Brake pads eating rims?

Hi all,

Bought a new road bike this year:
Shimano WH-R550 wheelset
Tektro RX40 brakes

Rode maybe 50 miles, and found that my braking power was weak. Also, I
heard what I can only describe as a horrible scraping sound.

So I remove my wheels and inspect my brake pads. What do I find?
Several chunks of bright, shiny metal (I assume from my rims).
My LBS tells me that "Yeah, they're crappy brakes" (actually referring
to the brake pads). He gave me some DA pads for replacement.

I cleaned up the rims, put the new pads on the bike and voila!
Instantly better stopping power......

Rode yesterday morning...everything was okay until a 50mph twisty
descent. Near the bottom I did some *moderate* braking (slightly more
pressure than my typical controlled traffic light stop, just to get me
back down to 35-40 mph). Suddenly, I hear that horrible "eating your
rims" sound.

Since I'm in the middle of a long ride and have no extra pads, I stop
and dig out the shards of metal in my rear brake pads. Then, I proceed
to test 'em out, only to discover that the front brakes have become
relatively weak/noisey. Stop again, and find that the front pads are
wearing in an irregular pattern (more wear on bottom than on top...but
no metal this time). Both sets of pads appear to be properly aligned
with the rim when engaged.

WTF? Does this happen to anyone else? Why are my rims being eaten? I
don't care about replacing worn brake pads once in a while, but
replacing my new rims on my new bicycle......grrrrr.

FWIW, I have heard about using KoolStop Salmons, but my LBS didn't have
any. I'm not convinced that they'd be much better than the DA
pads....to me it seems like a rim problem. Should my LBS deal with
this, or am I stuck with crappy rims?

TIA,
Dave

do you see spots where chunks of metal departed from the rim? a
magnifier?

There is some definite pitting on the rim; not a lot, but enough to
indicate some metal has been stripped. It's difficult to describe the
size of the pits...they are visible on close inspection, but not
terribly apparent otherwise.

Also, running the rim through my fingers (and visually), I can detect
some "banding" of the rim....grooves, if you will. I am a newbie, but
I don't believe that the grooves are outside the realm of normal rim
wear; I haven't done a lot of braking with metal in the pads. Rims
aren't expected to be perfectly smooth and polished like disc rotors,
are they?


wrote:
do you see spots where chunks of metal departed from the rim? a
magnifier?

wrote:

FWIW, I have heard about using KoolStop Salmons, but my LBS didn't have
any. I'm not convinced that they'd be much better than the DA
pads....to me it seems like a rim problem.

No, it's the pads. It's been a mystery for a long time why Shimano can
make some pretty good hardware and yet have such terrible brake pads.

As for Kool Stop salmon pads, they're worth tracking down. Harris
Cyclery has them (http://harriscyclery.net), but it would be better to
talk your LBS into carrying them.

--
Warren Block * Rapid City, South Dakota * USA

wrote:
FWIW, I have heard about using KoolStop Salmons, but my LBS didn't have
any. I'm not convinced that they'd be much better than the DA
pads....to me it seems like a rim problem.

The Koolstop salmons really are that much better.

There's not that much difference between various aluminum alloys to make
a difference when some grit starts chewing up the rims. You could try
going to a ceramic coated (anodized) rim; Jobst says these have problems
cracking, and changing rims and building up a new wheel is a lot more
expensive than installing good brake pads.

Should my LBS deal with
this, or am I stuck with crappy rims?

IMHO, the LBS should deal with the problem by stocking salmon brake
pads, and selling them to you or anybody else that has rims being chewed
up by inferior OEM brakes.

In the mean time, order some Koolstops and either put them on yourself,
or have your LBS install them.

Pat

search bike.tech to
"stop on a quarter" do not include quotes in the search box

the rim metal may have embedded impurities from say fishing sinkers
embbed in budweiser aluminum.

does shimano rubber have fishing sinkers embedded?

shimano pads are not to be thrown away.

i experienced the problem. a squeek means stop and look NOW not next
week. You get enough waste (not wear and tear) after stoping NOW, next
week is much worse.

pulling the metal fro the pad with a pick solved the problem.

as remembered, the rim's brake surface has a smal pocketc followed in
rotation direction by a linear gouge where the metal particle embedded
itself into the rubber. the linear (or circumferential) gouge becomes
more shallow as the metal particle digs and buries itself into the pad
from rim frcition and presssure.

i concluded the particle was road debris?

wrote:

So I remove my wheels and inspect my brake pads. What do I find?
Several chunks of bright, shiny metal (I assume from my rims).

Suddenly, I hear that horrible "eating your
rims" sound.

Since I'm in the middle of a long ride and have no extra pads, I stop
and dig out the shards of metal in my rear brake pads.

WTF? Does this happen to anyone else? Why are my rims being eaten?

Little pieces of road grit get embedded in the pad. This usually happens
when riding on wet roads, the water spray carries the grit to the rim,
where brake action embeds it. After that, the bit of grit just shaves
away at the rim, and the shavings accumulate around it. Hard-compound
brake pads are much more resistant to this phenomenon, they also brake
very well. If you never ride in the wet, use anything, otherwise get
some KoolStop salmons while you still have rims left.

In article . com,
says...

FWIW, I have heard about using KoolStop Salmons, but my LBS didn't have
any. I'm not convinced that they'd be much better than the DA
pads....to me it seems like a rim problem. Should my LBS deal with
this, or am I stuck with crappy rims?

The koolstop salmons are the way to go. Nashbar has these on sale right now in
a Campy style pad. I don't see why the campy pad would not work with your
current set up. Even with shipping two sets of pads would come in under $30.
-------------
Alex

wrote:
Hi all,

Bought a new road bike this year:
Shimano WH-R550 wheelset
Tektro RX40 brakes

Rode maybe 50 miles, and found that my braking power was weak. Also, I
heard what I can only describe as a horrible scraping sound.

So I remove my wheels and inspect my brake pads. What do I find?
Several chunks of bright, shiny metal (I assume from my rims).
My LBS tells me that "Yeah, they're crappy brakes" (actually referring
to the brake pads). He gave me some DA pads for replacement.

I cleaned up the rims, put the new pads on the bike and voila!
Instantly better stopping power......

Rode yesterday morning...everything was okay until a 50mph twisty
descent. Near the bottom I did some *moderate* braking (slightly more
pressure than my typical controlled traffic light stop, just to get me
back down to 35-40 mph). Suddenly, I hear that horrible "eating your
rims" sound.

Since I'm in the middle of a long ride and have no extra pads, I stop
and dig out the shards of metal in my rear brake pads. Then, I proceed
to test 'em out, only to discover that the front brakes have become
relatively weak/noisey. Stop again, and find that the front pads are
wearing in an irregular pattern (more wear on bottom than on top...but
no metal this time). Both sets of pads appear to be properly aligned
with the rim when engaged.

WTF? Does this happen to anyone else? Why are my rims being eaten? I
don't care about replacing worn brake pads once in a while, but
replacing my new rims on my new bicycle......grrrrr.

FWIW, I have heard about using KoolStop Salmons, but my LBS didn't have
any. I'm not convinced that they'd be much better than the DA
pads....to me it seems like a rim problem. Should my LBS deal with
this, or am I stuck with crappy rims?

TIA,
Dave

When you replace your pads, also carefully sand the rims down with very
gritty sandpaper in the direction of rotation. The objective is to
smooth out those pits. I found that the pits have burrs on them which
embed in the new pads, which in turn exacerbate the problem. So, if
your rims are sanded down and cleaned to remove all those microscopic
pieces of aluminum (incidentally aluminum oxide has a hardness index
close to quartz) and you put clean pads on, that should do the trick.

Neil Collin writes:

When you replace your pads, also carefully sand the rims down with
very gritty sandpaper in the direction of rotation. The objective
is to smooth out those pits. I found that the pits have burrs on
them which embed in the new pads, which in turn exacerbate the
problem. So, if your rims are sanded down and cleaned to remove all
those microscopic pieces of aluminum (incidentally aluminum oxide
has a hardness index close to quartz) and you put clean pads on,
that should do the trick.

Don't do that. There is no need to remove any more material from the
rim, it is already damaged enough. If you use Kool-Stop salmon
colored pads, there is no need for any of that. In fact the rougher
the rim (longitudinal grooved) the easier it will be to brake hard
right away with new pads an the smaller the tendency to squeal.
That's why rims are machined these days, because it suppresses squeal
for new bicycle demo's.

I don't know what benefit you imagine by sanding the rim. There are
no "pits" in the rim. There are only grooves from aluminum oxide
cutting tools embedded in poor brake pads.