Rim tolerance (runout) Question

Quoted post said:

Originally posted by Rob Weinstock
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

Quoted post said:

Originally posted by Rob Weinstock
> By that description, you should have no trouble building

Quoted message said:

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