Hard anodized rims-good or bad?
Mike Krueger
Manufacturers offer identical rims with one model being polished or anodized in
a color bath, vs. a similar model being hard anodized (for example, Mavic CD).
The hard anodized version is always more expensive. Although manufacturer say
this makes the rim stronger, others here have said the opposite is true. I have
seen hard anodized rims crack, but have less experience with plain silver rims.
All else being equal, are hard anodized rims worth the extra $ or should they
be avoided?
terry morse
> All else being equal, are hard anodized rims worth the extra $ or should they
> be avoided?
Avoided. Hard anodizing a piece of metal that undergoes stress is a
first year engineering mistake. It's a failure waiting to happen.
--
terry morse
Palo Alto, CA
http://www.terrymorse.com/bike/
Dave Blake
> All else being equal, are hard anodized rims worth the extra
> $ or should they be avoided?
Avoided. The anodization wears off raipdly. Riding in the rain
will lead to very poor braking as the hard anno wears off on
the brake pads.
There has NEVER been a demonstration of a positive effect of
hard anno on rim longevity or durability in practice. Existing
evidence suggests the opposite.
--
Dave Blake
dbl...@phy.ucsf.edu
Trevor Jeffrey
>this makes the rim stronger, others here have said the opposite is true. I
>have
a marginally higher load before buckling. Save the cash, use a wider rim if
more strength is required. Hard anodising does contribute to crack formation
as does any relatively hard coating. The only effect I have noticed is a
crazing on the visible flat part of the rim on a MA40 Oh and they're a pain
braking, until the anodizing has worn through.
--
Trevor M Jeffrey
Eat your greens before email.
------
Tho X. Bui
Even if all else not being equal, avoid hard anodizing. On some
aluminum alloys, hard anodizing can reduce the fatige strength by as
much as 50%. Being a cheap skate, I seldom turn away things. I would
not, however, use hard anodized rims to build a wheel even if it's free.
Tho
Matthew Temple
I converted the bike they were on to nine speeds.) Those wheels were
from a 1970's TREK Elance 400. They must have 20,000 miles on them
Hard anodized. Used in and around Boston and other parts of New
Enmgland where the roads, to be kind, suck. I suspect this is
one of those issues where the "weakening" comes into play only
under certain peculiar situations. That being said, since the
anodized part wears away on the rim surface after a short while,
why is it considered an a good thing for a wheels rim to be
hard-anodized?
Matt
--
================================================================
Matthew Temple Tel: 617/632-2597
Director, Research Computing Fax: 617/632-4814
Dana-Farber Cancer Institute m...@research.dfci.harvard.edu
44 Binney Street, SM 339 http://research.dfci.harvard.edu
Boston, MA 02115 Choice is the Choice!
Qui si parla Campagnolo
Manufacturers offer identical rims with one model being polished or anodized in
a color bath, vs. a similar model being hard anodized (for example, Mavic CD).
The hard anodized version is always more expensive. Although manufacturer say
this makes the rim stronger, others here have said the opposite is true. >>
Particularly with eyelets, I would always opt for a non-hard anodized rim..It
does nothing to improve rim performance or longevity and can lead to premature
cracking around the nipple holes..
Not worth the $ and I wouldn't use them even if they were the same price.
Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl ST.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
Qui si parla Campagnolo
sustain
a marginally higher load before buckling. >>
Sorry, does not make the aluminum of the rim any stiffer to reduce buckling..
alex wetmore
<3BD38FD8...@research.dfci.harvard.edu>:
>I've got a pair of Matrix wheels (I just retired them last month when
>I converted the bike they were on to nine speeds.) Those wheels were
>from a 1970's TREK Elance 400.
Where did you find a 1970s Trek Elance 400? This is a bike that didn't
exist until the early to mid 1980s.
>They must have 20,000 miles on them
>Hard anodized. Used in and around Boston and other parts of New
>Enmgland where the roads, to be kind, suck. I suspect this is
>one of those issues where the "weakening" comes into play only
>under certain peculiar situations.
Hard anodized rims usually have surface cracks near the spoke holes.
Eventually these grow and the spokes pull through. It has happened to every
HA rim that I've owned, except for one that taco'd earlier due to a stupid
mistake on my part (didn't tighten the QR hard enough on a bike with low
gearing and a horizontal dropout, and the wheel pulled out, jammed in the
chainstays, and taco'd).
alex
John Carrier
H/A rims are prone to failure, I've had a pair of the old Mavic Open 4CD's
and a pair of Campy Hardox rims that were heroic and their strength and
resistance to abuse ... lasted for many seasons.
R / John
Bluto
>
> Sorry, does not make the aluminum of the rim any stiffer to reduce buckling..
I would not be so hasty to assert this unless you have data to support
your claim. From what I know about electro-anodizing (and I have done
some myself), the effect of hard anodizing is to turn the surface
layer of the metal into a ceramic-impregnated metal matrix composite.
This layer would be stiffer by some amount than the base material;
increased stiffness is a property of MMCs.
_How much_ stiffer is an open question. Whether there are associated
drawbacks or whether there is a net benefit to using hard ano rims is
also up for dispute. (I prefer bare aluminum rims for their toughness
and ductility.) But I see no reason to think that hard anodizing has
no stiffening effect on rims.
Chalo Colina
Tim McNamara
Temple <m...@research.dfci.harvard.edu> wrote:
> I've got a pair of Matrix wheels (I just retired them last month when
> I converted the bike they were on to nine speeds.) Those wheels were
> from a 1970's TREK Elance 400. They must have 20,000 miles on them
> Hard anodized. Used in and around Boston and other parts of New
> Enmgland where the roads, to be kind, suck. I suspect this is
> one of those issues where the "weakening" comes into play only
> under certain peculiar situations.
Not all that peculiar. Compare two identical rims, the Mavic MA2 and
the MA40. Same extrusion, same material, same sockets, etc. The only
difference is that the MA40 is anodized and the MA2 is polished bare
aluminum. The MA40 has a well-known reputation for cracking around the
spoke eyelets, whereas this is not a problem with the MA2.
I have personally cracked 6 or so anodized rear rims from Mavic, Sun,
Fir, etc. Several cracked in under 1000 miles, all in under 5,000
miles. It has been quite dramatic on a couple of occasions with the
spoke ripping out of the rim with a loud crack. I have never cracked a
polished aluminum rim despite putting more miles on them (7,000 on one
wheelset built with MA2's, also Rigida 13-19s, Sun CR 16a's etc. Even
the non-socketed polished aluminum rims hold up better than the
anodized ones with sockets).
The issue is how cracks form in the anodized surface layer, which is
much more brittle than the underlying aluminum, and then propogate
through the aluminum. You can actually see the microfractures around
the spoke holes on silver anodized rims by reflecting light obliquely
off the surface. They will eventually propogate into cracks and cause
rim failure.
> That being said, since the anodized part wears away on the rim
> surface after a short while, why is it considered an a good thing for
> a wheels rim to be hard-anodized?
Because the bike-buying public has been hoodwinked by marketing flacks
into believing that (1) anodized rims are stronger, (2) that anodizing
and heat treating are the same thing, (3) that anodized rims are
"cooler." It's *not* a good thing for rims to be anodized, but such
mundane mechanical considerations are beneath the "designers" at most
bike companies. They now sell fashion, not bikes. If they were
selling bikes, we'd mostly all be riding British-style three speeds and
Alex Singer-style randoneuses. Rivendell would be the size of Trek.
Tom Ace
I don't regard this as an open question.
Jobst Brandt investigated the relative stiffness of Mavic MA-2 and MA-40
rims, which were extruded from the same die and differed only in the
absence and presence of hard anodization (respectively). He hung
weights from both (unlaced) rims and measured their deflection.
The results agreed with theory: anodizing did not improve stiffness.
Jobst reported this here in rec.bicycles.tech. You can find
his article with google.com; the header reads:
From: jbr...@hpl.hp.com (Jobst Brandt )
Subject: Re: Problems with Mavic SUP rims?
Date: 1996/08/22
Message-ID: <4vgbet$k...@hplms2.hpl.hp.com>#1/1
Just say no to hard anodization on rims.
Tom Ace
TBGibb
>That being said, since the
>anodized part wears away on the rim surface after a short while,
>why is it considered an a good thing for a wheels rim to be
>hard-anodized?
It looks COOL until you use your brakes.
Tom Gibb <TBG...@aol.com>
kwalters
Tim McNamara wrote:
> Not all that peculiar. Compare two identical rims, the Mavic MA2 and
> the MA40. Same extrusion, same material, same sockets, etc. The only
> difference is that the MA40 is anodized and the MA2 is polished bare
> aluminum. The MA40 has a well-known reputation for cracking around the
> spoke eyelets, whereas this is not a problem with the MA2.
>
I have a 36 hole MA2 rear wheel with ~8K miles on it. Six of the eyelets
have cracks. But then, I weigh 200 lbs.
Ken
Peter Cole
news:8b4b7de4.0110...@posting.google.com...
> vecc...@aol.com (Qui si parla Campagnolo) wrote :
> >
> > Sorry, does not make the aluminum of the rim any stiffer to reduce
buckling..
>
> I would not be so hasty to assert this unless you have data to support
> your claim. From what I know about electro-anodizing (and I have done
> some myself), the effect of hard anodizing is to turn the surface
> layer of the metal into a ceramic-impregnated metal matrix composite.
> This layer would be stiffer by some amount than the base material;
> increased stiffness is a property of MMCs.
This is wrong. Anodizing simply grows a layer of aluminum oxide on the
surface. Hard anodizing (or hardcoating) is just a thicker layer (>.001").
Aluminum oxide is extremely hard, brittle, and due to its molecular
arangement (hexagonal) microporous, which enables it to be colored.
> _How much_ stiffer is an open question. Whether there are associated
> drawbacks or whether there is a net benefit to using hard ano rims is
> also up for dispute. (I prefer bare aluminum rims for their toughness
> and ductility.) But I see no reason to think that hard anodizing has
> no stiffening effect on rims.
I don't have numbers, but intuitively stiffness improvement seems a real
reach given the relative cross sections of the rim and the anodized layer.
In all of the literature I have seen there are ample references to the
improved wear resistance (frictional), and corrosion resistance of anodized
parts, no claims of improved stiffness or strength are made. Significant
(50%) loss of fatigue resistance is frequently mentioned.
Qui si parla Campagnolo
support
your claim >>
<< the effect of hard anodizing is to turn the surface
layer of the metal into a ceramic- >>
That surface being stiffer is microns thick(or thin) and will not prevent
'buckling' as mentioned by the other poster...
Mike Krueger
> The issue is how cracks form in the anodized surface layer, which is
> much more brittle than the underlying aluminum, and then propogate
> through the aluminum. You can actually see the microfractures around
> the spoke holes on silver anodized rims by reflecting light obliquely
> off the surface. They will eventually propogate into cracks and cause
> rim failure.
Weren't we making a distinction between colored anodizing (i.e. Mavic
Reflex silver, blue) vs. hard anodizing (Mavic CD)? The clear
consensus is that hard anodizing is n.g., but now what about colored
anodizing? It's chemically a different process, right?
I posted the original question, because I'm looking for a decent
box-shaped tubular rim with double eyelets. So who still makes such a
rim in basic polished aluminum?
terry morse
How many miles per season?
Joshua_Putnam
>> > Sorry, does not make the aluminum of the rim any stiffer to reduce buckling..
>> I would not be so hasty to assert this unless you have data to support
>> your claim.
>I don't regard this as an open question.
>Jobst Brandt investigated the relative stiffness of Mavic MA-2 and MA-40
>rims, which were extruded from the same die and differed only in the
>absence and presence of hard anodization (respectively). He hung
>weights from both (unlaced) rims and measured their deflection.
>The results agreed with theory: anodizing did not improve stiffness.
For waht it's worth, the results also agree with Mavic's OEM rim
catalog of the same year, which made absolutely no claims about
HA rims being stronger or stiffer, and showed no difference in
their specifications for rim strength between HA and plain
versions of the same rims.
--
jo...@nw.incc.net is Joshua Putnam
http://www.phred.org/~josh/
(formerly jo...@wolfenet.com)
Jon Isaacs
>box-shaped tubular rim with double eyelets. So who still makes such a
>rim in basic polished aluminum?
>
>
Torelli still makes a basic box rim in polished aluminum. They also use
stainless steel eyelets.
The Expert and the Master both look like good rims. I had one on the rear for
quite a while until I hit a nice pothole at 40 mph one evening.
I believe someone mentioned that Ambrosio actually makes their rims.
Their website is:
http://www.torelli.com/parts/wheels.html
jon isaacs
Tom Kunich
news:3BD508E1...@frii.com...
One of the failure modes of a rim is to get cracks around the spoke
holes. Hard anodized rims generally get these cracks in a far shorter
time than polished rims.
One of the problems is that most people think of rims as all the same
but they are not. As the aluminum extrusions are made it wears away the
tool. When the tool is worn beyond a certain point it is replaced with a
new tool that might be slightly different than the previous one was when
new.
The upshot of this is that two rims are seldom the same weight or have
the same thickness of metal around the spoke holes or on the braking
surfaces. This can lead to some very light rims coming from an
undersized tool newly installed that may pull out spokes very soon even
un-anodized while a heavy, thick sectioned rim with anodizing may last a
very long time.
If the question is, "What is better, polishing or anodizing" then the
answer is polishing. If the question is, "What rim will last longer"
then you can only say that you don't know.
Tom Kunich
news:231020010735214983%tmorse...@terrymorse.com...
> John Carrier wrote:
>
> > Despite the conventional wisdom and engineering evidence that would
suggest
> > H/A rims are prone to failure, I've had a pair of the old Mavic Open
4CD's
> > and a pair of Campy Hardox rims that were heroic and their strength
and
> > resistance to abuse ... lasted for many seasons.
>
> How many miles per season?
Although I am big and heavy I got 5,000 miles on a rear Matrix rim AFTER
it had cracked almost totally out of a spoke hole. There was a large
elliptical crack running from between the two spoke holes over to
between the next spoke holes with barely a thread hanging on. The danged
thing stayed straight so I kept using it. Though I did avoid taking that
bike on a ride where there would be fast bumpy downhills.
Now, I do ride lightly -- I am alert and generally avoid potholes, jump
over large cracks and the like -- but it is sometimes amazing what a rim
will do.
Trevor Jeffrey
>Hard anodized rims usually have surface cracks near the spoke holes.
>Eventually these grow and the spokes pull through. It has happened to every
>HA rim that I've owned, except for one that taco'd earlier due to a stupid
>mistake on my part (didn't tighten the QR hard enough on a bike with low
>gearing and a horizontal dropout, and the wheel pulled out, jammed in the
>chainstays, and taco'd).
>
>alex
>
Both failures due to overtensioned spokes, when will you learn?
Bluto
> This is wrong. Anodizing simply grows a layer of aluminum oxide on the
> surface. Hard anodizing (or hardcoating) is just a thicker layer (>.001").
Okay. I just checked in at AACOA's site, which verifies your
assertion. I had seen electron micrographs which showed a
honeycomb-like surface before dyeing, and I had believed that the
voids were established in the base metal.
I wonder why this is fundamentally different than the "anodizing" that
happens to say, a copper plating anode-- in that case, metal ions are
stripped out of the anode and the resulting surface is absolutely
clean and free of oxides.
> I don't have numbers, but intuitively stiffness improvement seems a real
> reach given the relative cross sections of the rim and the anodized layer.
That's a fair assessment, but I have also seen chrome-plated plastic
(motorcycle) parts that suffer noticeable loss of rigidity when the
chrome is peeled away. FWIW. It's plain, though, that a pure AlO2
layer must crackle before taking any significant strain, whatever its
thickness.
Chalo Colina
Jon Isaacs
>(motorcycle) parts that suffer noticeable loss of rigidity when the
>chrome is peeled away. FWIW. It's plain, though, that a pure AlO2
>layer must crackle before taking any significant strain, whatever its
>thickness.
The difference here is the relative stiffnesses and thicknesses.
The chrome plating on plastic is likely thicker but most importantly, the
modulus of most plastics is on the order of 100,000 psi to 500,000 psi which is
about 1/100 th to 1/20th the modulus of aluminum (10,000,000 psi.)
What this means is that the chrome with its Young's modulus of 36,000,000 will
be on the order of 100 times stiffer than the plastic. And since it is bending
we are discussing, the stiffness of the surface layer is very important. The
chrome plating could be responsible for most of the stiffness.
In the case of the bicycle rim, the stiffnesses are much closer, only a factor
of 4 or 5.
jon isaacs
Peter Cole
>
> I wonder why this is fundamentally different than the "anodizing" that
> happens to say, a copper plating anode-- in that case, metal ions are
> stripped out of the anode and the resulting surface is absolutely
> clean and free of oxides.
This is electroplating, a fundamentally different process. Normally,
aluminum will oxidize immediately in air. This process is self-limiting,
since the oxide layer does not permit any oxygen to pass. In anodizing, the
oxidation reaction is "pumped" using acid (usually sulfuric) and an
electrical current, to force the oxide layer to grow further. It still
self-limits at some point, hard anodizing gets the thickest coating by
upping the current and lowering the acid bath temperature.
Electroplating transports metal ions, usually via a solution of metallic
salts. The anode supplies replacement ions as the ions in solution are
deposited from the solution. Anodizing transports oxygen ions, through an
intermediate form (aluminum sulfate, I think, when using sulfuric acid).
> > I don't have numbers, but intuitively stiffness improvement seems a real
> > reach given the relative cross sections of the rim and the anodized
layer.
>
> That's a fair assessment, but I have also seen chrome-plated plastic
> (motorcycle) parts that suffer noticeable loss of rigidity when the
> chrome is peeled away. FWIW. It's plain, though, that a pure AlO2
> layer must crackle before taking any significant strain, whatever its
> thickness.
I think chrome plate is substantially thicker than the max hard anodize
thickness. There is likely also some conductive substrate on the plastic
before chroming.
It seems to be well established in the industry that hard anodizing will
lower the fatigue strength by 50% or so, while improving wear and corrosion
characteristics. This is a poor tradeoff for the application of bicycle
wheel rims.
alex wetmore
<20011025124345...@mb-fr.aol.com>:
Spoke pull through is a sign of a poorly designed rim, not overtensioned
spokes. My other wheels are built with the spokes at maximum tension (wheel
tacos if the tension is higher) and last a lot time.
alex
Tho X. Bui
Peter Cole wrote:
>In anodizing, the
> oxidation reaction is "pumped" using acid (usually sulfuric) and an
> electrical current, to force the oxide layer to grow further. It still
> self-limits at some point, hard anodizing gets the thickest coating by
> upping the current and lowering the acid bath temperature.
I think regular anodizing uses sulfuric acid. To enhance thicker oxide
growth, chromic acid is commonly used for hard anodizing. Same concept
applies per your fine description.
Tho
Bluto
> salts. The anode supplies replacement ions as the ions in solution are
> deposited from the solution. Anodizing transports oxygen ions, through an
> intermediate form (aluminum sulfate, I think, when using sulfuric acid).
When I did my little bit of anodizing and electroplating (in art
school) I remember noting that the H2SO4 solution for aluminum
anodizing was similar to the pickling solution we used to descale
copper and brass after heating. When the pickle became comtaminated
with iron or began to lose its effectiveness after much use, it was
transferred to a barrel where I learned to hook up a power supply and
copperplate things. This was an operation entirely apart from the
proper, cyanide-based plating setup that I used for silver and gold
plating.
Whether because of the electrolyte content or the concentration of
copper sulfate, the old pickle was an excellent plating bath. The
anode would become somewhat porous, but it never formed an oxide.
Aluminum must be entirely different in this respect from copper,
though to be honest I never did try to copper flash aluminum using
that bath. I suppose it wouldn't have worked.
Chalo Colina
Peter Cole
> copper sulfate, the old pickle was an excellent plating bath. The
> anode would become somewhat porous, but it never formed an oxide.
> Aluminum must be entirely different in this respect from copper,
> though to be honest I never did try to copper flash aluminum using
> that bath. I suppose it wouldn't have worked.
Electrochemistry is a huge science, there are many possible processes for
aluminum other than anodizing, there are techniques for plating as well as
"subtractive" processes (like ec machining and polishing). Plating aluminum
is generally a special process, complicated by the fact that the oxide layer
is a good insulator, generally there must be a surface treatment first.
Copper plating is so simple that anyone can do it in a kitchen.