Wheel eccentricity -- where to look?

did you try belt conditioner as brake prep?

Mike Rocket J Squirrel said:

I am replacing the spokes on my wife's little road bike. The original
alloy nipples were starting to come apart so a complete rebuild is
required. I've only built a couple wheel sets before, and that was in
the late 70's, so I am hardly skilled in this area. Then, I didn't have
a tensiometer or a truing stand, but the wheels worked fine.

Anyways. The rear wheel is built up, dished and pretty true with no more
than a millimeter or so of side-to-side wobble, except for a wiggle at
the rim join. The tension on the spokes on each side are within 10 to
15% of each other. A little more adjusting should bring them closer
together, I think.

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why. The spokes all appear to extend
about the same length into the nipples all 'round, judging by the length
of exposed threads. If there is an improperly-seated spoke head I don't
see it. No mistakes in lacing found. I reckon that a spoke the wrong
length that made it into the bag could cause this, but otherwise, it
doesn't make much sense. So I'm overlooking something.

so, you replaced the spokes, but kept the old rim? If so, that is
likely why you have "hops" in the rim. That is what happens to wheels
over time. They take potholes etc.

On 10/19/2006 10:25 AM bill said:

Mike Rocket J Squirrel said:

I am replacing the spokes on my wife's little road bike. The original
alloy nipples were starting to come apart so a complete rebuild is
required. I've only built a couple wheel sets before, and that was in
the late 70's, so I am hardly skilled in this area. Then, I didn't have
a tensiometer or a truing stand, but the wheels worked fine.

Anyways. The rear wheel is built up, dished and pretty true with no more
than a millimeter or so of side-to-side wobble, except for a wiggle at
the rim join. The tension on the spokes on each side are within 10 to
15% of each other. A little more adjusting should bring them closer
together, I think.

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why. The spokes all appear to extend
about the same length into the nipples all 'round, judging by the length
of exposed threads. If there is an improperly-seated spoke head I don't
see it. No mistakes in lacing found. I reckon that a spoke the wrong
length that made it into the bag could cause this, but otherwise, it
doesn't make much sense. So I'm overlooking something.

so, you replaced the spokes, but kept the old rim? If so, that is
likely why you have "hops" in the rim. That is what happens to wheels
over time. They take potholes etc.

The wheels probably had no more than 200 miles on them (she usually
rides another bike) before the nipples started to disintegrate; and the
roads around here are not bad. Not perfect, though, as anyone who has
ridden Highway 1 in San Diego's North County will attest.

And it's certainly possible that this amount of eccentricity is nothing
to raise an eyebrow or two about. I don't know enough about
wheelbuilding . . . or wheelREbuilding, in this case, to judge whether I
am seeing a problem caused by unskillful work, or just the normal
tolerances found in midrange OEM parts -- in this case, Alexrims wheels
on Specialized road bike.

-- mike elliott

Mike Rocket J Squirrel said:

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why.

See:
http://sheldonbrown.com/wheelbuild.html#tensioning

Specifically the part where Sheldon says:
----------------
"For vertical truing, find the highest high spot on the rim. If the
center of this high spot is between two spokes, tighten each of them
1/2 turn. If the high spot is centered over one spoke, tighten that
spoke one full turn, and each of the two spokes next to it that go to
the other flange, 1/2 turn. It takes a larger adjustment to affect the
vertical truing than the horizontal truing. Vertical truing should
usually be done by tightening spokes, gradually building up the tension
in the wheel as you go along."
----------------

It's not unusual to have a hop at the rim joint. Or the rim may have
taken a "set." Tweak for the best combination of even tension and
roundness.

Art Harris

On 10/19/2006 12:59 PM Art Harris said:

Mike Rocket J Squirrel said:

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why.

See:
http://sheldonbrown.com/wheelbuild.html#tensioning

Specifically the part where Sheldon says:
----------------
"For vertical truing, find the highest high spot on the rim. If the
center of this high spot is between two spokes, tighten each of them
1/2 turn. If the high spot is centered over one spoke, tighten that
spoke one full turn, and each of the two spokes next to it that go to
the other flange, 1/2 turn. It takes a larger adjustment to affect the
vertical truing than the horizontal truing. Vertical truing should
usually be done by tightening spokes, gradually building up the tension
in the wheel as you go along."
----------------

It's not unusual to have a hop at the rim joint. Or the rim may have
taken a "set." Tweak for the best combination of even tension and
roundness.

Art Harris

"Best combination of even tension and roundness." I reckon another way
to put it is: "that's good enough!"

-- mike elliott

Mike Rocket J Squirrel said:

I am replacing the spokes on my wife's little road bike. The original
alloy nipples were starting to come apart so a complete rebuild is
required. I've only built a couple wheel sets before, and that was in
the late 70's, so I am hardly skilled in this area. Then, I didn't have
a tensiometer or a truing stand, but the wheels worked fine.

Anyways. The rear wheel is built up, dished and pretty true with no more
than a millimeter or so of side-to-side wobble, except for a wiggle at
the rim join. The tension on the spokes on each side are within 10 to
15% of each other. A little more adjusting should bring them closer
together, I think.

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why. The spokes all appear to extend
about the same length into the nipples all 'round, judging by the length
of exposed threads. If there is an improperly-seated spoke head I don't
see it. No mistakes in lacing found. I reckon that a spoke the wrong
length that made it into the bag could cause this, but otherwise, it
doesn't make much sense. So I'm overlooking something.

The rim isn't round is all. It gets deformed when riding. make it round
first, then tensioned.

Quoted message said:

--

mike elliott, who realizes that no matter how perfectly round a wheel
is, the road ain't flat.

Mike Elliott said:

On 10/19/2006 10:25 AM bill said:

Mike Rocket J Squirrel said:

I am replacing the spokes on my wife's little road bike. The original
alloy nipples were starting to come apart so a complete rebuild is
required. I've only built a couple wheel sets before, and that was in
the late 70's, so I am hardly skilled in this area. Then, I didn't have
a tensiometer or a truing stand, but the wheels worked fine.

Anyways. The rear wheel is built up, dished and pretty true with no more
than a millimeter or so of side-to-side wobble, except for a wiggle at
the rim join. The tension on the spokes on each side are within 10 to
15% of each other. A little more adjusting should bring them closer
together, I think.

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why. The spokes all appear to extend
about the same length into the nipples all 'round, judging by the length
of exposed threads. If there is an improperly-seated spoke head I don't
see it. No mistakes in lacing found. I reckon that a spoke the wrong
length that made it into the bag could cause this, but otherwise, it
doesn't make much sense. So I'm overlooking something.

so, you replaced the spokes, but kept the old rim? If so, that is
likely why you have "hops" in the rim. That is what happens to wheels
over time. They take potholes etc.

The wheels probably had no more than 200 miles on them (she usually
rides another bike) before the nipples started to disintegrate; and the
roads around here are not bad. Not perfect, though, as anyone who has
ridden Highway 1 in San Diego's North County will attest.

You are assuming the wheel was properly built to start with. With nipps
going south in 200 miles, I would doubt it. Poor builds of a wheel
could make it not round, poorly tensioned and a fewq rides could make
it deformed. If ya see this, but want a reliable wheel, get a new rim,
the thing that goes sounth, not spokes.

Quoted message said:

And it's certainly possible that this amount of eccentricity is nothing
to raise an eyebrow or two about. I don't know enough about
wheelbuilding . . . or wheelREbuilding, in this case, to judge whether I
am seeing a problem caused by unskillful work, or just the normal
tolerances found in midrange OEM parts -- in this case, Alexrims wheels
on Specialized road bike.

-- mike elliott

Qui si parla Campagnolo said:

Mike Elliott wrote:

Quoted message said:

Quoted message said:

Quoted message said:

> However, the wheel is not real concentric.

<snip>

Quoted message said:

You are assuming the wheel was properly built to start with. ...

<snip>

Nuh-uh. I never assumed the wheel was properly built to start with. I
would be blown away if that were so, especially at this price point. All
I can vouch for is that it was true enough to permit the brake pads to
run quite close to the rim because my wife has small pitifully weak
hands and everything was done to help her deal with man-sized brifter
levers.

No, if we're going to find the mistake(s) in my assumptions, I better
lay them out on the table:

1. With only 200 miles on it, and nothing like rough riding, I /assume/
the rim wasn't hammered.

2. After taking the wheel apart and re-building it, I /assume/ that
unless the rim was was damaged, it has little or no "memory" of how it
was built originally. It might not have come from the factory perfectly
flat or circular, but aluminum is pretty springy stuff, and see next:

3. I /assume/ that if the spokes are all the same length, and if they
are all inserted into the nipples to the same depth, and their tensions
are are pretty darn close, then the rim and the axle would be
concentric. In fact, I /assume/ it could not be otherwise.

4. I don't know whether a reasonably-well built wheel would demonstrate
3 to 4mm of eccentricity. At some point a wheel is "close enough" to
perfect roundness, but I /assume/ that this wheel is not "close enough,"
which is why I asked the question.

So, THOSE are the assumptions that I've made.

-- mike elliott, who assumes his assumptions are inaccurate.

mark the out of area-both sides and center
then either run it
or loosen spokes and redo
but! start with low torque-1/2 or 1/4 turn more or less than the other
spokes either at the area out of if for example too hi in roundness
with extra looseness at the other opposite side if the "area"is really
out of-this latter the acceptable method of radial perfection pursuit!!

Mike Rocket J Squirrel said:

Qui si parla Campagnolo said:

Mike Elliott wrote:

Quoted message said:

Quoted message said:

>> However, the wheel is not real concentric.

<snip>

Quoted message said:

You are assuming the wheel was properly built to start with. ...

<snip>

Nuh-uh. I never assumed the wheel was properly built to start with. I
would be blown away if that were so, especially at this price point. All
I can vouch for is that it was true enough to permit the brake pads to
run quite close to the rim because my wife has small pitifully weak
hands and everything was done to help her deal with man-sized brifter
levers.

No, if we're going to find the mistake(s) in my assumptions, I better
lay them out on the table:

1. With only 200 miles on it, and nothing like rough riding, I /assume/
the rim wasn't hammered.

2. After taking the wheel apart and re-building it, I /assume/ that
unless the rim was was damaged, it has little or no "memory" of how it
was built originally. It might not have come from the factory perfectly
flat or circular, but aluminum is pretty springy stuff, and see next:

3. I /assume/ that if the spokes are all the same length, and if they
are all inserted into the nipples to the same depth, and their tensions
are are pretty darn close, then the rim and the axle would be
concentric. In fact, I /assume/ it could not be otherwise.

4. I don't know whether a reasonably-well built wheel would demonstrate
3 to 4mm of eccentricity. At some point a wheel is "close enough" to
perfect roundness, but I /assume/ that this wheel is not "close enough,"
which is why I asked the question.

So, THOSE are the assumptions that I've made.

-- mike elliott, who assumes his assumptions are inaccurate.

It seems to me you are making a very reasonable conclusion based on some
geometry. But I'm reminded of Einstein's saying that "As far as the
laws of mathematics refer to reality, they are not certain, and as far
as they are certain, they do not refer to reality." In other words, I
agree it's how things seemingly should be, but they ain't.

In my experience these sorts of failures of theory usually boil down to
some overlooked detail - perhaps variations in rim thickness at the
spoke hole (admittedly a wild guess).

Just adjust the spokes as others have suggested (the advice on Sheldon's
site works), or accept the seemingly "wrong" eccentricity.

On the other hand, if the point of your post is just to present RBT with
a puzzler, then job well done.

Mark J.

Mark said:

It seems to me you are making a very reasonable conclusion based on some
geometry. But I'm reminded of Einstein's saying that "As far as the
laws of mathematics refer to reality, they are not certain, and as far
as they are certain, they do not refer to reality." In other words, I
agree it's how things seemingly should be, but they ain't.

Oh. It's one of those. Okay, the world is filled with mysterious and
wondrous phenomena, like Paris Hilton's fame, the anthropic principle,
and how I have 200 channels on cable yet not find a single thing to
watch. I'm perfectly happy to file this into that category.

<snip>

Quoted message said:

On the other hand, if the point of your post is just to present RBT with
a puzzler, then job well done.

I like posing a good puzzler as much as the next guy, so thanks!

-- mike elliott

Mike Rocket J Squirrel said:

However, the wheel is not real concentric. It has about 3 to 4mm of
eccentricity and I can't figure out why. The spokes all appear to extend
about the same length into the nipples all 'round, judging by the length
of exposed threads. If there is an improperly-seated spoke head I don't
see it. No mistakes in lacing found. I reckon that a spoke the wrong
length that made it into the bag could cause this, but otherwise, it
doesn't make much sense. So I'm overlooking something.

If everything you wrote is accurate and the wheel seem elyptical, than
you might have a bent hub axel or bad hub.

Mike Elliott said:

Quoted message said:

It's not unusual to have a hop at the rim joint. Or the rim may have
taken a "set." Tweak for the best combination of even tension and
roundness.

Art Harris

"Best combination of even tension and roundness." I reckon another way
to put it is: "that's good enough!"

Not necessarily. If the rim itself is not round (which could be due to
a variety of reasons, including being badly built initially), you will
never get it perfectly round with even tension. But you may be able to
make it better than it is by careful truing. At worst, I'd shoot for
2mm of variation in roundness and 10 percent variation in spoke
tension. If you can't get that, either try straightening the rim (See:
The Bicycle Wheel) or replace it.

Art Harris

Art Harris said:

Mike Elliott said:

Quoted message said:

It's not unusual to have a hop at the rim joint. Or the rim may have
taken a "set." Tweak for the best combination of even tension and
roundness.

Art Harris

"Best combination of even tension and roundness." I reckon another way
to put it is: "that's good enough!"

Not necessarily. If the rim itself is not round (which could be due to
a variety of reasons, including being badly built initially), you will
never get it perfectly round with even tension. But you may be able to
make it better than it is by careful truing. At worst, I'd shoot for
2mm of variation in roundness and 10 percent variation in spoke
tension. If you can't get that, either try straightening the rim (See:
The Bicycle Wheel) or replace it.

Art Harris

Hey Art: thanks for providing some target values! Now I know what to
shoot for.

-- mike elliott