Rim tolerance (runout) Question

Rob Weinstock said:

How flat should a new rim be?
I recently received a set of NOS rims in the mail. The box had obvious
shipping damage. When I hold the two rims together, brake surface to
brake surface, it's clear that one or both has some damage. However, it
is slight, only about 3mm of daylight appear between the rim edges,
which I can close with an easy squeeze of my fingers. Running my fingers
around the rim reveals no flats, creases, or other damage that would
make me automatically toss the rim.
So, is 3mm flat enough to result in a wheel that will have "even enough"
spoke tension? These are 36-hole Mavics, BTW.
Thanks and regards,
Rob

You can likely bend the rim(s) back flat. If they are some of the more
compliant Mavics it can be done by "hand" . It is difficult to know what
the spoke tension story will be until after you build them up. I have
built Sun rimmed wheels where the rims started flat to less than 0.05mm
and round to the same tolerance, but the rim wouldn't stay true to
within 0.5 mm when completed and tension balanced. If you are in a
situation of not easily returning them for a replacement, what other
alternatives were you considering? The methods described in Jobst
Brandt's book "the Bicycle Wheel" will work. Just take your time and use
an accurate "flat" for a standard.

--

Rob Weinstock said:

How flat should a new rim be?

Quoted message said:

I recently received a set of NOS rims in the mail. The box had
obvious shipping damage. When I hold the two rims together, brake
surface to brake surface, it's clear that one or both has some
damage. However, it is slight, only about 3mm of daylight appear
between the rim edges, which I can close with an easy squeeze of my
fingers. Running my fingers around the rim reveals no flats,
creases, or other damage that would make me automatically toss the
rim.

By that description, you should have no trouble building good wheels
with these rims. Don't bother doing anything to them other than
putting a dab of oil on the inside of each eyelet (there where the
spoke nipple will bear) and build wheels.

Jobst Brandt
[email hidden]

Quoted message said:

You can likely bend the rim(s) back flat. If they are some of the more
compliant Mavics it can be done by "hand" . It is difficult to know what
the spoke tension story will be until after you build them up. I have
built Sun rimmed wheels where the rims started flat to less than 0.05mm
and round to the same tolerance, but the rim wouldn't stay true to
within 0.5 mm when completed and tension balanced. If you are in a
situation of not easily returning them for a replacement, what other
alternatives were you considering? The methods described in Jobst
Brandt's book "the Bicycle Wheel" will work. Just take your time and use
an accurate "flat" for a standard.

Thanks for the response -- finding an accurate flat will be
interesting. I have a granite inspection stone, but it's only 18" x
12". Garage floors are notorious not flat.

These are vintage NOS rims, Mavic Record du Monde. Very pretty. My
choices are to use as-is; try my luck with an insurance claim; chuck
and try to find another; attempt to fix, then use.

I'm wondering how flat/round rims are from the factory? I mean, are
there standardized specs that are maintained, etc.?

Thanks and regards,

Rob

Quoted message said:

By that description, you should have no trouble building good wheels
with these rims. Don't bother doing anything to them other than
putting a dab of oil on the inside of each eyelet (there where the
spoke nipple will bear) and build wheels.

Thanks, that's reassuring.

Regards,

Rob

Rob Weinstock said:

Quoted message said:

By that description, you should have no trouble building good wheels
with these rims. Don't bother doing anything to them other than
putting a dab of oil on the inside of each eyelet (there where the
spoke nipple will bear) and build wheels.

Thanks, that's reassuring.
Regards,
Rob

Ritchey says "* High Tolerance Machined (+0.03mm)" for many of their
rims. I have seen similar results in Mavic rims and Velocity rims
although I have never see what they specify.

--

Quoted message said:

Quoted message said:

You can likely bend the rim(s) back flat.

-snip-

Rob Weinstock wrote:
finding an accurate flat will be

Quoted message said:

interesting. I have a granite inspection stone, but it's only 18" x
12". Garage floors are notorious not flat.

-snip-

Quoted message said:

I'm wondering how flat/round rims are from the factory? I mean, are
there standardized specs that are maintained, etc.?

Lay it on a true wheel.
Press it flat before you build it
New Rims arrive within a millimeter

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Andrew Muzi said:

Quoted message said:

Quoted message said:

You can likely bend the rim(s) back flat.

Quoted message said:

Quoted message said:

Finding an accurate flat will be interesting. I have a granite
inspection stone, but it's only 18" x 12". Garage floors are
notorious not flat.

Quoted message said:

Quoted message said:

I'm wondering how flat/round rims are from the factory? I mean,
are there standardized specs that are maintained, etc.?

Quoted message said:

Lay it on a true wheel. Press it flat before you build it New Rims
arrive within a millimeter

Pressing a rim against a flat surface will not remove wows that are
within the elastic limit of the rim. That means, greater than +-10mm.
As I said, if the rim is a smooth saddle then forget the wow and build
the wheel. That sort of misalignment is trivial to flatten and will
not affect performance. Kinks are another matter but I don't see that
a new rim will have kinks, they being impossible to create in
manufacture other than from a badly cut butt joint.

Jobst Brandt
[email hidden]

daveornee <[email hidden]> wrote;

Quoted message said:

Ritchey says "* High Tolerance Machined (+0.03mm)" for many of their
rims. I have seen similar results in Mavic rims and Velocity rims
although I have never see what they specify.

That's a misleading claim, because they do not specify which
dimensions are toleranced to that standard. Since they say
"machined", I assume the .03mm tolerance is on the width between brake
tracks. That's just over one thousandth of an inch-- serious
precision but not impossible in a mass-production setting.

It would be easy enough to hold width and perhaps brake track
parallelism to such a tolerance. I highly doubt any rim manufacturer
uses a similarly tight tolerance for flatness, roundness, diameter,
variation in wall thickness, drilling location, or even squareness at
the joint.

Keep in mind that a rim that starts out with a sub-.001" variation in
width is likely to meet this spec even when worn out and failed
structurally. It does not imply that the rim will be easy to build
into a true and durable wheel.

Chalo Colina

Rob Weinstock:

Quoted message said:

Quoted message said:

Quoted message said:

Finding an accurate flat will be interesting.

Andrew Muzi said:

Quoted message said:

Lay it on a true wheel. Press it flat before you build it New Rims
arrive within a millimeter

Quoted message said:

Pressing a rim against a flat surface will not remove wows that are
within the elastic limit of the rim. That means, greater than +-10mm.

I think Muzi meant to use a true wheel as an indicator, not as a surface
against which to straighten the rim.

Quoted message said:

...I don't see that
a new rim will have kinks, they being impossible to create in
manufacture other than from a badly cut butt joint.

The OP said this, way back at the beginning of the thread:

Quoted message said:

I recently received a set of NOS rims in the mail. The box had obvious
shipping damage.

I could imagine shipping damage causing kinks...

I concur with Jobst in that if no kinks are present, 3 mm runout seems
trivial to correct using spoke tension.

--
Dave
dvt at psu dot edu

Quoted message said:

Quoted message said:

Quoted message said:

>You can likely bend the rim(s) back flat.

Quoted message said:

Quoted message said:

Quoted message said:

Finding an accurate flat will be interesting. I have a granite
inspection stone, but it's only 18" x 12". Garage floors are
notorious not flat.
I'm wondering how flat/round rims are from the factory? I mean,
are there standardized specs that are maintained, etc.?

Quoted message said:

Andrew Muzi said:

Lay it on a true wheel. Press it flat before you build it New Rims
arrive within a millimeter

Quoted message said:

Pressing a rim against a flat surface will not remove wows that are
within the elastic limit of the rim. That means, greater than +-10mm.
As I said, if the rim is a smooth saddle then forget the wow and build
the wheel. That sort of misalignment is trivial to flatten and will
not affect performance. Kinks are another matter but I don't see that
a new rim will have kinks, they being impossible to create in
manufacture other than from a badly cut butt joint.

Jobst Brandt
[email hidden]

Ahh, the vagaries of English. I was overly terse it seems.

How to check if a rim is flat? Against another wheel is a
good quick way to see that.

I did not intend to imply that one should press a rim
_against a wheel_ to remove a bend. That's not possible. If
you inferrred that, it wasn't my intent at all. Across ones
knee is quicker.

Commonly when dealing with XMart bikes whose wheels will not
spin in the bike despite an attempt at truing, we press a
knee against the rim, bring up some tension and achieve a
functional wheel in a few minutes. That when even a couple
of dollars cannot be charged.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971