Are anodized rims really stronger?
Menko Bernard Johnson
I don't know if someone has asked this before, but I have always been
told that rims that are hard anodized are stronger. I know they
are harder to stop with until you wear through the brake surface, but
is there an actual advantage to hard anodizing?
Menko
Bill Lloyd
Jobst Brandt
>> I don't know if someone has asked this before, but I have always been
>> told that rims that are hard anodized are stronger. I know they
>> are harder to stop with until you wear through the brake surface, but
>> is there an actual advantage to hard anodizing?
to which Bill Lloyd writes:
> uh-oh.
Yes it is true, this introduces an old subject that doesn't seem to make
anyone happy because the popular choice turns out no to be the good choice.
Anodizing colors the rims and if you like dark rims instead of shiny ones,
that's the good part. Just about everything else about anodized rims is
bad news. They cost more, brake more poorly, and most of all, they crack
and fail where aluminum rims never had problems before.
Anodizing is a hard and brittle porous crust that develops from the aluminum
in a suitable electro-chemical bath. Rims are made by extrusion in long
straight bars. These bars are anodized before they are curled into hoops
and in the curling process, the anodizing crazes with myriad micro surface
cracks. These remain benign unless the rim is sufficiently stressed.
In a tightly spoked wheel, the rim is under substantial compression (about
1000 lbf) and the cracks in the anodizing have no opportunity to open.
However, around the spoke sockets, the back side of the rim is under tension
and the cracks in the anodizing propagate into the metal causing whole
sections containing spoke sockets to break out. Bike shops that do much
wheel service have many examples of these.
Another mode of failure is that the rim splits circumferentially through
the braking surface and into the hollow of the rim. This leaves the tire
on the outer portion and the spokes on the inner. If you are lucky, the
two halves clunk along interlocked until you stop, as was the case with
the example I saw.
Embrittlement by anodizing is a well understood phenomenon in the aircraft
industry and there are many scientific papers under that heading that
quantify this process.
That braking is degraded by anodizing is often challenged by proponents
who point to the thin layer as being insignificant thermodynamically.
The reason this is not true is that the breaking energy is converted in
the softer material, the brake pad, and this heat must be dissipated in
the rim as a heat sink. This means that the instantaneous heat generated
in the face of the brake pad must transfer to the aluminum through the
insulation of the anodized ceramic coating. In the millisecond of exposure
the brake pad sees no deeper than the overcoat and as far as the heat
transfer is concerned, it might as well be solid ceramic.
How much longer must we put up with anodized rims? The fad must crumble
some day. Please!
Mitek Systems
>Menko
Read the FAQ. This has been discussed and argued interminably.
I believe the short answer is that anodizing makes them stronger on
the surface, but also makes them fail faster due to poorer heat
transfer during braking.
shane
j...@miteksys.com
Theodore Chen
>If the anodizing is kept thin and is colored, it has practically no effect
>on the durability of the frame.
am i right in thinking that when you say that the anodizing is colored,
you mean that it is so thin that it merely serves to change the appearance
of the surface? if not, and "colored" refers to a separate process,
how would the addition of coloring agents affect the durability of the
frame?
-teddy
Jobst Brandt
> My question is in regards to anodized aluminum frames. How well does
> the anodized surface wear and resist scratches and abrasions as compared
> to a painted frame? Does this embirttlement phenomenon, of anodizing,
> significantly affect the strength of the aluminum frame compared to one
> that is painted? Basically I am asking, what are the advantages and
> disadvantages of anodized frames opposed to painted frames?
Anodizing gives good protection and it is hard and is better attached to
the aluminum than most paint because it cannot be chipped off. That is,
unless you dig into the metal.
Anodizing doesn't weaken the metal, it only facilitates crack initiation
because it is a brittle and hard coating that crazes upon being stressed.
The places where frames usually crack from fatigue would be more likely
to crack, and do so earlier than a painted frame would.
If the anodizing is kept thin and is colored, it has practically no effect
on the durability of the frame. Vitus and Alan frames have had a thin
anodized treatment for years without ill effect. It is 'hard' anodizing,
that is as much as .001 or more thick that presents problems. Rims are
typically hard anodized. The anodizing is hard but it does nothing for
the metal.
Jobst Brandt
> am i right in thinking that when you say that the anodizing is colored,
> you mean that it is so thin that it merely serves to change the appearance
> of the surface? if not, and "colored" refers to a separate process,
> how would the addition of coloring agents affect the durability of the
> frame?
Hard anodizing is naturally dirty brown and lends itself only to being
colored in shades of dark brown to black/violet. The cosmetic anodizing
process is different, puts on a thinner coating and is used to make the
pastel colors often seen on aluminum bicycles and other hardware.
Harry Phinney
: if not, and "colored" refers to a separate process,
: how would the addition of coloring agents affect the durability of the
: frame?
The coloring is done in a separate process following the anodization,
but to the best of my knowledge the dies used have no significant affect
on the material properties of either the oxide layer or the underlying
Al alloy. Normal anodizing results in a relatively thin and porous
layer of oxide which can readily be died. The hard anodizing process
generates a much denser and generally thicker layer of oxide which, as
Jobst noted, will always result in dark colors.
Harry Phinney ha...@cv.hp.com
Michael Taffe
A
>
>Anodizing is a hard and brittle porous crust that develops from the aluminum
>in a suitable electro-chemical bath. Rims are made by extrusion in long
>straight bars. These bars are anodized before they are curled into hoops
>and in the curling process, the anodizing crazes with myriad micro surface
>cracks. These remain benign unless the rim is sufficiently stressed.
>
" With 5086 aluminum, the extrusions are cut to the proper
length and rolled into hoops. With 7075, the extrusion is formed
into a spiral long enough to make six or so rims. This is heat
treated, quenched and straightened immediately
afterward....(description of final forming of rim) ....The rims are
cleaned and polished by machine, artificially aged in the oven, then
anodized and surface-treated."
The above is a description of the Campy rim building process, Jobst.
Since they anodize after forming the rim, does this mean that campy
rims (and any others processed in this order) are free of your
claimed hard-anodizing bugaboos
I seem to remember from the last round of debates that perhaps it is
only particular brands of rims (Mavic?) that show these
problems--perhaps the failure is only related to the
post-anodization forming and not the process itself.
Finally, you say the micro cracking is benign unless the rim is
sufficiently stressed. What exactly constitutes sufficient stress?
500mi? 5000mi? 10000mi?
>
>How much longer must we put up with anodized rims? The fad must crumble
>some day. Please!
>jobst_...@hplabs.hp.com
"put up with" ?? Noone is forcing you to buy them...does the color
of the rim on someone else's bike offend?
mike
--
Mike Taffe * When the force of logic fails,
mta...@ucsd.edu * only the logic of force remains.
Jobst Brandt
> " With 5086 aluminum, the extrusions are cut to the proper
> length and rolled into hoops. With 7075, the extrusion is formed
> into a spiral long enough to make six or so rims. This is heat
> treated, quenched and straightened immediately
> afterward....(description of final forming of rim) ....The rims are
> cleaned and polished by machine, artificially aged in the oven, then
> anodized and surface-treated."
> The above is a description of the Campy rim building process, Jobst.
> Since they anodize after forming the rim, does this mean that Campy
> rims (and any others processed in this order) are free of your
> claimed hard-anodizing bugaboos
I don't know that this solves the problem but it helps. If the rims in
question have steel sockets riveted into them then there will be enough
crazing to nullify the advantage of anodizing last because, as is evident
on the braking surfaces, installing sockets bulges the rim. Steel cannot
be part of the rim in the anodizing process. Therefore, I assume these
rims are deep section aero rims without sockets.
> Finally, you say the micro cracking is benign unless the rim is
> sufficiently stressed. What exactly constitutes sufficient stress?
> 500mi? 5000mi? 10000mi?
I meant by that stress level, not number of stress cycles. I know of light
weight riders who have had such rims for many miles without cracking.
>> How much longer must we put up with anodized rims? The fad must crumble
>> some day. Please!
> "put up with" ?? Noone is forcing you to buy them...does the color
> of the rim on someone else's bike offend?
Oh yes, you walk into a bike shop and look what's in stock. Unless I
special order them, MA-2's are not part of the inventory at the shops
in my area, be that at noon or later. Who is this noone guy anyway?
Matt Bushore
For those without the resources, I might attempt to breifly explain
anodizing, to the best of my knowledge.
The aluminum part is placed into a sulferic acid bath, and connected
to a power source. Another electrode ( typically lead?) is place in the bath
as well. A fairly high current is passed though the solution, which etches
the aluminum slightly and makes it porus.
The acid bath is then rinsed off in distilled water and placed into
a hot dye bath. The dye is allowed to permeate into the pores for
some time, and then the part is moved to another bath ( nickel something)
where the pores are sealed closed with a clear topcoat.
There are many. many variations on anodizing Al, and many many
organic dyes that are usable, however, consisent results require
a closely monitored setup.
If any of this is wrong, laugh at me to yourself, then correct me.
No use spreading misinformation.
--
Matt Bushore
--
Matt Bushore
Eric Topp
: Michael Taffe writes:
[snip]
: >> How much longer must we put up with anodized rims? The fad must crumble
: >> some day. Please!
:
: > "put up with" ?? Noone is forcing you to buy them...does the color
: > of the rim on someone else's bike offend?
:
: Oh yes, you walk into a bike shop and look what's in stock. Unless I
: special order them, MA-2's are not part of the inventory at the shops
: in my area, be that at noon or later. Who is this noone guy anyway?
Try Wheelsmith--they stock them.
-=E
Richard Foulk
>WS if they had MA-2 rims. All times they told me they had none and that
>MA-2 rims were nearly impossible to find due to "inventory problems"
>Mavic's American distributor was having. They suggested the MA40 rims,
>but I didn't want to buy hard anodized rims. I finally decided to build
>up my wheels with the slightly heavier Mod3's, and even these took a
>couple weeks to special order.
I've had better luck with Sun rims. They have a wider selection
and better availability. Plus they make lighter rims than Mavic, that
hold up quite well.
--
Richard Foulk ric...@pegasus.com
Eric House
Kellagher) wrote:
> In article 8...@enterprise.rdd.lmsc.lockheed.com, bushnell@aml_19.rdd.lmsc.lockheed.com (Bill Bushnell) writes:
>
> >Do others have difficulty obtaining Mavic's lower-priced rims such
> >as the MA-2's, and unadorned Mod3's and Mod4's?
>
> I've always gotten my MA-2's from Excel in Boulder.
Like an earlier poster, I get my MA-2s from Wheelsmith, though they
don't tend to stock the 36-hole model. And forget about special-ordering
anything from those guys! Last time I tried this it was 2 weeks before
they bothered to place the order.
But interestingly, Excel now has the *highest* price I know of on MA-2
rims: $30. Most local shops, including Wheelsmith, are in the $25 range.
Colorado Cyclist appears not to intend to carry them any more, as they
blew out their remaining stock a few months back and I don't see them in
their latest catalog.
--Eric "where's my .sig?" House
Harry Phinney
: In the spring of '92 I built up
: a set of wheels with Campy Ypsilon, non aero, silver finish rims.
: ...
: I had to fiddle with it constantly; needed retruing at least once
: a week.
As they say, your mileage may vary. I've used both the Ypsilon box and
Omega box rims with very good results. I find them to be equivalent in
quality to Mavic's products, and so far none of the Campy rims have
cracked around the ferrules, while I've had multiple MA-40s fail in this
manner.
Harry Phinney ha...@cv.hp.com
Peter Lancaster
stripped of paint, might look great with an anodized finish. It's time for a paint job...
peter lancaster peterl@microsoft