Rim tolerance (runout) Question

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

daveornee

Rob Weinstock wrote:
> 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.



--

jobst.brandt@stanfordalumni.org

Rob Weinstock writes:

> 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.

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
jobst.brandt@stanfordalumni.org

Rob Weinstock

> 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

Rob Weinstock

> 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

daveornee

Rob Weinstock wrote:
> > 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.



--

A Muzi

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

Rob Weinstock wrote:
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.
-snip-
> 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

jobst.brandt@stanfordalumni.org

Andrew Muzi writes:

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

>> 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.?

> 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
jobst.brandt@stanfordalumni.org

Chalo

daveornee <usenet-forum@cyclingforums.com> wrote;

> 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

dvt

Rob Weinstock:
>>>Finding an accurate flat will be interesting.

Andrew Muzi writes:
>>Lay it on a true wheel. Press it flat before you build it New Rims
>>arrive within a millimeter

jobst.brandt@stanfordalumni.org wrote:
> 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.

> ...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:
> 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