage are individually stronger, but the distribute stress poorly, so as an aggregate whole make for a slightly more failure prone wheel.
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Old 03-11-09, 03:28 PM   #12
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I have two sets of wheels that I built with Revolution spokes, 2.0-1.5-2.0. I hold each spoke with pliers when reaching higher tensions to avoid windup. Lubricating the threads will help, I use spokeprep as a lubricant and to help stabilize tension. In the future I will use 2.0-1.8-2.0 spokes on the driveside rear. Revolutions stretch. under high tension.

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Old 03-11-09, 07:01 PM   #13
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Standard DT DB - 2.02mm - 1.77mm.
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Old 03-11-09, 09:47 PM   #14
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"because they take the stress off of the stress risers in the spoke (the threads and the bend)." QUOTE.


Spoke threading is by "rolling", rather than "cutting",

hence,

few if any "stress risers", on the thread.


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Old 03-12-09, 10:50 AM   #15
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Spoke threading is by "rolling", rather than "cutting", hence, few if any "stress risers", on the thread.
Rolling spoke threads doesn't produce the sharp V at the thread root like cutting threads does but there is still a small radius curve so it is a stress raiser to an extent. Spokes do break from fatigue at the threads, just not as often as at the J-bend.
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Old 03-16-09, 08:14 AM   #16
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I would build with the largest spoke size at the hub end as it will have less movement, less twisting, it will fit tighter. Smaller spoke head ends will twist and cause elongation in the hub hole increasing the twisting.
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Old 03-16-09, 11:45 AM   #17
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This is kind of what I'm getting at. Brandt seemed to say that the discrepancy in size makes for spokes that twist much more when tensioning.
I don't see how that would be (and I'm not sure Brandt was inferring it, either). How thick the spoke is will determine how easy it is to twist, irregardless of how thick other parts of it are, as long as the thin part is the same length.
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Old 03-16-09, 01:10 PM   #18
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Originally Posted by DannoXYZ View Post
Remember there's a difference between wheel-strength and spoke durability. If you build two wheels using 2.0/1.5 and another with 1.8/1.5 spokes, both tensioned to the exact same tension, then wheel-strength will be exactly the same. That is... they'll resist going out of true on bumps and impacts exactly the same. Both of them will be better than 2.0 straight-gauge spokes at keeping a wheel true.

HOWEVER, they both will have the same life-span as the 2.0 straight-gauge spoke. That is, the time til the spokes wear out from fatigue and start snapping at the bend will be about the same.

Personally, I like the triple-butted spokes with thickest end at the J-bend.
A properly build wheel's spokes won't wear out.

According to Brandt, the butted spoke reduces fatiguing stress at the bend, so wheel and spoke durability will be superior with the butted spoke.

I haven't done side-by-side durability tests comparing straight and butted spokes, but I have built dozens or perhaps hundreds of wheels with butted spokes, and they are certainly no worse. I tend to believe Brandt. His assertions are always backed up with data that he collects. He never uses mere theory.
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Old 03-16-09, 03:07 PM   #19
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A properly build wheel's spokes won't wear out.

According to Brandt, the butted spoke reduces fatiguing stress at the bend, so wheel and spoke durability will be superior with the butted spoke.

I haven't done side-by-side durability tests comparing straight and butted spokes, but I have built dozens or perhaps hundreds of wheels with butted spokes, and they are certainly no worse. I tend to believe Brandt. His assertions are always backed up with data that he collects. He never uses mere theory.

Actually, spokes do wear out. A properly built wheel only prolonges the inevidable, so much so that usually the rims go bad first. I am a Jobst Brandt loyalist myself. And it was my impression that butted spokes are less prone to going slack for a given rim deflection, which results in increased durability.

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Old 03-16-09, 03:33 PM   #20
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Ask Jobst or google his posts. He says he's been reusing the same spokes over and over indefinitely. He rides a lot, and hard.

I've built many wheels, many for myself, and the only spokes I've broken were on crappy wheels, improperly built. That was long, long ago.

Of course, you might break spokes on a bike with too few spokes for the job. I notice the latest trend is for very few spokes. Seems pretty foolish to me.
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Old 03-16-09, 03:43 PM   #21
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Ask Jobst or google his posts. He says he's been reusing the same spokes over and over indefinitely. He rides a lot, and hard.

I've built many wheels, many for myself, and the only spokes I've broken were on crappy wheels, improperly built. That was long, long ago.

Of course, you might break spokes on a bike with too few spokes for the job. I notice the latest trend is for very few spokes. Seems pretty foolish to me.

The last paragraph from the link below. They will fail at some point.

"The reason you can reuse spokes is that their failure mode is fatigue. There is no other way of causing a fatigue failure than to ride many thousand miles (if your wheel is properly built). A crash does not induce fatigue nor does it even raise tension in spokes unless you get a pedal between them. Unless a spoke has a kink that cannot be straightened by hand, they can all be reused."

http://www.sheldonbrown.com/brandt/reusing-spokes.html
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Old 03-16-09, 04:53 PM   #22
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OK, spokes wear out. I don't deny that. But many thousand miles? Most bikes never reach ONE thousand miles! Spoke breakage should be extremely rare. If it happens to you, don't attribute it to normal wear.
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