Mavic MA-40 - Piece of Crap? - Page 7

On Thu, 25 Dec 2003 02:43:10 GMT, Ted Bennett
<tedbennett@earthlink.net> wrote:

>Please let us know your arguments in favor of machined rims.

I'm not in favor of welding, I'm in favor of good rims.

> Please address the effects of the weld on strength an durability of the alloy used.

I believe the weld affected zone is relatively small. And even though welding surely weakens the
rim, I can't imagine it weakening the rim more than the valve hole. As well, the weld usually has an
alignment spud or pins which probably reinforce the welded area.

> Compare the weights of machined rims versus unmachined rims.

Here I can't imagine welded rims coming out ahead, all else the same.

>Compare the cost to produce,

Remember also to consider the cost to
1. sell the rims
2. replace wheels and rims under warranty

. especially considering the large number of consumers (and shops) who believe "welded rims are
better" and will send back any non-welded rim that's mis-aligned, even though a responsible wheel
builder could easily fix it.

Also, what do you do for a sleeved rim that creaks? Replace the wheels under warranty?

Also consider the added cost to
3. train wheel builders of mass-produced wheels to spot and correct a mis aligned joint in wheels
built using non-welded rims.

> and consider the cost against the simple procedures used, or not used, to eliminate an uneven
> rim seam.

I would think manufacturing sleeved rims should be less expensive. But Manufacturing is not the only
cost -- see above.

"jim beam" <uce@ftc.gov> wrote in message
news:0L1Hb.2321$W67.1691@newssvr27.news.prodigy.com...
> jim beam wrote:
>
> <snip>
>
> >> Does anodizing significantly weaken aluminum parts like rims, handlebars, and so forth? How?
> >
> >
> > assuming that anodizing is the /only/ variable, it makes no difference to static strength but it
> > does to fatigue. it's the relevance that is debatable. if you have a rim whose braking surfaces
> > wears through in say 25,000 miles, how relevant is it that anodizing may reduce fatigue life
> > from 50,000 miles to 45,000 miles?
> >
>
> sorry, forgot the "how". anodizing can decrease fatigue performance because if it cracks, those
> cracks act as stress concentrations. fatige can then initiate at those points.
>
> but conversely, anodizing can protect significantly agains wear and corrosion and that can enhance
> fatigue life.

I found no difference in sidewall longevity between the Mod
E/Gentleman/E2/MA2 and G40/GP4/MA40. I did notice that most of the anodizing on the sidewalls was
gone within days or weeks of daily riding in the rain. I also noticed that the anodized rims had a
much higher incidence of cracking around the spoke holes. I also found no significant difference
in braking between any of these old rims (including some old dimpled Super Champ Mod 52s) and the
modern machined uber-rims. The only problem I ever had with bad breaking surfaces was when I wore
through the sidewalls, or was sloppy with rim cement -- but even that did no throw me over the
bars. Machining is another one of those solutions in search of a problem. -- Jay Beattie.

On Fri, 26 Dec 2003 10:28:35 +0000, Carl Fogel wrote:

> Which kind of rims provide better caliper braking, constant or varying width? How much better?
> That is, at what point does varying rim width become noticeable when braking?
>
You're not asking the right question. You assume that the machining of the rim is done to make the
width more uniform. You also assume that the machining makes a uniform rim. But machined sidewalls
only came about after rims were anodized. If a non-machined rim was so uneven, it would have been a
very good idea to machine it smooth even before they were anodized.

The rims are machined to scrape off the anodized surface from the braking flats, since anodizing on
the flats ruins the braking performance.

--

David L. Johnson

__o | Some people used to claim that, if enough monkeys sat in front _`\(,_ | of enough
typewriters and typed long enough, eventually one of (_)/ (_) | them would reproduce the
collected works of Shakespeare. The internet has proven this not to be the case.

David L. Johnson wrote:
> The rims are machined to scrape off the anodized surface from the braking flats

that may appear to be the case if you only look at part of the picture, but it takes no account of
"cd" rims that are anodized /after/ machining.

machining is for two reasons:

1. ensure the braking surface is uniform for the full circumference, particularly in the case of a
welded seam.

2. ensure brakes on new bikes work with full effect straight off the showroom floor - brake pads do
not have to wear themselves into conformity with the rim profile.

both these keep lawyers happy/unhappy, depending on which side of the accident lawsuit you sit.

>, since anodizing on the flats ruins the braking performance.

where did you read that? absolutely not. but don't believe me - go check some cd wheels out at your
lbs and ride them for yourself.

jb

Your assumption is wrong. Machined rims can still be anodized after the machining. Machining is NOT intended for scraping off the anodization. It is meant for uniformity and to smooth out an otherwise uneven seam. Machined rims are much more smoooooth than the old unmachined and seamed rims. That is fact.

jobst.brandt@stanfordalumni.org wrote in message news:<5h1Hb.5031$XF6.110358@typhoon.sonic.net>...
> Carl Fogel writes:
>
> > Dear Jobst and Jim,
>
> > As a bewildered layman, I'd like to ask a few obvious questions in hopes of learning more about
> > what I thought was the subject.
>
> Please stop this pseudo self deprecating style. Just ask the question.
>
> > Which kind of rims provide better caliper braking, constant or varying width? How much better?
> > That is, at what point does varying rim width become noticeable when braking?
>
> I think that should be apparent. A step function, such as a lateral shift at a non-welded rim
> joint causes an audible but non-functional brake noise. A sudden necking of the rim, in contrast,
> assuming average friction in the brake cable, would make a pulsating brake retardation. However, a
> change in rim width of a millimeter in a continuous cross section would not cause as much brake
> variation as a drop of water on the rim, something commonly encountered by bicyclists.
>
> > How much material is actually removed from machined rims compared to how much is left? Do
> > manufacturers compensate by making such rims thicker before machining, just as toilets are made
> > oversize to compensate for the way that they shrink in the kilns? (Sorry, but comparing rims to
> > toilets was irresistible.)
>
> I don't know anything about these cross sections, having only seen them displayed.
>
> > Does anodizing significantly weaken aluminum parts like rims, handlebars, and so forth? How?
>
> No, it doesn't but as I have often mentioned, it is a hard crust, just like a scab on a wound that
> when stressed, cracks and causes bleeding on your knee or causes cracks to propagate into the
> aluminum. Crack initiation is what causes the rim to fail and I use the scab analogy to make that
> palpable for those who cannot play the Maxwell's demon and get right down into the psyche of the
> metal surface.
>
> > How does anodizing affect braking, regardless of how the width of the rim varies?
>
> I thought you were the wizard of Google searches. This has been beat to death many times but it
> seems to have more lives than a cat squared.
>
> Anodizing is a ceramic insulator about half the density of aluminum, anodizing eats into the
> surface about as much as it raises the surface of an aluminum extrusion. Heat in a friction pair
> is generated in the surface of the softer material, in this case the "rubber" brake pad that is
> itself an excellent insulator. Its only coolant is the aluminum rim that is an excellent
> conductor, has large surface area, and is moving swiftly through the cooling medium, the
> atmosphere.
>
> By coating the rim with ceramic, its heat absorption is diminished. Even a thin layer considering
> the short residency of the pad at any location, looks to the hot surface of the brake pad like a
> mirror, accepting little to no heat. Therefore, the surface temperature of the pad becomes hotter
> than it normally would and thereby loses its designed drag coefficient against the braking
> surface. For rim protection some dirt bike rims have ceramic coatings but require a different
> brake pad that can take the heat. They also don't brake as well as common brakes when dry.
>
> > Curiously,
>
> I suppose.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org

Dear Jobst,

It's interesting to a layman how differently you and Jim Beam answer these questions. Neither of you
can resist a quick dig, but then you both promptly settle down to what seem like good points
emphasizing different approaches.

It takes a layman a while to ponder them.

I take it that you expect little practical effect from typical unmachined rims because the variation
is so slight (a drop of water), that you expect anodized surfaces to crack under stress (like thin
scabs) and for these surface cracks to possibly initiate deeper rim cracks, and that you expect
anodized rims to act as insulators, heat up brake pads, and reduce braking efficiency, which wasn't
as good as ordinary surfaces to begin with.

Thanks for your explanations.

Carl Fogel

jim beam <uce@ftc.gov> wrote in message news:<yw1Hb.2318$2%6.1853@newssvr27.news.prodigy.com>...
> Carl Fogel wrote:
> > jobst.brandt@stanfordalumni.org wrote in message
> > news:<%FHGb.4939$XF6.108373@typhoon.sonic.net>...
> >
> > Dear Jobst and Jim,
> >
> > As a bewildered layman, I'd like to ask a few obvious questions in hopes of learning more about
> > what I thought was the subject.
> >
> > Which kind of rims provide better caliper braking, constant or varying width?
>
> your phrasing implies you already have an answer carl.
>
> two factors: amplitude of any difference length of any difference
>
> an amplitude example is a "low spot" such as a wear indicator drilling. it's on a very small scale
> compared to the brake pad and makes no detectable difference.
>
> but if that were now a "high spot", suddenly you'd have wheel lock.
>
> similarly, if the low spot is now large relative to the pad size, that becomes noticeable too.
> going into the low spot is ok, but coming out again is the issue.
>
> > How much better? That is, at what point does varying rim width become noticeable when braking?
>
> a good question and i don't have an immediate quantitative answer for you. but we've all
> experienced this in a qualitative way whether it be on a bike with a lumpy rim or a car with a
> warped rotor. other than a bike with an old style rim, the only other application i can think of
> where braking surfaces do /not/ rely on precision machined surfaces are old railroad brakes. but
> r/r wheels sometimes develop flat spots and so these types of brakes suffer the same lockup
> problems as bikes.
>
> >
> > How much material is actually removed from machined rims compared to how much is left? Do
> > manufacturers compensate by making such rims thicker before machining, just as toilets are made
> > oversize to compensate for the way that they shrink in the kilns? (Sorry, but comparing rims to
> > toilets was irresistible.)
>
> good and somehow appropriate example. can't say how much gets machined off in practice, but if you
> had a variance of say +/- 0.1mm, you'd have to machine off at least 0.2mm to ensure uniformity.
> and of course, you'd make sure the unmachined component had correspondingly sufficient material to
> allow this.
>
> >
> > Does anodizing significantly weaken aluminum parts like rims, handlebars, and so forth? How?
>
> assuming that anodizing is the /only/ variable, it makes no difference to static strength but it
> does to fatigue. it's the relevance that is debatable. if you have a rim whose braking surfaces
> wears through in say 25,000 miles, how relevant is it that anodizing may reduce fatigue life from
> 50,000 miles to 45,000 miles?
>
> >
> > How does anodizing affect braking, regardless of how the width of the rim varies?
>
> no figures, but my experience is that hard anodized braking surfaces are better in the wet because
> the pads pick up less grit and therefore continue to be more effective.
>
> >
> > Curiously,
> >
> > Carl Fogel

Dear Jim,

It's interesting to a layman how differently you and Jobst Brandt answer these questions. Neither of
you can resist a quick dig, but then you both promptly settle down to what seem like good points
emphasizing different approaches.

It takes a layman a while to ponder them.

I take it that you expect brake pads coming out of a narrow enough rim section to cause problems,
but how much widening is needed is an open question, that you expect anodizing to decrease fatigure
resistance, but that the rim would wear out from braking long before it failed from fatigue, and
that you expect better wet braking from anodized surfaces because they pick up less grit.

Thanks for your explanations.

Carl Fogel

jim beam <uce@ftc.gov> wrote in message news:<0L1Hb.2321$W67.1691@newssvr27.news.prodigy.com>...
> jim beam wrote:
>
> <snip>
>
> >> Does anodizing significantly weaken aluminum parts like rims, handlebars, and so forth? How?
> >
> >
> > assuming that anodizing is the /only/ variable, it makes no difference to static strength but it
> > does to fatigue. it's the relevance that is debatable. if you have a rim whose braking surfaces
> > wears through in say 25,000 miles, how relevant is it that anodizing may reduce fatigue life
> > from 50,000 miles to 45,000 miles?
> >
>
> sorry, forgot the "how". anodizing can decrease fatigue performance because if it cracks, those
> cracks act as stress concentrations. fatige can then initiate at those points.
>
> but conversely, anodizing can protect significantly agains wear and corrosion and that can enhance
> fatigue life.
>
> jb

Dear Jim,

A nice surprise--one more present in the very bottom of the stocking!

I suppose that someone must have mentioned the anti-wear protection of anodizing, but I'd certainly
lost sight of it while wading through all the posts.

Thanks for taking the trouble to point out what I'd utterly forgotten.

Carl Fogel

"David L. Johnson" <david.johnson@lehigh.edu> wrote in message news:<RbOdnQHfiKU-YHGiRVn-gw@comcast.com>...
> On Fri, 26 Dec 2003 10:28:35 +0000, Carl Fogel wrote:
>
> > Which kind of rims provide better caliper braking, constant or varying width? How much better?
> > That is, at what point does varying rim width become noticeable when braking?
> >
> You're not asking the right question. You assume that the machining of the rim is done to make the
> width more uniform. You also assume that the machining makes a uniform rim. But machined sidewalls
> only came about after rims were anodized. If a non-machined rim was so uneven, it would have been
> a very good idea to machine it smooth even before they were anodized.
>
> The rims are machined to scrape off the anodized surface from the braking flats, since anodizing
> on the flats ruins the braking performance.

Dear David,

You see the advantage of being clueless? Even when I ask the wrong question, I get
fascinating answers.

I may have missed it completely in the replies from Jobst Brandt and Jim Beam, but my impression is
that they were both talking about anodized braking surfaces.

Jobst seemed to be saying that they act as insulators, overheat the brake pads, and don't brake as
well as unanodized braking surfaces anyway.

Jim seemed to be saying that they pick up less grit and therefore work better when wet.

(Both of them may have been led astray trying to deal with my ignorant questions, somewhat like the
Dilbert cartoon about who would win if a giant moth fought a giant bumblee wearing a wool suit.)

Now you're saying that rims are machined more to remove the anodizing from the braking surface than
to true them up?

If so, then Jobst's point about anodizing acting as insulation might still work to the extent that
the still-anodized middle of the rim won't dissipate heat as well as an unanodized rim.

But Jim's point about picking up less grit would seem to be implausible.

Of course, you might be mistaken (no offense is intended, since after all we're now asking if Jobst
and Jim were wrong by omission about this point).

Or you might be right about some rims and mistaken about others (some manufacturers might anodize
and then machine the braking surfaces, while others might machine and then anodize).

Or maybe you're mistaken to start with (the braking surface is anodized), but end up correct (the
thin anodized layer is soon worn off).

See why I love these simple questions? If I blink, one of you guys comes up with a whole new take on
something as simple as a metal hoop.

Thanks for raising a fascinating issue.

Carl Fogel

"BaCardi" <usenet-forum@cyclingforums.com> wrote in message
news:WVaHb.17892$hu3.16502@fe08.priv...enetserver.com...
> David L. Johnso wrote:
> > The rims are machined to scrape off the anodized surface from the braking flats, since
> > anodizing on the flats ruins the braking performance.
> > --
> > David L. Johnson
>
>
>
>
> Your assumption is wrong. Machined rims can still be anodized after the machining. Machining is
> NOT intended for scraping off the anodization. It is meant for uniformity and to smooth out an
> otherwise uneven seam. Machined rims are much more smoooooth than the old unmachined and seamed
> rims. That is fact.

Welding and machining a seam may be a good thing, and IIRC, Weinmann was doing that 30 years ago on
the Concaves. But machining and anodizing the whole rim is entirely unnecessary and arguably bad for
the rim. Even in the dark days, a bad seam could be fixed with about one minute of filing. And the
rims only cost $10 or $15 a pop -- and not $60. -- Jay Beattie.

Better to buy the rim already machined, then to take a file to file down an uneven seam.

Carl Fogel writes:

> Or you might be right about some rims and mistaken about others (some manufacturers might anodize
> and then machine the braking surfaces, while others might machine and then anodize).

> Or maybe you're mistaken to start with (the braking surface is anodized), but end up correct (the
> thin anodized layer is soon worn off).

You might also consider that the manufacturer doesn't understand the process being used and why.
Returning to the original concept of plain unadulterated rims of which th MA-2 is a prime example.
These rims outlasted the new and improved ones in all respects other than an occasional mismatch of
the rim joint that was incidentally a beauty mark not a functional problem, braking being
unaffected by it.

When the first hard anodized rims appeared, they were re-makes of existing rims and, like the MA-40
failed rapidly from anodizing induced cracking. All this discussion of advantages of the multiple
enhancement features we have today is a great smoke screen over the subject.

> See why I love these simple questions? If I blink, one of you guys comes up with a whole new take
> on something as simple as a metal hoop.

You forgot where we started.

> Thanks for raising a fascinating issue.

I'm not fascinated.

Jobst Brandt jobst.brandt@stanfordalumni.org

Carl Fogel wrote:
>
> I suppose that someone must have mentioned the anti-wear protection of anodizing,

not that i've seen on this forum. all i see is a bunch of red herrings confusing anodizing with
ceramic coating, an entirely different process involving plasma spray, not electrolysis.

jim beam <uce@ftc.gov> wrote in message news:<4ynHb.2647$ay.2210@newssvr27.news.prodigy.com>...
> Carl Fogel wrote:
> >
> > I suppose that someone must have mentioned the anti-wear protection of anodizing,
>
> not that i've seen on this forum. all i see is a bunch of red herrings confusing anodizing with
> ceramic coating, an entirely different process involving plasma spray, not electrolysis.

Dear Jim,

Perhaps I misunderstood, but I thought that Jobst indicated elsewhere in this thread that the thin
layer of anodized aluminum functions as an insulator, either as a ceramic or like a ceramic.

I hadn't thought of pretty metal as being the same as a beer mug, but if the metal adds molecules
and sort of fluffs up (see why I ask the questions around here instead of trying to answer them?),
then it seemed plausible that it would act as an insulator, making for hotter and less efficient
brake pads.

I take it that ceramic coating by plasma spray is an entirely different process. Does it suffer from
the same insulation problem?

Of course, I'm lost again. Going through this thread, I can't even tell which kind of rims (anodized
or plain) stop better when dry, much less what happens when wet--something that I thought would be
fairly cut-and-dried.

But I still think that the subject is fascinating, just as I think the nature of the responses is
fascinating. I do appreciate how you and Jobst are taking the time to grapple with these things. And
I'm still startled by how something as simple as a metal hoop can be so tricky.

Thanks again,

Carl Fogel

jobst.brandt@stanfordalumni.org wrote in message news:<eLmHb.5149$XF6.113219@typhoon.sonic.net>...
> Carl Fogel writes:
>
> > Or you might be right about some rims and mistaken about others (some manufacturers might
> > anodize and then machine the braking surfaces, while others might machine and then anodize).
>
> > Or maybe you're mistaken to start with (the braking surface is anodized), but end up correct
> > (the thin anodized layer is soon worn off).
>
> You might also consider that the manufacturer doesn't understand the process being used and why.
> Returning to the original concept of plain unadulterated rims of which th MA-2 is a prime example.
> These rims outlasted the new and improved ones in all respects other than an occasional mismatch
> of the rim joint that was incidentally a beauty mark not a functional problem, braking being
> unaffected by it.
>
> When the first hard anodized rims appeared, they were re-makes of existing rims and, like the MA-
> 40 failed rapidly from anodizing induced cracking. All this discussion of advantages of the
> multiple enhancement features we have today is a great smoke screen over the subject.
>
> > See why I love these simple questions? If I blink, one of you guys comes up with a whole new
> > take on something as simple as a metal hoop.
>
> You forgot where we started.
>
> > Thanks for raising a fascinating issue.
>
> I'm not fascinated.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org

Dear Jobst,

No, but you're awfully close to being pompous.

You might become fascinating by trying to put a number on how rapidly the MA-40 rims failed.
Elsewhere in this thread, Jim Beam suggested that rims wear out from braking in only 25,000
miles, but that the accelerated fatigue of anodizing-induced cracking might become a problem in
40,000 miles.

Or you might name the manufacturer and explain what part of which process you think that they don't
understand (anodizing, machining, fatigue, or whatever) rather than leaving us to guess.

Carl Fogel