whining about my disc brakes

Last night, I left work early with the plan of doing three loops of
Betasso. Stress from work had me jonesing for some movement; I needed
to wash that work right out of my hair!

Got there, noticed my front wheel was squealing -- I'd spin it and it
would only make it a couple of turns before the friction stopped it.
Played with the brake calipers, couldn't seem to make it much better, so
I rode up the first climb. The squeal was driving me nuts, so I stopped
again and fiddled. No real luck. Started again, started going
downhill, then stopped. The front brake required way too much pull to
engage. So, the first maintenance I've done by myself -- I whipped out
the Alien and pulled some of the brake wire through the screw to tighten
up the line. That worked as far as it went, but the brakes still felt
mushy, despite the fact that they were still squealing. I guess the
imbalance was messing up my braking technique, too, because I was
fishtailing all over the place. Bleh. Survived the first descent and
the next mini-climb, then fiddle again. By this time I'm just
frustrated, scared, and probably not using a very scientific method to
fix 'em, so predictably, they don't shape up.

End result: only one lap, pretty miserable. Drive home in a ****-poor
mood.

I get home and Eric had the calipers adjusted to get rid of the constant
squeal within about 5 minutes *sigh*. But now there's another squeal --
more intermittent, and quieter, so I suppose it might not even be the
brakes. I can't even swear it's in the front. Seems to be more
pronounced when I lean right. But at least the wheel spins freely, so I
guess I'll just ignore it.

This isn't the first time I've had to mess with the brakes.

So, my questions to disc brake users: Are your brakes typically silent
when not braking, or do you get some noise? Do you have to adjust them
frequently, or do they behave themselves once you have them set up? Is
there a break-in procedure I should have followed? Can rotors be warped
in such a way that you can't see the warping?

These are Avid mechs, fwiw.

--
monique

"Get a bicycle. You will not regret it, if you live."
-- Mark Twain

On 2004-08-04, Doug Taylor penned:
"Monique Y. Mudama" wrote:

These are Avid mechs, fwiw.

You are not alone. It takes some tweaking to get the calipers aligned
and the pads adjusted just so. Until you do, you'll get some
rubbing, squealing and squeaking.

Also, you don't adjust the pads by tightening or loosening the cable.
The mech discs are a different animal than your rim brakes.

Er, did I say that?

I described two different problems. I adjusted the calipers by turning
the big red knobs to either side of the rotor. I adjusted the *cable
tension* by tightening the cable, so that I wouldn't have to pull the
brake all the way to the handlebar to get it to work. I suppose that
all the recent riding had stretched the cable; the front brake was able
to pull inward much farther than the rear was.

Here is the cite to the Avid tech manuals that give step by step
instructions:

http://www.avidbike.com/7_techinfo/tech7_2_manual.html

There are separate manuals for 160 mm, 165mm and 185/203 mm rotor
brakes.

Thanks for the link. I'd have to look up my rotor size.

--
monique

"Get a bicycle. You will not regret it, if you live."
-- Mark Twain

"Monique Y. Mudama" wrote:

These are Avid mechs, fwiw.

You are not alone. It takes some tweaking to get the calipers aligned
and the pads adjusted just so. Until you do, you'll get some
rubbing, squealing and squeaking.

Also, you don't adjust the pads by tightening or loosening the cable.
The mech discs are a different animal than your rim brakes.

Here is the cite to the Avid tech manuals that give step by step
instructions:

http://www.avidbike.com/7_techinfo/tech7_2_manual.html

There are separate manuals for 160 mm, 165mm and 185/203 mm rotor
brakes.

--dt

to pull the brake all the way to the handlebar to get it to work. I
suppose that all the recent riding had stretched the cable

That's not likely. The Avid CPS adjusters are there specifically so that
you don't have to adjust the cable pull.

You have to watch the pad clearance to the disc. Get a white background
(linoleum works), and watch the caliper from the top. IF you can see any
more than half a millimeter of daylight through the caliper on either side
of the disc rotor, then you have too much play in it, but you should at
least see daylight on both sides of the rotor. Screwing in (clockwise) the
red adjuster knobs will bring the pads closer to the rotor, making your
braking travel feel "tighter." Your rotor should also deflect minimally
once the outside pad hits the disc.

If Eric adjusted the pads properly, your rotor is likely out of true. Check
to see if it isn't warped... long downhills can release residual stresses
formed when the rotor was cast. It doesn't have to be totally perfect - all
rotors I've seen have a tiny wobble to them, new and old.

The squealing shouldn't occur if you're riding straight. An intermittent
squeal can mean an out-of-true rotor, the magnitude of which should be
determined by a bike-savvy person.

What am I'm saying? This bike is new. Take it to the LBS if your problems
continue... they should offer a free tune-up on new bikes for at least a
year. Good luck!

--
Phil, Squid-in-Training

Monique Y. Mudama wrote:
Last night, I left work early with the plan of doing three loops of
Betasso. Stress from work had me jonesing for some movement; I needed
to wash that work right out of my hair!
SNIP
So, my questions to disc brake users: Are your brakes typically silent
when not braking, or do you get some noise? Do you have to adjust them
frequently, or do they behave themselves once you have them set up? Is
there a break-in procedure I should have followed? Can rotors be warped
in such a way that you can't see the warping?

These are Avid mechs, fwiw.


My discs squeel all of the time no matter how much adjusting I do. Dust
doesn't help, either. I've just learned to ignore it.

--
o-o-o-o Ride-A-Lot o-o-o-o
www.schnauzers.ws

Ride-A-Lot wrote:


My discs squeel all of the time no matter how much adjusting I do. Dust
doesn't help, either. I've just learned to ignore it.


Well, yeah, kinda.

Not too long ago Dan swapped out my V-Brake on the front for an Avid
disk brake. It does tend to make a lot of noise. Squeaks and squeals
and groans that can't be adjusted out. At least not by yours truly.


It's also got much finer modulation than my old v-brake. I found out
about this not too long ago, during a sudden downpour. I was coming
down a short slope and started to slide out on the mud. Grabbed the
brakes and found myself wondering why the ground was coming up so fast.

I don't mind the brake noise. What annoys the crap out of me is the
intermittent squeaky pivot.

Kathleen

Monique Y. Mudama wrote:
(snip)

These are Avid mechs, fwiw.

--
monique

"Get a bicycle. You will not regret it, if you live."
-- Mark Twain

My Avid mechs are quiet. Put some mud all over the discs
ride the bike and start applying the brakes to "prime" the pads.
You may need to realign the brakes themselves too.

--
- Zilla
Cary, NC
(Remove XSPAM)

Kathleen wrote:
Ride-A-Lot wrote:


My discs squeel all of the time no matter how much adjusting I do.
Dust doesn't help, either. I've just learned to ignore it.


Well, yeah, kinda.

Not too long ago Dan swapped out my V-Brake on the front for an Avid
disk brake. It does tend to make a lot of noise. Squeaks and squeals
and groans that can't be adjusted out. At least not by yours truly.


It's also got much finer modulation than my old v-brake. I found out
about this not too long ago, during a sudden downpour. I was coming
down a short slope and started to slide out on the mud. Grabbed the
brakes and found myself wondering why the ground was coming up so fast.

I don't mind the brake noise. What annoys the crap out of me is the
intermittent squeaky pivot.

Kathleen


I run Hydrolics on all my bikes , so adjusting is even more difficult
than on the mechs. I've shimmed and bled till I can't shim and bleed no
more, and still it squeaks. Seems to be more prominent when I'm going
uphill.

--
o-o-o-o Ride-A-Lot o-o-o-o
www.schnauzers.ws

On 2004-08-04, ZeeExSixAre penned:
to pull the brake all the way to the handlebar to get it to work. I
suppose that all the recent riding had stretched the cable

That's not likely. The Avid CPS adjusters are there specifically so
that you don't have to adjust the cable pull.

I'm confused. You say the CPS, but are you referring to the part where
it says, "IMPORTANT: Only use the barrel adjuster at the brake lever to
adjust for cable slack. For lever throw, use the outboard adjustment
knob"?

I guess I have trouble buying this. I don't see how a teensy adjustment
like that is going to shorten the distance I have to pull the brake by
an inch or so (not exactly sure of distance).

I do have to ask: what happens if you adjust the cable length for lever
throw? Other than going to hell for not following the instructions, I
mean?

You have to watch the pad clearance to the disc. Get a white
background (linoleum works), and watch the caliper from the top. IF
you can see any more than half a millimeter of daylight through the
caliper on either side of the disc rotor, then you have too much play
in it, but you should at least see daylight on both sides of the
rotor. Screwing in (clockwise) the red adjuster knobs will bring the
pads closer to the rotor, making your braking travel feel "tighter."
Your rotor should also deflect minimally once the outside pad hits the
disc.

Half a millimeter, huh? I don't know that my eyes are that good! There
is daylight shining through on both sides, but they're certainly not set
at their loosest. Whenever I fiddle with them, I try pushing the bike
forward as hard as I can while holding onto the brake lever. If the
wheel spins at all, I figure it's too loose. Is there a better way to
test this, other than finding out on the mountain slope that you have
insufficient braking power?

If Eric adjusted the pads properly, your rotor is likely out of true.
Check to see if it isn't warped... long downhills can release residual
stresses formed when the rotor was cast. It doesn't have to be
totally perfect - all rotors I've seen have a tiny wobble to them, new
and old.

In spinning it, I can't identify any obvious warpage. Spinning the
wheel with the bike's front in the air doesn't cause squeaking and
doesn't demonstrate contact, either.

The squealing shouldn't occur if you're riding straight. An
intermittent squeal can mean an out-of-true rotor, the magnitude of
which should be determined by a bike-savvy person.

What am I'm saying? This bike is new. Take it to the LBS if your
problems continue... they should offer a free tune-up on new bikes
for at least a year. Good luck!

That's not their official policy (I think it's one free tune-up), but
whenever I've gone to them they've been very helpful. That being said,
I get the feeling this is the sort of thing I should know how to deal
with on my own.

And *that* being said, is it a good idea to keep a spare rotor or two on
hand in case one does warp? How frequently do they tend to warp? I
guess I'm not clear one whether you need an exact model of rotor for a
specific system, or if you get some leeway there.

Thanks for the guidance! I really do want to figure this stuff out. I
feel like I'd better know how to fix my brakes before something goes
seriously wrong far into a trail.

--
monique

"Get a bicycle. You will not regret it, if you live."
-- Mark Twain

"Monique Y. Mudama" wrote in message
...

snip!

So, my questions to disc brake users: Are your brakes typically silent
when not braking, or do you get some noise? Do you have to adjust them
frequently, or do they behave themselves once you have them set up? Is
there a break-in procedure I should have followed? Can rotors be warped
in such a way that you can't see the warping?

These are Avid mechs, fwiw.

--
monique



Just let it go! You're gonna drive yourself nuts if you constantly focus on
all the "squeaks and squeals"....