carlfogel@comcast.net (Carl Fogel) writes:

> Tim McNamara <timmcn@bitstream.net> wrote in message news:<m2fzf47aar.fsf@Stella-Blue.local>...
>
> [snip Carl Fogel and David Johnson and get to the weird wear]
>
> > Basically machining compensates for several problems caused or worsened by anodizing: poor wet
> > braking performance, brake squeal, rapid brake pad wear, and ugliness when the anodizing starts
> > to be worn off by the brakes. You'll also see an interesting pattern of wear, which is shiny
> > patches of almost completely bare aluminum coinciding with the spokes, and patches of partial
> > wear coinciding with the spaces bewtwwen the spokes. Machining removes all these problems by
> > removing the anodizing from the braking surface.
>
> You're saying that anodized wheel rims eventually show worn-off patches on the braking surface
> next to the spokes?

Seen it many times.

> Maybe you guys know about all this, but I'm flabbergasted.
>
> What causes this? Are the worn patches on each side of the rim and next to each spoke, 32 on the
> left and 32 on the right?

Yes. Cause? I've assumed (not necessarily correctly) that the spoke tension causes the sidewalls to
bulge very slightly (on the order of .0001") at each spoke. OTOH I suppose that the process of
piercing the rim for the spoke holes could also cause some local deformation.

> Or are they staggered, 16 on one side and 16 on the other, reflecting where the spokes pull to one
> side and then to the other?

No.

> Do non-anodized rims wear in the same fashion, but fail to show it to the naked eye because it's
> all the same color and finish?

Good question, I assume this is the case.

> If the wheels wear regularly deeper next to the spokes (either staggered or symetrically), how the
> hell do people true worn wheels? Is this wear, fascinating as I find it, actually inconsequential
> in terms of depth?

Think about it- what wears first? High spots. So the brakes essentially machine the rim sidewalls
flat initially. And I suspect we're talking about high spots that are .0001" higher than the low
spots. Eventually, given enough time and braking especially in the rain or mud, the braking surface
will be worn thin enough to fail from the stress caused by tire inflation pressure.

> For a simple hoop, the bicycle rim is certainly giving me my money's worth in surprises.

A bicycle wheel is a dynamic structure, not a simple hoop. I've been participating in this newsgroup
for 10 years, have read Jobst's book cover to cover several times, and I still learn new stuff about
wheels that I hadn't comprehended.

Oh yeah, no doubt!

It's more, yes, but $40 more is quite an exagerration.

> You're saying that anodized wheel rims eventually show worn-off patches on the braking surface
> next to the spokes?
>
> Maybe you guys know about all this, but I'm flabbergasted.
>
> What causes this? Are the worn patches on each side of the rim and next to each spoke, 32 on the
> left and 32 on the right? Or are they staggered, 16 on one side and 16 on the other, reflecting
> where the spokes pull to one side and then to the other?

i blame it on the rim being distorted by spoke tension, esp so w/ sockets. as the rim is pulled
inward at the spokes, the walls budge outward. the brake pads bluff the wide spots first. i refer
to it as "strobing" and consider it to be a sign of a well built wheel, high enuff tension to
distort the rim tho you can only really see it on a dark coated rims.

bc_cletta@yahoo.com (B.C. Cletta) wrote in message news:<add863d6.0312290755.4b53194d@posting.google.com>...

[snip]

Dear Tim and BC,

If the worn patches on the braking surface that you've noticed on anodized rims are on sides and
opposite every spoke, then it seems unlikely that any sideways distortion from the dished spokes is
involved. That would produce worn patches alternating from side to side, and I would have loved it--
what a shame.

Spoke tension might be involved, as you both suggest, but it also seems unlikely because a spoke
pulling on the bottom of a roughly V or U shaped rim should cause the bottom to deepen and pull the
tops of the V or U together, not open them. (I think--a hoop with a V-shaped rim may behave
differently than a simple two-dimensional V.)

So maybe the explanation is Tim's alternate theory about the rim being very slightly bulged outward
around the spoke-holes by whatever process is used to make holes in the rim?

Carl Fogel

jim beam:

> lies come from;
>
> "experts" that know nothing of the dynamic properties of carbon composites but feel qualified to
> postulate their vibration transmission inferiority.

Add to that "experts" who claim the opposite, but fail to show any supporting scientific data
whatsoever.
>
> "experts" that know nothing of work hardening differentials between mild and stainless steels,
> their deformation & fatigue mechanisms but feel free to postulate radical theories of fatigue
> elimination that would turn the entire materials world on its head.

Add to that "experts" who claim the opposite, but fail to show any supporting scientific data
whatsoever.

> "experts" that consider their materials knowledge superior to an entire industry of rim
> manufacturers that dare to protect their product by anodizing, manufacturers that dump millions
> into research. all because this "expert" reads a little about one of /many/ different possible
> failure modes but feels by some strange intuition that the story stops there, further research is
> irrelevant and that they are now suddenly qualified to apply this small subset of convenience to
> all failures they see.

Add to that "experts" who claim the opposite, but fail to show any supporting scientific data
whatsoever.

> "Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if
> nothing had happened. -- Winston Churchill"
>
>
> happy holidays.

jim beam <uce@ftc.gov> wrote in message news:<7DFHb.2956$rd1.2698@newssvr25.news.prodigy.com>...
> Carl Fogel wrote:
> > jim beam <uce@ftc.gov> wrote in message news:<4ynHb.2647$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.
>
> swallowed a red herring.
>
> yes, aluminum oxide is technically a ceramic, but it is not /the/ ceramic used in the rim coating
> sense. also, aluminum oxides are not necessarily bad thermal conductors. nor are 6061 aluminum
> alloys good thermal conductors.
>
> >
> > 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.
>
> not necessarily relevant. there is extensive research on ceramics being used in high performance
> brake systems, both disks & pads.
>
> http://www.uni-stuttgart.de/IFKB/en/research/17-e.pdf shows disks.
>
> >
> > I take it that ceramic coating by plasma spray is an entirely different process.
>
> entirely different.
>
> scroll to the bottom of this page for a schematic
>
> http://www.gordonengland.co.uk/tsc.htm
>
>
> > Does it suffer from the same insulation problem?
>
> depends on the ceramic. to be fair, mavic /do/ list thermal insulation as one of their reasons for
> use, but as you will see from a little research, alumina & titania can be excellent thermal
> conductors.
>
> > 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.
>
> the proof of the pudding is in the eating. my experience of ceramic & cd rims is entirely
> favorable - and no comparision to a badly fouled pad full of metal scrapings.
>
> >
> > But I still think that the subject is fascinating,
>
> fascinating indeed! that's why i got into materials.
>
> > 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

Dear Jim and Jobst,

I like the http://www.gordonengland.co.uk/tsc.htm page, which panders to my love of interesting
drawings and lists of good and bad qualities.

At this point, I have to admit that I'm not even sure what kind of rims are being debated, so pardon
an embarrassingly dumb question.

There are plain aluminum rims.

There may be machined plain aluminum rims.

There may be anodized rims that were later machined so that they have plain braking surfaces--bikini
lines in their tans, so to speak.

There may be plain machined rims that have later been anodized all over--nude sunbathers with no
plain strips lacking anodization.

There are probably plasma-sprayed rims with some kind of ceramic brake-surface coating. (Do cd and
ceramic mean the same thing?)

Is this roughly the field of contestants?

If so, how long do anodized or plasma-sprayed surfaces stand up to braking wear, leaving plain
aluminum exposed?

And which ones in good condition will stop in the shortest distance when dry or wet?

(Given how tricky things seem to be, I understand that these questions may be harder to answer than
a hopeful layman would like to think.)

Thanks again,

Carl Fogel

Mark writes-<< That's your take on it. My take is, save me $40 per rim and hand me the
> file for 3-5 minutes work. Mark (I buy the silver rims when I can find 'em cheap) >><BR><BR>

Torelli Experts with a non welded seam are $30, OpenPros are $60, Not $40 but it isn't an
exaggeration either.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

carlfogel@comcast.net (Carl Fogel) wrote in message news:<8bbde8fc.0312291824.77d90eda@posting.google.com>...
> bc_cletta@yahoo.com (B.C. Cletta) wrote in message
> news:<add863d6.0312290755.4b53194d@posting.google.com>...
>
> [snip]
>
> Dear Tim and BC,
>
> If the worn patches on the braking surface that you've noticed on anodized rims are on sides and
> opposite every spoke, then it seems unlikely that any sideways distortion from the dished spokes
> is involved. That would produce worn patches alternating from side to side, and I would have loved
> it--what a shame.
>
> Spoke tension might be involved, as you both suggest, but it also seems unlikely because a spoke
> pulling on the bottom of a roughly V or U shaped rim should cause the bottom to deepen and pull
> the tops of the V or U together, not open them. (I think--a hoop with a V-shaped rim may behave
> differently than a simple two-dimensional V.)
>
> So maybe the explanation is Tim's alternate theory about the rim being very slightly bulged
> outward around the spoke-holes by whatever process is used to make holes in the rim?
>
> Carl Fogel

This question could be easily answered with a good micrometer and an unbuilt, unmachined wheel.

JP

Two different rims. Not even close to a good comparison.

Carl Fogel wrote:
> Dear Jim and Jobst,
>
> I like the http://www.gordonengland.co.uk/tsc.htm page, which panders to my love of interesting
> drawings and lists of good and bad qualities.
>
> At this point, I have to admit that I'm not even sure what kind of rims are being debated, so
> pardon an embarrassingly dumb question.
>
> There are plain aluminum rims.

yes

>
> There may be machined plain aluminum rims.

yes, but not many.

>
> There may be anodized rims that were later machined so that they have plain braking surfaces--
> bikini lines in their tans, so to speak.

yes, anodized then machined. the majority of the current market.

>
> There may be plain machined rims that have later been anodized all over--nude sunbathers with no
> plain strips lacking anodization.

yes. mavic "cd" for example.

>
> There are probably plasma-sprayed rims with some kind of ceramic brake-surface coating.

yes. mavic "ceramic" for example.

> (Do cd and ceramic mean the same thing?)

no. "cd" is hard anodizing [distinct from "regular" anodizing]. ceramic is the plasma spray
coated stuff.

>
> Is this roughly the field of contestants?

there's also anodized unmachined like [versions of] mavic ma2, ma40 [sic] and cxp14, but they're not
made any more, so you pretty much have it covered.

>
> If so, how long do anodized or plasma-sprayed surfaces stand up to braking wear, leaving plain
> aluminum exposed?

don't have figures for you, but it would be easy enough to measure relative wear rates. anecdotally,
one my friends has been riding a pair of ceramic rims [spox wheels] on their mountain bike for over
3 years. apart from the fact that he's chipped the surface in a few places, they are perfect and the
coating shows no signs of wearing through. this is with annual milage of about 3,000 strictly off
road. imo, that's impressive for the conditions where we ride.

before i converted to disk, i was running one plain anodized and one cd rim on my mtb. the wear rate
on the plain was fast and it was close to failure in about a year. there's no way it would have
lasted 9,000. the cd was substantially better than the plain. it started to lose some of its coating
on the braking surface after a few months, but it was still holding up well and braking was great.
obviously, once the coating had worn off completely, it would have then followed the wear path of
the plain rim.

>
> And which ones in good condition will stop in the shortest distance when dry or wet?

don't have figures for you although it would be easy to measure with a dynamometer.

my experience is that they are all good in the dry, with plain rims having a /slight/ advantage over
cd when new. but it's the wet that's the real differentiator. with standard shimano or campy brake
blocks, my experience is that plain rims work well in the wet until they grit up
- when performance definitely drops off. cd's work great in the wet and keep working better longer
because they do not fill the pad with metal scrapings as quickly. they're not immune to the grit
effect, but relative to plain, they're a big improvement.

my experience of ceramics is loaner wheels. they were good in the dry and great in the wet. no
evidence of gritting whatsoever - i was impressed. if i habitually commuted in the rain, i'd
definitely buy my own now. and i will when it comes time to replace.

mavic publish a bunch of favorable ceramic braking stats, but they're in percentage form so it's
impossible to judge their absolute efficacy. otoh, percentages are sensible being as they are
relative to the other condition variables, tires, surface conditions, etc.

>
> (Given how tricky things seem to be, I understand that these questions may be harder to answer
> than a hopeful layman would like to think.)
>
> Thanks again,
>
> Carl Fogel

SocSecTrainWreck@earthlink.net (JP) wrote in message news:<1f323b67.0312300513.3b6a9693@posting.google.com>...
> carlfogel@comcast.net (Carl Fogel) wrote in message
> news:<8bbde8fc.0312291824.77d90eda@posting.google.com>...
> > bc_cletta@yahoo.com (B.C. Cletta) wrote in message
> > news:<add863d6.0312290755.4b53194d@posting.google.com>...
> >
> > [snip]
> >
> > Dear Tim and BC,
> >
> > If the worn patches on the braking surface that you've noticed on anodized rims are on sides and
> > opposite every spoke, then it seems unlikely that any sideways distortion from the dished spokes
> > is involved. That would produce worn patches alternating from side to side, and I would have
> > loved it--what a shame.
> >
> > Spoke tension might be involved, as you both suggest, but it also seems unlikely because a spoke
> > pulling on the bottom of a roughly V or U shaped rim should cause the bottom to deepen and pull
> > the tops of the V or U together, not open them. (I think--a hoop with a V-shaped rim may behave
> > differently than a simple two-dimensional V.)
> >
> > So maybe the explanation is Tim's alternate theory about the rim being very slightly bulged
> > outward around the spoke-holes by whatever process is used to make holes in the rim?
> >
> > Carl Fogel
>
> This question could be easily answered with a good micrometer and an unbuilt, unmachined wheel.
>
> JP

Dear JP,

Well, yes, but the drawback to your theory is that I'd have to be smart enough to think of
doing that.

Now that you've done the thinking for me (thanks), I'll see if my local bike shop has an unmachined
rim that they'll let out on a chaperoned date with my dial calipers.

But before I start measuring, an even easier test belatedly occurs to me.

Has anyone noticed an extra wear spot by the valve stem on anodized rims worn into faint strobe
patterns? If so, then the process of putting holes in the rim is likely to be the culprit
responsible for the tiny bulges that wear off sooner under braking.

Carl Fogel

"Carl Fogel" <carlfogel@comcast.net> wrote in message
news:8bbde8fc.0312301238.179f3223@posting.google.com...

<snip>

: Has anyone noticed an extra wear spot by the valve stem on anodized rims worn into faint strobe
: patterns? If so, then the process of putting holes in the rim is likely to be the culprit
: responsible for the tiny bulges that wear off sooner under braking.
:
: Carl Fogel

Yes, my old Open 4 CD has those wear spots (one on each side) at the valve stem as well as at
every spoke.

--
Please remove the under_scores if sending me mail.

Carl Fogel writes:

> Has anyone noticed an extra wear spot by the valve stem on anodized rims worn into faint strobe
> patterns? If so, then the process of putting holes in the rim is likely to be the culprit
> responsible for the tiny bulges that wear off sooner under braking.

The stem hole, if socketed, is the weakest cross section on most rims. The rim will bulge there at
least as much as spoke locations since it is the compression on the rim that makes these
deformations.

Jobst Brandt jobst.brandt@stanfordalumni.org

jobst.brandt@stanfordalumni.org wrote in message news:<AOnIb.5483$XF6.125264@typhoon.sonic.net>...
> Carl Fogel writes:
>
> > Has anyone noticed an extra wear spot by the valve stem on anodized rims worn into faint strobe
> > patterns? If so, then the process of putting holes in the rim is likely to be the culprit
> > responsible for the tiny bulges that wear off sooner under braking.
>
> The stem hole, if socketed, is the weakest cross section on most rims. The rim will bulge there at
> least as much as spoke locations since it is the compression on the rim that makes these
> deformations.
>
> Jobst Brandt jobst.brandt@stanfordalumni.org

Dear Jobst,

Aha! Another explanation that utterly escaped me. So it's the compression between holes so to speak,
bulging at weak points.

Thanks,

Carl Fogel