Another day with wheels (you know the drill).
Today I rebuilt a wheel that had slack spoke tension.
Before rebuild
Nice save there
I've been doing a lot of rebuilds from this particular shop lately.
Obviously I can't say which one.
The spokes before rebuild were DT Revolution spokes.
A "lightweight to hold" wheel has an obvious appeal point—the scale shows a smaller number.
On the other hand, things like "good engagement" or "the wheel accelerates when you push" are hard to quantify.
If "lightweight to hold" is all that matters, Revolution spokes are the best choice,
but these spokes are picky about which rim and build method you use.
I'll write about this another time, but when you build with Revolution spokes,
most modern rims will exhibit plastic deformation
in the spoke's elongation direction.
I put marker tape at the intersection points of the spoke lacing pattern to check the tension.
As you can see, the tension is way too slack.
More tension isn't always better, but this is just too loose.
And with good reason—if you tensioned it any higher on an Open Pro,
the spokes would start elongating, so it's built in a range where that doesn't happen.
I don't see the point of using Revolution spokes just for that.
Sure, it would be heavier by a few dozen grams, but building a Competition spoke wheel properly
would likely result in a better wheel overall.
(Though, admittedly, "heavier" doesn't have much persuasive power with the average person)
The customer came to us with the requirement "Can you make it tighter?"
so they probably didn't ask for Revolution spokes in the first place.
In the end, it's just the builder's self-satisfaction.
Just wanting to build a lightweight wheel to hold.
Since it's built around Revolution spokes,
the rider's weight and intended use weren't considered at all.
This is the front wheel, but the rear wheel is even worse.
(I'm out of time today, so I'll rebuild that tomorrow or later)
Spoke selection and build method were left to my discretion, so I spent a lot of time thinking about it.
I built it with Sapim CX-RAY anti-flat radial lacing,
and there are various other build methods that would've been better than the original build.
The 15mm wide Vittoria rim tape doesn't work with the Open Pro.
Even if you center it perfectly, it'll shift over time.
When I removed the tire, it was in this state—we were right on the edge of pinch flats.
That was close!
So I switched it to 18mm width tape.
Update: I felt like I shouldn't put this off,
so here's the write-up on DT Revolution spokes.
When you bend a wire (spoke), as long as the bend isn't too severe, it returns to its original state.
This deformation is called elastic deformation.
If you bend it harder, the deformation stays—it doesn't return to its original shape.
This permanent deformation is called plastic deformation.
It happens in the spoke's elongation direction, so it's not visually obvious,
but when you over-tension a spoke, plastic elongation occurs.
Or imagine soft mochi candy.
Once you've stretched it out, the mochi doesn't shrink back to its original length.
Here are the dimensions of three representative DT round spoke models (in mm).
Revolution achieves its lightness not just from the thin butted section,
but also because the butted section makes up a longer proportion of the total spoke length.
If we set a 2.0mm plain Champion spoke at 100%,
here's the relative density for the same spoke length (per our testing).
I've written this many times before, but
the relative density changes dramatically depending on spoke length—50mm versus 1000mm, for example.
A 50mm Revolution has almost no 1.5mm section,
while a 1000mm Revolution is almost entirely the 1.5mm section.
But actual 700C wheel spokes are in the range of 240mm to 306mm.
In that range, the difference isn't enough to matter.
Here's how Sapim CX and CX-RAY compare.
Different manufacturers, but since the relative density is nearly identical,
you can think of CX as Champion flattened by pressing,
and CX-RAY as Revolution flattened by pressing.
As a side note, among complete wheels with straight spokes from Sapim,
there are custom aero spokes with a Competition-equivalent density.
I wish they'd make those in butted form too...
But anyway, when I say "flattened by pressing," that's not a metaphor—
CX and CX-RAY are actually manufactured through press forming.
CX-RAY has higher tensile strength than other Sapim models,
and magnets stick to it more strongly.
The difference in how easily magnets stick isn't a material difference, but rather
the magnetic properties change during work hardening.
Speaking of work hardening,
"Higher tensile strength" looks like the diagram above.
CX-RAY breaks at a higher spoke tension than other spokes.
When work hardening makes something harder, it's also moving in the direction of becoming more brittle.
With Revolution spokes, as you increase tension,
that "stretching-like" behavior I mentioned happens.
If you keep turning the nipple while it's stretching,
the spoke keeps pulling out further and further from the nipple.
In extreme cases it can stretch several millimeters.
If you exhaust the spoke's threaded section inside the nipple before breaking,
it won't snap, but it can elongate that much.
CX-RAY, on the other hand, has a high breaking limit but is more brittle,
so as you increase tension, it barely stretches
and just cleanly "snaps" instead.
It typically breaks near the junction between the round and aero sections on the nipple end.
In the diagram above I drew the stretching zone with some width,
but in reality it's almost nonexistent.
Imagine the hub is the floor and the rim is the ceiling,
with a spoke hooked to the floor and connected to the ceiling nipple.
When you tighten the nipple, the spoke length decreases,
but with a stiff rim, the ceiling acts like a completely rigid body, so the rim doesn't flex.
With a softer rim, it can't withstand the spoke tension
and flexes downward toward the floor.
This is my theory, but I think softer rims (a flexing ceiling) share the spoke tension
between the spoke and the rim, whereas
stiff rims (a rigid ceiling) make the spoke bear all the tension.
What I'm getting at is that using Revolution spokes on a stiff rim
might cause that stretching effect more easily than on a softer rim.
From my experience, this seems to be true.
As for what constitutes a "soft rim" here, there's no clear line,
but something like a Mavic GEL280 lightweight tube rim would qualify.
I think you could build that wheel well before the Revolution stretching effect becomes a problem.
↑That's the idea.
Most modern aluminum rims, including the Open Pro,
fall into the "stiff" category, and for those rims,
you'd run into the Revolution "stretching zone" before you could finish building the wheel.
The front wheel at the start had low spoke tension probably to stay below the stretching zone.
But nowadays, with CX-RAY having nearly the same relative density as Revolution
and almost no stretching effect across the normal hand-building range,
I don't understand why anyone would insist on using Revolution.
On another note, I was asked indirectly by a colleague recently:
"I tried building an Ambrosio Formula Crono 20 with Revolution spokes,
and the spokes just kept stretching—I couldn't finish the build."
The person in the middle helps me a lot, so I had to explain things candidly, including trade secrets.
The Crono 20 is lightweight but counts as a "stiff rim".
The amount of rim flex during break-in relative to its weight is remarkably minimal.
If they'd accept just "this rim and spoke combination aren't compatible"
without further explanation, they'd probably solve it themselves anyway.
So that's why I don't use Revolution spokes.
If there were a work-hardened spoke with Competition-equivalent density,
I might use that instead, but Competition so rarely exhibits stretching
that there's not really a problem. When it does happen (→here)
I've written much the same thing.
In that old post I listed Revolution's relative density as 64.2%,
while this article says 63.5%—different numbers. That's because
I measure relative density repeatedly, so it changes sometimes.
Below 70% of a 2.0mm plain spoke seems to be the line,
and below that, unwork-hardened spokes (like Sapim Laser) are prone to stretching,
so I basically don't use them.
Saying "prone to" makes it sound probabilistic, like
"sometimes it doesn't happen."
That's not it. Once you cross a certain threshold, it happens 100% of the time—
the threshold is just lower. That's what I mean by "prone to."
I adopt CX-RAY not for its aero performance.
Except for costing the customer more money (it's expensive!),
I don't see any way CX-RAY is inferior to Revolution.
Today I rebuilt a wheel that had slack spoke tension.
Before rebuild
Nice save there
I've been doing a lot of rebuilds from this particular shop lately.
Obviously I can't say which one.
The spokes before rebuild were DT Revolution spokes.
A "lightweight to hold" wheel has an obvious appeal point—the scale shows a smaller number.
On the other hand, things like "good engagement" or "the wheel accelerates when you push" are hard to quantify.
If "lightweight to hold" is all that matters, Revolution spokes are the best choice,
but these spokes are picky about which rim and build method you use.
I'll write about this another time, but when you build with Revolution spokes,
most modern rims will exhibit plastic deformation
in the spoke's elongation direction.
I put marker tape at the intersection points of the spoke lacing pattern to check the tension.
As you can see, the tension is way too slack.
More tension isn't always better, but this is just too loose.
And with good reason—if you tensioned it any higher on an Open Pro,
the spokes would start elongating, so it's built in a range where that doesn't happen.
I don't see the point of using Revolution spokes just for that.
Sure, it would be heavier by a few dozen grams, but building a Competition spoke wheel properly
would likely result in a better wheel overall.
(Though, admittedly, "heavier" doesn't have much persuasive power with the average person)
The customer came to us with the requirement "Can you make it tighter?"
so they probably didn't ask for Revolution spokes in the first place.
In the end, it's just the builder's self-satisfaction.
Just wanting to build a lightweight wheel to hold.
Since it's built around Revolution spokes,
the rider's weight and intended use weren't considered at all.
This is the front wheel, but the rear wheel is even worse.
(I'm out of time today, so I'll rebuild that tomorrow or later)
Spoke selection and build method were left to my discretion, so I spent a lot of time thinking about it.
I built it with Sapim CX-RAY anti-flat radial lacing,
and there are various other build methods that would've been better than the original build.
The 15mm wide Vittoria rim tape doesn't work with the Open Pro.
Even if you center it perfectly, it'll shift over time.
When I removed the tire, it was in this state—we were right on the edge of pinch flats.
That was close!
So I switched it to 18mm width tape.
Update: I felt like I shouldn't put this off,
so here's the write-up on DT Revolution spokes.
When you bend a wire (spoke), as long as the bend isn't too severe, it returns to its original state.
This deformation is called elastic deformation.
If you bend it harder, the deformation stays—it doesn't return to its original shape.
This permanent deformation is called plastic deformation.
It happens in the spoke's elongation direction, so it's not visually obvious,
but when you over-tension a spoke, plastic elongation occurs.
Or imagine soft mochi candy.
Once you've stretched it out, the mochi doesn't shrink back to its original length.
Here are the dimensions of three representative DT round spoke models (in mm).
Revolution achieves its lightness not just from the thin butted section,
but also because the butted section makes up a longer proportion of the total spoke length.
If we set a 2.0mm plain Champion spoke at 100%,
here's the relative density for the same spoke length (per our testing).
I've written this many times before, but
the relative density changes dramatically depending on spoke length—50mm versus 1000mm, for example.
A 50mm Revolution has almost no 1.5mm section,
while a 1000mm Revolution is almost entirely the 1.5mm section.
But actual 700C wheel spokes are in the range of 240mm to 306mm.
In that range, the difference isn't enough to matter.
Here's how Sapim CX and CX-RAY compare.
Different manufacturers, but since the relative density is nearly identical,
you can think of CX as Champion flattened by pressing,
and CX-RAY as Revolution flattened by pressing.
As a side note, among complete wheels with straight spokes from Sapim,
there are custom aero spokes with a Competition-equivalent density.
I wish they'd make those in butted form too...
But anyway, when I say "flattened by pressing," that's not a metaphor—
CX and CX-RAY are actually manufactured through press forming.
CX-RAY has higher tensile strength than other Sapim models,
and magnets stick to it more strongly.
The difference in how easily magnets stick isn't a material difference, but rather
the magnetic properties change during work hardening.
Speaking of work hardening,
"Higher tensile strength" looks like the diagram above.
CX-RAY breaks at a higher spoke tension than other spokes.
When work hardening makes something harder, it's also moving in the direction of becoming more brittle.
With Revolution spokes, as you increase tension,
that "stretching-like" behavior I mentioned happens.
If you keep turning the nipple while it's stretching,
the spoke keeps pulling out further and further from the nipple.
In extreme cases it can stretch several millimeters.
If you exhaust the spoke's threaded section inside the nipple before breaking,
it won't snap, but it can elongate that much.
CX-RAY, on the other hand, has a high breaking limit but is more brittle,
so as you increase tension, it barely stretches
and just cleanly "snaps" instead.
It typically breaks near the junction between the round and aero sections on the nipple end.
In the diagram above I drew the stretching zone with some width,
but in reality it's almost nonexistent.
Imagine the hub is the floor and the rim is the ceiling,
with a spoke hooked to the floor and connected to the ceiling nipple.
When you tighten the nipple, the spoke length decreases,
but with a stiff rim, the ceiling acts like a completely rigid body, so the rim doesn't flex.
With a softer rim, it can't withstand the spoke tension
and flexes downward toward the floor.
This is my theory, but I think softer rims (a flexing ceiling) share the spoke tension
between the spoke and the rim, whereas
stiff rims (a rigid ceiling) make the spoke bear all the tension.
What I'm getting at is that using Revolution spokes on a stiff rim
might cause that stretching effect more easily than on a softer rim.
From my experience, this seems to be true.
As for what constitutes a "soft rim" here, there's no clear line,
but something like a Mavic GEL280 lightweight tube rim would qualify.
I think you could build that wheel well before the Revolution stretching effect becomes a problem.
↑That's the idea.
Most modern aluminum rims, including the Open Pro,
fall into the "stiff" category, and for those rims,
you'd run into the Revolution "stretching zone" before you could finish building the wheel.
The front wheel at the start had low spoke tension probably to stay below the stretching zone.
But nowadays, with CX-RAY having nearly the same relative density as Revolution
and almost no stretching effect across the normal hand-building range,
I don't understand why anyone would insist on using Revolution.
On another note, I was asked indirectly by a colleague recently:
"I tried building an Ambrosio Formula Crono 20 with Revolution spokes,
and the spokes just kept stretching—I couldn't finish the build."
The person in the middle helps me a lot, so I had to explain things candidly, including trade secrets.
The Crono 20 is lightweight but counts as a "stiff rim".
The amount of rim flex during break-in relative to its weight is remarkably minimal.
If they'd accept just "this rim and spoke combination aren't compatible"
without further explanation, they'd probably solve it themselves anyway.
So that's why I don't use Revolution spokes.
If there were a work-hardened spoke with Competition-equivalent density,
I might use that instead, but Competition so rarely exhibits stretching
that there's not really a problem. When it does happen (→here)
I've written much the same thing.
In that old post I listed Revolution's relative density as 64.2%,
while this article says 63.5%—different numbers. That's because
I measure relative density repeatedly, so it changes sometimes.
Below 70% of a 2.0mm plain spoke seems to be the line,
and below that, unwork-hardened spokes (like Sapim Laser) are prone to stretching,
so I basically don't use them.
Saying "prone to" makes it sound probabilistic, like
"sometimes it doesn't happen."
That's not it. Once you cross a certain threshold, it happens 100% of the time—
the threshold is just lower. That's what I mean by "prone to."
I adopt CX-RAY not for its aero performance.
Except for costing the customer more money (it's expensive!),
I don't see any way CX-RAY is inferior to Revolution.