mavic rims don't *all* suck

Discussion in 'Cycling Equipment' started by Dvt, Feb 26, 2004.

  1. Jobst Brandt

    Jobst Brandt Guest

    Dave vt? writes:

    >> This is for most rims an insignificant load unless there are crack initiators. As I have
    >> mentioned, I have ridden MA-2 rims until sidewalls were worn down to 0.5mm (0.020") with no
    >> failure.

    > These sidewalls are ~1.5-1.8 mm thick at the crack.

    > How do you know when to replace a rim? Concavity in the brake wall? Do you measure the wall
    > thickness? Based on your earlier post, I don't think you wait until they crack.

    I have a calibrated thumb and forefinger that I pass over the rim in a brake caliper manner feeling
    the hollow cheeks of the rim. I know how .5mm wall feels. On a tour of the Alps on which it rained
    on almost every major descent. I noticed at the top of the Stelvio that I was at the limit on the
    front rim. Because it was raining, I could not use the front brake, so I used only the rear brake to
    descend. Afterwards, in the flatland, as soon as the road was dry, I could use the front brake
    again, because practically no wear occurs when dry with Kool-Stop Salmon red pads because they don't
    get grit inclusions. I have a section of that and other rims, in my collection.

    Jobst Brandt [email protected]
     


  2. carlfogel

    carlfogel New Member

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    Dear Jobst,

    Hmm . . . it might have been safer to back down the
    Stelvio, like a Model T taking advantage of its unworn
    reverse.

    Analysis reveals unmistakable humor inclusions.

    But don't quit your day job(st).

    Thumbs up,

    Carl Fogel
     
  3. Werehatrack

    Werehatrack Guest

    On Sat, 28 Feb 2004 00:01:28 +0100, "SMMB"
    <[email protected]> may have said:

    >
    >"dvt" <[email protected]> a √©crit dans le message de : news:[email protected]...
    >> Werehatrack wrote:
    >> > Despite the long period in service, I have to say that I'm not impressed..............
    >
    >
    >> Same question to you: How do you tell when a brake wall is too thin for continued service?
    >>
    >
    >I think all the Mavic haters really believe that a virtuous rim gives its soul to the hereafter,
    >collapses into a pile of pixie-dust, having left a note of regret.
    >
    >Now that's the right failure mode ? Everything fails, somehow, sometime. Same crowd, I would bet,
    >that is wistful for the days of washable oil filters for cars...

    Aluminum rims appear not to have a "right" failure mode, but given that the indestructible steel
    rims also had the distinct disadvantage of being lousy as brake components, failure seems to be the
    lot we must accept. What I don't see is why the brake surfaces of the rims aren't made a bit thicker
    on some wheels (leaving, of course, some with lighter weight for those whose preference is for
    lightness over durability) with a marked and measurable wear limit in the same way that such a
    specification is given for the brake discs on automobiles.

    --
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  4. Werehatrack

    Werehatrack Guest

    On Fri, 27 Feb 2004 16:46:21 -0500, dvt <[email protected]> may have
    said:

    >Werehatrack wrote:
    > > Have you inspected the flanges on the *inside*
    >> for signs of cracks around the rest of the circumference of the wheel? I'm betting that you'll
    >> find that you have more than just the two which precipitated the failures.
    >
    >I don't see any cracks. The inside of the flanges is pretty gooped up with Velox adhesive, so the
    >cracks may be disguised.

    That's quite possible. It's probably academic, though, since the rim is obviously going to be out of
    service anyway. Even if there were cracks that could have been found, it's unlikely that they would
    have been spotted prior to the failure since it's not like you're going to rip a good sew-up off of
    the wheel just to inspect the flanges periodically.

    --
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  5. Matt O'Toole

    Matt O'Toole Guest

    Werehatrack wrote:

    > Aluminum rims appear not to have a "right" failure mode,

    What does this mean?

    > but given that the indestructible steel rims also had the distinct disadvantage of being lousy as
    > brake components, failure seems to be the lot we must accept. What I don't see is why the brake
    > surfaces of the rims aren't made a bit thicker on some wheels (leaving, of course, some with
    > lighter weight for those whose preference is for lightness over durability) with a marked and
    > measurable wear limit in the same way that such a specification is given for the brake discs on
    > automobiles.

    This is exactly what we have. Some rims are thick (and heavier), some are light (and thinner), and
    nowadays rims have wear indicators molded into the sidewalls (as required by law in Europe, IIRC).
    Previously, one could determine wear by measuring.

    The whole point of this thread is that no matter how thick the sidewalls, rims no longer last until
    the wear limit is reached -- they crack first.

    Matt O.
     
  6. Jim Beam

    Jim Beam Guest

    Matt O'Toole wrote: <snip

    >
    > The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    > until the wear limit is reached -- they crack first.
    >
    is this a fact? what testing have you done? what were your controls?
     
  7. Tim McNamara

    Tim McNamara Guest

    Werehatrack <[email protected]> writes:

    > On Sat, 28 Feb 2004 00:01:28 +0100, "SMMB" <[email protected]> may have said:
    >
    >>Now that's the right failure mode ? Everything fails, somehow, sometime.
    >
    > Aluminum rims appear not to have a "right" failure mode

    The "right" failure mode is one that is predictable and non-catastrophic. Non-anodized and socketed
    aluminum rims have the right failure mode in that failure is predictable from braking area wear.
    Anodized rims, introducing new catastrophic failure modes, do not have the "right" failure mode.
     
  8. Tim McNamara

    Tim McNamara Guest

    jim beam <[email protected]> writes:

    > Matt O'Toole wrote: <snip
    >
    >> The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    >> until the wear limit is reached -- they crack first.
    >>
    > is this a fact? what testing have you done? what were your controls?

    You haven't been reading along, have you? Or are you just pretending to be dense?
     
  9. Carl Fogel

    Carl Fogel Guest

    "Matt O'Toole" <[email protected]> wrote in message news:<[email protected]>...

    [snip worthy werehatrack brake-wear indicator suggestion]

    >
    > The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    > until the wear limit is reached -- they crack first.
    >
    > Matt O.

    Dear Matt,

    You may need to explain what you mean. (Try to be patient with everyone who jumps on you.)

    Are you saying that you expect anodized rims to crack elsewhere before the rims fail because of
    brake wear? (Cracks, for example, around spoke holes, or cracks around the rim not related to brake-
    worn areas. Are there such cracks in these pictures?)

    Or do you expect anodized rims to crack in the brake area before normal brake wear should ruin them?
    (Anodizing is usually removed from brake areas, either by the machining process or else by normal
    brake wear, but it might somehow still be involved.)

    Despite its title, this thread has no point. Dave just asked us all to look at pictures of his
    failed rim and to try to figure out why it failed. Is the culprit anodization, brake wear, a
    combination of the two, or something else?

    Personally, I think that an awful lot of questions need to be asked about Dave's sons. The sudden
    failure of metal objects, including anvils, is often noticed when children appear.

    Carl Fogel
     
  10. Mike S.

    Mike S. Guest

    "Tim McNamara" <[email protected]> wrote in message
    news:[email protected]...
    > Werehatrack <[email protected]> writes:
    >
    > > On Sat, 28 Feb 2004 00:01:28 +0100, "SMMB" <[email protected]> may have said:
    > >
    > >>Now that's the right failure mode ? Everything fails, somehow, sometime.
    > >
    > > Aluminum rims appear not to have a "right" failure mode
    >
    > The "right" failure mode is one that is predictable and non-catastrophic. Non-anodized and
    > socketed aluminum rims have the right failure mode in that failure is predictable from braking
    > area wear. Anodized rims, introducing new catastrophic failure modes, do not have the "right"
    > failure mode.

    'scuse me again. Most of the cracks we've discussed here aren't catastrophic in nature.

    If I'm mistaken, please correct me. Eyelets coming thru the rims, cracks radiating outward from the
    holes the eyelets sit in, etc. yes, but IIRC there were only two cases of "whoops! My rims went
    bang!" and both of those were older rims...

    I don't remember if my RM20s were anodized or not. I had the sidewalls blow out from being too thin.
    Appx a 6" section of brake track pulled away from the rest of the rim. I could tell that they were
    on their last legs 'cause the brake track was concave.

    Being a broke college student, I figured I'd ride them till they broke anyway.

    Mike
     
  11. Jim Beam

    Jim Beam Guest

    ok tim, explain what i'm missing.

    or are you just trying to pick a fight?

    Tim McNamara wrote:
    > jim beam <[email protected]> writes:
    >
    >
    >>Matt O'Toole wrote: <snip
    >>
    >>
    >>>The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    >>>until the wear limit is reached -- they crack first.
    >>>
    >>
    >>is this a fact? what testing have you done? what were your controls?
    >
    >
    > You haven't been reading along, have you? Or are you just pretending to be dense?
     
  12. Matt O'Toole

    Matt O'Toole Guest

    Carl Fogel wrote:

    > Are you saying that you expect anodized rims to crack elsewhere before the rims fail because of
    > brake wear? (Cracks, for example, around spoke holes, or cracks around the rim not related to brake-
    > worn areas. Are there such cracks in these pictures?)
    >
    > Or do you expect anodized rims to crack in the brake area before normal brake wear should ruin
    > them? (Anodizing is usually removed from brake areas, either by the machining process or else by
    > normal brake wear, but it might somehow still be involved.)

    I expect rims to not crack at all, and be serviceable until retired from brake wear, or crashed.
    This has been covered ad infinitum -- if not in this particular thread, then in the one it came from
    -- and in this newsgroup, for over a decade.

    > Despite its title, this thread has no point. Dave just asked us all to look at pictures of his
    > failed rim and to try to figure out why it failed. Is the culprit anodization, brake wear, a
    > combination of the two, or something else?

    That's a fatigue failure, and the third picture makes me suspect the anodizing played a part.

    > Personally, I think that an awful lot of questions need to be asked about Dave's sons. The sudden
    > failure of metal objects, including anvils, is often noticed when children appear.

    Yes, but one could still determine whether said failure was due to fatigue.

    Matt O.
     
  13. carlfogel

    carlfogel New Member

    Joined:
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    241
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    0
    Dear Matt,

    You wrote, "I expect rims to not crack at all, and be
    serviceable until retired from brake wear, or crashed."

    But Dave's point is that his rim may have gone past
    the point when it should have been retired due to
    brake wear and may therefore have cracked--he
    can't tell whether it's anodizing or just worn out.

    How would the two kinds of cracks differ?

    What is it about the third picture that makes you
    suspect that the anodizing played a part?

    That's what Dave is interested in. (Well, that and
    exonerating his sons.)

    Carl Fogel
     
  14. Tim McNamara

    Tim McNamara Guest

    "Mike S." <[email protected]> writes:

    > "Tim McNamara" <[email protected]> wrote in message news:[email protected]...
    >
    >> Werehatrack <[email protected]> writes:
    >>
    >> > On Sat, 28 Feb 2004 00:01:28 +0100, "SMMB" <[email protected]> may have said:
    >> >
    >> >>Now that's the right failure mode ? Everything fails, somehow, sometime.
    >> >
    >> > Aluminum rims appear not to have a "right" failure mode
    >>
    >> The "right" failure mode is one that is predictable and non-catastrophic. Non-anodized and
    >> socketed aluminum rims have the right failure mode in that failure is predictable from braking
    >> area wear. Anodized rims, introducing new catastrophic failure modes, do not have the "right"
    >> failure mode.
    >
    > 'scuse me again. Most of the cracks we've discussed here aren't catastrophic in nature.

    Because they were spotted in time.

    > If I'm mistaken, please correct me. Eyelets coming thru the rims, cracks radiating outward from
    > the holes the eyelets sit in, etc. yes, but IIRC there were only two cases of "whoops! My rims
    > went bang!" and both of those were older rims...

    Eyelets coming through the rim would be catastrophic failure, quite possibly rendering the wheel
    instantly unrideable and potentially causing the wheel to lock up. Not the best situation if you're
    riding in heavy traffic or descending a mountain road at the time, or at any time if it's the front
    wheel. Or if you're 60 miles into a 120 mile ride. You've apparently missed the references to other
    catstrophic rim failures that have been mentioned in connection to hard andized rims in particular
    (not surprising given the stupendous length of this thread; I've not read every post and skipped the
    ones about asphalt almost entirely).

    > I don't remember if my RM20s were anodized or not. I had the sidewalls blow out from being too
    > thin. Appx a 6" section of brake track pulled away from the rest of the rim. I could tell that
    > they were on their last legs 'cause the brake track was concave.

    In which case you had advance warning- hence the "right" failure mode.

    > Being a broke college student, I figured I'd ride them till they broke anyway.

    Not only broke but apparently having little regard for your own safety.
     
  15. Jobst Brandt

    Jobst Brandt Guest

    Werehatrack <[email protected]> writes:

    >>> Have you inspected the flanges on the *inside* for signs of cracks around the rest of the
    >>> circumference of the wheel? I'm betting that you'll find that you have more than just the two
    >>> which precipitated the failures.

    >> I don't see any cracks. The inside of the flanges is pretty gooped up with Velox adhesive, so the
    >> cracks may be disguised.

    > That's quite possible. It's probably academic, though, since the rim is obviously going to be out
    > of service anyway. Even if there were cracks that could have been found, it's unlikely that they
    > would have been spotted prior to the failure since it's not like you're going to rip a good sew-up
    > off of the wheel just to inspect the flanges periodically.

    As far as I could see, this is a clincher rim and the crack should be detectable on the outside when
    it first developed. As was mentioned, it grew and failed while parked, so it must have been there
    before it was parked. In any case, with many years of no anodized rims, such failures did not occur
    to any of the many bikies in our area. In contrast, with the advent of dark anodized rims, they
    occurred often.

    Jobst Brandt [email protected]
     
  16. Jobst Brandt

    Jobst Brandt Guest

    Matt O'Toole writes:

    >> Aluminum rims appear not to have a "right" failure mode,

    > What does this mean?

    >> but given that the indestructible steel rims also had the distinct disadvantage of being lousy as
    >> brake components, failure seems to be the lot we must accept. What I don't see is why the brake
    >> surfaces of the rims aren't made a bit thicker on some wheels (leaving, of course, some with
    >> lighter weight for those whose preference is for lightness over durability) with a marked and
    >> measurable wear limit in the same way that such a specification is given for the brake discs on
    >> automobiles.

    > This is exactly what we have. Some rims are thick (and heavier), some are light (and thinner), and
    > nowadays rims have wear indicators molded into the sidewalls (as required by law in Europe, IIRC).
    > Previously, one could determine wear by measuring.

    > The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    > until the wear limit is reached -- they crack first.

    Oh Matt, you blaspheme. You seem to have sold your heart to the technical opposition. The anodizing
    Mafia will get on your case.

    Jobst Brandt [email protected]
     
  17. Jobst Brandt

    Jobst Brandt Guest

    Carl Fogel writes:

    >> The whole point of this thread is that no matter how thick the sidewalls, rims no longer last
    >> until the wear limit is reached -- they crack first.

    > Dear Matt,

    > You may need to explain what you mean. (Try to be patient with everyone who jumps on you.)

    > Are you saying that you expect anodized rims to crack elsewhere before the rims fail because of
    > brake wear? (Cracks, for example, around spoke holes, or cracks around the rim not related to brake-
    > worn areas. Are there such cracks in these pictures?)

    > Or do you expect anodized rims to crack in the brake area before normal brake wear should ruin
    > them? (Anodizing is usually removed from brake areas, either by the machining process or else by
    > normal brake wear, but it might somehow still be involved.)

    The rim in question was not worn thin, certainly not thin enough to fail from the experience I have
    with observing anodized rim failures at local bicycle shops and among the riders with whom I have
    ridden. The cross section of the failed subject rim is evident from the separation photos that show
    at least 1mm thickness.

    > Despite its title, this thread has no point. Dave just asked us all to look at pictures of his
    > failed rim and to try to figure out why it failed. Is the culprit anodization, brake wear, a
    > combination of the two, or something else?

    He also made the claim in contrast to other postings that these rims do not fail in a dange4ous
    manner. That is the bone of contention. I brought that up and there is apparently no argument with
    my contention that this is as dangerous a failure as one can encounter. To visualize the danger one
    must either ride in traffic or descend mountain roads that border precipices.

    > Personally, I think that an awful lot of questions need to be asked about Dave's sons. The sudden
    > failure of metal objects, including anvils, is often noticed when children appear.

    Is this an attempt at humor or are you insinuating that Dave is blind to hazards?

    Jobst Brandt [email protected]
     
  18. Werehatrack

    Werehatrack Guest

    On Sun, 29 Feb 2004 06:20:25 GMT, [email protected] may
    have said:

    >Carl Fogel writes:

    >> Personally, I think that an awful lot of questions need to be asked about Dave's sons. The sudden
    >> failure of metal objects, including anvils, is often noticed when children appear.
    >
    >Is this an attempt at humor or are you insinuating that Dave is blind to hazards?

    I'm sure it was in jest. Merely mentioning anvils and children in the same utterance is a strong
    indicator. (And here I was thinking that you'd begun to grow a sense of humor...perhaps it just
    needs a bit more cultivating, you've actually managed to be witty more than a few times lately.
    Don't stop now!)

    --
    My email address is antispammed; pull WEEDS if replying via e-mail.
    Typoes are not a bug, they're a feature.
    Words processed in a facility that contains nuts.
     
  19. Jim Beam

    Jim Beam Guest

    Matt O'Toole wrote:
    > Carl Fogel wrote:
    >
    >
    >>Are you saying that you expect anodized rims to crack elsewhere before the rims fail because of
    >>brake wear? (Cracks, for example, around spoke holes, or cracks around the rim not related to brake-
    >>worn areas. Are there such cracks in these pictures?)
    >>
    >>Or do you expect anodized rims to crack in the brake area before normal brake wear should ruin
    >>them? (Anodizing is usually removed from brake areas, either by the machining process or else by
    >>normal brake wear, but it might somehow still be involved.)
    >
    >
    > I expect rims to not crack at all, and be serviceable until retired from brake wear, or crashed.
    > This has been covered ad infinitum -- if not in this particular thread, then in the one it came
    > from -- and in this newsgroup, for over a decade.

    be practical matt. when a rim has worn to its failure "thiness" it's going to fail - there's nothing
    you can do to stop it other than arrest the wear in the first place - that's what ceramic rims are
    for, but again, thay get so roundly condemned on this forum by those that have never used them, it
    makes it almost impossible to have rational debate.

    in regard to "acceptable" failure modes, what would work for you? even the cast iron brake disks on
    your car will crack when they get thin enough.

    >
    >
    >>Despite its title, this thread has no point. Dave just asked us all to look at pictures of his
    >>failed rim and to try to figure out why it failed. Is the culprit anodization, brake wear, a
    >>combination of the two, or something else?
    >
    >
    > That's a fatigue failure, and the third picture makes me suspect the anodizing played a part.

    with respect, there's nothing evident from those pics that allows a definite conclusion of that
    nature - there's not enough resolution to definitively confirm fatigue, nor any of the other
    possible failure modes for that matter. the fracture surface is arguably intergranular, which is
    /not/ typical of fatigue progression, but again, better resolution is required to be sure. beyond
    that, it's guesswork & conjecture.

    >
    >
    >>Personally, I think that an awful lot of questions need to be asked about Dave's sons. The sudden
    >>failure of metal objects, including anvils, is often noticed when children appear.
    >
    >
    > Yes, but one could still determine whether said failure was due to fatigue.

    with proper analysis, yes, but with all due respect to the op's artwork, there is nothing here that
    is sufficient for that conclusion.

    >
    > Matt O.
     
  20. Werehatrack

    Werehatrack Guest

    On Sun, 29 Feb 2004 05:50:56 GMT, carlfogel
    <[email protected]> may have said:

    >[Matt] wrote, "I expect rims to not crack at all, and be serviceable until retired from brake wear,
    >or crashed."
    >
    >But Dave's point is that his rim may have gone past the point when it should have been retired
    >due to brake wear and may therefore have cracked-- he can't tell whether it's anodizing or just
    >worn out.

    As observed by Jobst Brandt, the wear present would not seem sufficient to judge the rim past
    reasonable limits in that area. I agree with his assessment based on the photos. As such, the rim's
    failure seems premature.

    >How would the two kinds of cracks differ?

    I would expect a failure due to wear to be a shearing break, without the granularity present in the
    photos; the granularity indicates a crack which developed due to flexing or bending.

    >What is it about the third picture that makes you suspect that the anodizing played a part?

    I can't answer for anyone but myself, but I'd have to see some different data before I could
    eliminate the possibility that the anodization was a factor. From what's present, all *I* can say is
    that it looks like a crack formed in a flange that did not have excessive wear, that the crack looks
    to me like it began at the inner surface and migrated outward, and that it appears that it was not
    due to a sudden failure. This is consistent with, among other things, a crack that followed a stress
    riser of the type that could have formed due to etching of the metal during the anodizing process. I
    have observed over the years that extrusions etched with acids sometimes have a linear grain which
    can be brought out readily; the resulting ridged/grooved surface creates many small stress risers.
    Such a stress riser might take a long time to be revealed by a failure. I can't say if that's the
    mechanism of failure for the wheel in question, but I can't rule it out, and it's consistent with
    the available data.

    >That's what Dave is interested in. (Well, that and exonerating his sons.)

    Unless his sons have an Acme catalog, I doubt that they're going to have been involved. ("If it's
    not an ACME anvil, it's not funny!")

    --
    My email address is antispammed; pull WEEDS if replying via e-mail.
    Typoes are not a bug, they're a feature.
    Words processed in a facility that contains nuts.
     
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