Cracks on rim

In article said:

Quoted message said:

Rims shouldn't break unless exposed to huge forces- like getting run over by a truck.

Or sustained braking when riding in dirt.

That should not crack a rim.

Quoted message said:

Quoted message said:

It is not bad luck.

Getting a branch into a wheel is rarely done on purpose.

Which should not crack a rim.

I don't know what you think is causing your rim to fail, but it's not sticks getting caught in the
spokes and it's not sustained braking.

Well, I should clarify the latter point- you *can* wear down the brake track to the point that the
sidewall cracks from the force of the tire bead pulling on it, splintering off 2-3 mm of the outer
edge of the sidewall. This happens on road wheels just as readily, especially wheels ridden down
mountians in the rain where grit gets on the rim. Sustained braking will not cause cracking around
the spoke holes, which is my recollection of what you're posting about.

Again, you can find out as much information as you want- and more- in a few seconds with a Google
search on this newsgroup (just go to Google and click on the "Groups" link, from there you can
easily select the newsgroup and do a simple search for "rim cracks" or some such- you'll get
thousands of hits. I believe this is also discussed in the r.b.t FAQ. It's probably discussed on
Sheldon "Encyclopedia" Brown's Web site, too.

In article <[email hidden]>,

Chris B. said:

Mavic - the 'Bose' of bicycle rims.

Not quite. Bose actually makes good products.

"Tim McNamara" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

In article <[email hidden]>, Again, you can find out as much information as
you want- and more- in a few seconds with a Google search on this newsgroup (just go to Google and
click on the "Groups" link, from there you can easily select the newsgroup and do a simple search
for "rim cracks" or some such- you'll get thousands of hits. I believe this is also discussed in
the r.b.t FAQ. It's probably discussed on Sheldon "Encyclopedia" Brown's Web site, too.

I don't think ceramic sidewall coatings have any effect on eyelet cracking. Are you sure you're not
confusing anodizing and its brittle surface layer susceptibility to fatique crack propagation with
ceramic sidewalls problems?

Scott..

Quoted message said:

Sustained braking will not cause cracking around the spoke holes, which is my recollection of what
you're posting about.

thought the thread had changed to the pro and cons of ceramic rims. i think they are more durable.
you don´t. did you do some research on it, or support your view on some reseach?

Per

Per Löwdin said:

Without being a wheel engineer I think it is safe to assume that there is a trade-off between
durability and weight.

Surely, among other things. A Mavic 517 rim is a high end lightweight rim, designed for XC racing,
395 g catalog weight. That is pretty damn light. Especially for loaded offroad touring. Match the
tool to the use: a Mavic 618 weighs 460 g. A pair of these weighs 130 g more, about two clif bars.

In article <[email hidden]>,

S. Anderson said:

"Tim McNamara" <[email hidden]> wrote in message
"]news:[email hidden]...

<snip>

Quoted message said:

I don't think ceramic sidewall coatings have any effect on eyelet cracking. Are you sure you're
not confusing anodizing and its brittle surface layer susceptibility to fatique crack propagation
with ceramic sidewalls problems?

I'm not having any trouble with any such confusion.

In article said:

Quoted message said:

Sustained braking will not cause cracking around the spoke holes, which is my recollection of
what you're posting about.

thought the thread had changed to the pro and cons of ceramic rims. i think they are more durable.
you don´t. did you do some research on it, or support your view on some reseach?

Again, why rehash what's already been discussed lierally hundreds of times in this newsgroup? You've
been around here long enough to have seen many of those previous discussions too. If you can't
remember them, use Google to refresh your memory.

Quoted message said:

Surely, among other things. A Mavic 517 rim is a high end lightweight rim, designed for XC racing,
395 g catalog weight. That is pretty damn light.

Quoted message said:

Especially for loaded offroad touring.

We are not going offroad with luggage. Don´t care much for fire roads or 4WD roads, though we might
do a few backroads in Colorado just for the views and the feeling and to get away from traffic, but
mostly we will ride good roads when we go from place to place and then go off road without luggage.

Quoted message said:

Match the tool to the use: a Mavic 618 weighs 460 g. A pair of these weighs 130 g more, about two
clif bars.

I just found a 618 in Stockholm, at a reliable shop (used to building wheels, not all can do it
right) and they build it in one day. The weight difference is completely neglectable.

Thanks everyone for your comments.

Per user.tninet.seMTB.htmlOpen ↗

Quoted message said:

That makes good marketing sense. Anyone who buys into the "benefits" of ceramic braking surface
may also be swayed by the "appeal" of hard anodizing.

Not necessarily, we got into ceramic rims after a wheel got ruined in Ladakh, India. Did some really
high passes, lost altitude from Khardong La 5602 m to Nubra just under 3000. After a number of high
passes my rear rim was burned up, coming apart. Since then we have used ceramic rims and they
withstand the friction better. The wheel that had cracks around the eyelets now was hardly worn on
the braking surfaces.

Quoted message said:

Add to that the "advantage" of low spoke count, and you have a real winner.

Yes, you are right, I learned the hard way, got a Fisher some years ago with Bontrager Racelite
wheels, with 24h and 28h, and CK hubs, thought it was

new rim from the US to have it rebuilt. Cost a lot! Since then we build with
32h.

Per user.tninet.seMTB.htmlOpen ↗

Terry Morse said:

Peter Chisolm said:

hard anodizing with eyelets are not a good idea. non anodized, ceramic rims in 28h may be a
tough one to find.

That makes good marketing sense. Anyone who buys into the "benefits" of ceramic braking surface
may also be swayed by the "appeal" of hard anodizing. Add to that the "advantage" of low spoke
count, and you have a real winner.

For people living in dry climates like California, ceramic rims may not seem like a good idea. In
rainy places with actual winters, like Scandinavia, they are. An ordinary rear rim lasts about 4000
km here while a ceramic rim lasts about 12 000 km, in my experience. The issue is sidewall wear from
rim brakes.

Bård Brørs

Quoted message said:

An ordinary rear rim lasts about 4000 km here while a ceramic rim lasts about 12 000 km, in my
experience. The issue is sidewall wear from rim brakes.

Precisely, could not agree more, last five years I have used ceramic coated rims.

Per user.tninet.seFirst.htmlOpen ↗

Tim McNamara said:

In article <[email hidden]>,

Chris B. said:

Mavic - the 'Bose' of bicycle rims.

Not quite. Bose actually makes good products.

They also make really crappy products, depending on price ranges (so far, so Shimano), but most
importantly, they ridiculously overprice everything. Don't think that's really Mavic's style, but
some might disagree.

Jasper

In article said:

Quoted message said:

hard anodizing with eyelets are not a good idea. non anodized, ceramic rims in 28h may be a
tough one to find.

Had no idea anodizing made aluminium brittle. As far as I am concerned the rims may be furry, or
whatever, as long as the side wall surfaces are ceramic coated.

This has been discussed hundreds of times in this newsgroup, with long-running and mostly boring
threads. A Google search of r.b.t. will turn up much information (and misinformation).

Anodizing is the creation of a (relatively) thick aluminum oxide coating over an aluminum substrate.
Aluminum oxide is brittle and cracks easily; the resulting fractures spread through the aluminum
underneath and the rim breaks, typically around the spoke holes. Aluminum oxide can have dyes added
to provide a variety of colors. It is much harder than aluminum, and is a poor conductor of heat and
a nonconductor of electricity.

Aluminum oxide is a ceramic, BTW. It provides a poor braking surface that is slippery when wet,
which is part of why the sidewalls of rims now tend to be machined. Anodized rims and ceramic coated
rims are poor conductors of heat, which is why they chew up brake pads so badly.

Quoted message said:

Anodizing is the creation of a (relatively) thick aluminum oxide coating over an aluminum
substrate. Aluminum oxide is brittle and cracks easily; the resulting fractures spread through the
aluminum underneath and the rim breaks, typically around the spoke holes. Aluminum oxide can have
dyes added to provide a variety of colors. It is much harder than aluminum, and is a poor
conductor of heat and a nonconductor of electricity.

Ok, what is the implication for anodized frames? Are they more or less durable than those that are
not anodized?

Per user.tninet.seMTB.htmlOpen ↗

In article said:

Quoted message said:

Anodizing is the creation of a (relatively) thick aluminum oxide coating over an aluminum
substrate. Aluminum oxide is brittle and cracks easily; the resulting fractures spread through
the aluminum underneath and the rim breaks, typically around the spoke holes. Aluminum oxide can
have dyes added to provide a variety of colors. It is much harder than aluminum, and is a poor
conductor of heat and a nonconductor of electricity.

Ok, what is the implication for anodized frames? Are they more or less durable than those that are
not anodized?

Excellent question that I don't know the answer to. I wonder if it makes a significant difference in
frames, guessing that the walls of the frame tubes are thicker than rims.

Mr. Willet is much more charitable towards anodizing than I am, and perhaps has already considered
this question.

Per Löwdin' may have said:

Quoted message said:

Anodizing is the creation of a (relatively) thick aluminum oxide coating over an aluminum
substrate. Aluminum oxide is brittle and cracks easily; the resulting fractures spread through
the aluminum underneath and the rim breaks, typically around the spoke holes. Aluminum oxide can
have dyes added to provide a variety of colors. It is much harder than aluminum, and is a poor
conductor of heat and a nonconductor of electricity.

Ok, what is the implication for anodized frames? Are they more or less durable than those that are
not anodized?

Per user.tninet.seMTB.htmlOpen ↗

A submicroscopic film of aluminum oxide will form spontaneously on bare aluminunm within seconds
after exposure to air; anodizing merely increases the thickness of it and regularizes it. Yes,
aluminum oxide is brittle, and anodizing an aluminum part that will be subject to flexing will
produce a crazing of the coating when the part deforms sufficiently under load, but my experience
with anodized aircraft parts and automotive racing components suggests that the amount of flexing to
which a bike frame is subjected should be unlikely to have this result. The tendency to craze is
additionally impacted by the thickness of the coating, which can be very thin indeed; the thinner
the anodization, the less that you'll be likely to notice crazing. Others with more direct
experience with anodized bike frames may be able to shed more light on the relevance of that
specific issue. In my opinion, though, rims and front forks would be more likely to craze, and
perhaps MTB handlebars and the lighter-duty stems. Anodizing's main positive feature would be in the
resistance of the surface to *minor* abrasion and improved resistance to corrosion, but the drawback
is that an anodized aluminum surface is a royal [censored] to paint. (That's one of the big reasons for
inclusion of dye in the anodizing.)

It is important to remember that flexing of an aluminum part that is sufficient to craze the
anodizing might also be sufficint to stress the aluminum to the point where microfractures could
form. In that case, the crazing may be a warning that greater problems might be present below it.
Parts as robust as a crank arm probably are not worth worrying about in this regard; something as
thin as a rim or front fork tube might be a different matter. Testing for cracks in aluminum will
only find problems that reach to the surface, and crazing of the anodization may give a false
indication with dye-check methods.

---
My email address is antispammed; pull WEEDS if replying via e-mail.

Yes, I have a killfile. If I don't respond to something, it's also possible that I'm busy.

"Bård Brørs" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

For people living in dry climates like California, ceramic rims may not seem like a good idea. In
rainy places with actual winters, like Scandinavia, they are. An ordinary rear rim lasts about
4000 km here while a ceramic rim lasts about 12 000 km, in my experience. The issue is sidewall
wear from rim brakes.

And, what's more, the fact that sand is scattered on the roads and pedestrian areas to improve grip.
This wears ordinary brake blocks and sidewalls down very fast!

SteveC (Norway)