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*Edit Me* - New FAQ addition on brake squeal.



 
 
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  #1  
Old July 22nd 03, 09:20 PM
ant
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Posts: n/a
Default *Edit Me* - New FAQ addition on brake squeal.

Howdy. i posted a couple days ago asking for tips and thoguhts on
brake squeal. i was not, as i had naievely hoped, immediately
inundated with secretive tricks and age-old wisdom, so i did the best
i could with my own knowledge and the archives, and present the
following for you to pick apart. post if there are any glaring
mistakes, additions, etc. when i quoted sections from posts, i
attributed with a name and email address. if it shoudl be just a name,
or just an email, or neither, let me know.

best

anthony

---

Practical Steps towards quieting squealing brakes.

Toeing in brakes is the most basic and widely known advice. A few
specifics regarding various types of brakes:

V-brakes. Start with no pad toe-in. If they squeal, try toeing them in
a little. Aim for no more than 1/32". A lot of toe in is unacceptable
as there is not much cable travel to spare and you get mooshy action.

Cantis. Start with them slightly toed in. Possible starting point
might be width of a dime at first contact of front of pad. Popular
wisdom seems to be quite supportive of toe angle experimentation with
cantis. If they squeal, try a steeper angle. 1-3mm is a good realm to
stay in.

Road brakes. Start with no toe in. Many calipers do not have hardware
(spherical washers) to toe in pads. There are many aftermarket brake
pads that toe in easily, so that is one good option if they squeal.
Unlike beefy brakes like cantis and v's, you can generally bend a road
caliper to toe the pad in. This is, of course, a cinch with flimsy
department store calipers. It was common practise with older road
calipers like centerpulls, and there is even a park tool made
specifically to do this. Modern road calipers, dual pivots especially,
are pretty beefy and don't take as kindly to 'metalworking'. Some new
calipers come noticeably off kilter, either toed in the wrong way, or
otherwise misaligned. It is said that cold setting these new calipers
is a bad thing, as anytime you bend aluminum there is some risk of
damage- present or future. However, I see mechanics in shops bend
(very small bends, mind you) modern road calipers with regularity. No
problems- Yet. YMMV. An alternative to bending calipers to achieve
road caliper toe in is to take the pads off the calipers and sand them
on a belt sander, or with a block of wood and sandpaper, such that
they are toed in.

Disc brakes. see bottom of article.

If appropriate toe-in doesn't work, things to try, in rough priority:

-clean rim. you might even do this before toeing in. soap and water
generally work. or, you can try an appropriate solvent. Alcohol, and
acetone seem to work. Automotive brake cleaner has also been
suggested. Alcohol is much better for you than acetone, acetone is a
stronger solvent. Brake cleaner doesn't sound like something you'd
want to drink either, but sometimes you have to make sacrifises.
-Make sure pads are correctly oriented. Pads where orientation matters
generally have an arrow that indicates rim revolution direction. Art
Harris writes: "If you have any of the "asymetrical" pads, make sure
the longer end is towards the rear." If there is no indication of
correct orientation, you could try turning them around, or switching
them left for right to see if that changes anything.
-sand rim. or scotchbrite. machined rims have a roughness to them
already, but sanding can sometimes help with these anyway. with some
rims, steel wool, or a 400 grit swipe is all it takes. 125 grit is
the last resort, and your rims better be pre-machined or the fine
scratches will look pretty ugly and nobody will talk to you on the
club ride.
-take brake system apart and rebuild clean, lubed, and tight.
neglected points would be a little grease between pad washers which
can make a difference.
-clean pads. also make sure there is no foreign matter embedded in the
pads.
-sand pads. or scotchbrite. if that doesnt work, file pads. You can
also try sanding areas of the pad away. Sanding a bevel into 1/4 of
the leading edge of the pad has been suggested a few times.
-uneven toe in. toe in one pad only, or one pad more than the other.
-Toe-OUT. yes. toe the pads the wrong way. As little as 1/64" all the
way up to 'generous' toe-out. this decreases braking power, but if you
keep it conservative it should not be a problem with modern brake
systems.
-change pad, either material or construction. a cartridge pad is
stiffer than a disposable brake pad. in addition, some cheaper pads
may have inferior tolerances and not seat as firmly onto the caliper.
changing material can make a big difference.
-for bossed calipers (cantis/v's) a brake booster stiffens the system.
-aftermarket adjustments to brake calipers. Shimano, for example,
sells shims that adjust the play in some of their bossed brakes. This
was specifically to address squealing problems in parallel-push
calipers, IIRC.
-change brake calipers. stiffer might help. or just changing something
can do the trick. higher quality does not necessarily mean less
squealing, but it generally is a step in the right direction.
-you do have aluminum rims, don't you?

Misc. Tips and Tricks.

Popular wisdom on R.B.T

To sand your rims, and clean any contaminants off at the same time,
you can do it while riding. From a variety of posts, your options
include riding in the rain, or through puddles, or mud, while braking
a lot. Putting an abrasive on the rims while riding such as bathtub
cleaner, etc, laying on the brakes, and rinsing it off afterwards with
a waterbottle can work too.

Mellerio:

I have tried everything under the sun to quiet XTR v-brake squeal on
my Cannondale Headshok Fatty SL. A Shimano Carbon Brake Booster works
because it dampens the vibration. This led me to find other solutions
to dampen vibration. I tried rubber bands around the pivot arms, etc.
and nothing
worked.

Today I tried placing a 1/8" O-Ring between the v-brake and the brake
boss mount. I tightened down the v-brake, compressing the O-Ring and
took the bike for a spin (without the carbon booster). No squeal!!!
[Although in the rain they still squealed]

From Mike Jacoubowsky:


First, just for kicks. try reversing the front wheel.

From Gmaker:


-Observe the wheel from above in very good light.
-Very slowly apply brakes.
-Carefully check if the wheel deflects slightly in one direction as a
result of one pad applying more force than the other *just when they
hit*.

This can happen even though the pad standoff appears equal and the
pads seem to move evenly. Adjust pads to stop this.

Counter-intuitive, and unproven, From K. Becker:


Here's an unconventional cure for brake squeal: Put a little wax on
the rims or the pads, rubbing them lightly with a crayon or a candle
works well. I've used this method on several of my neighbor's bikes,
since
the metal used for brakes on cheap bikes is often too brittle to
toe-in. The wax actually seems to improve the performance, although if
you used too much it might decrease it, so apply sparingly.

From Neil, at the shop I work at

If all else fails, or you are in a hurry, brushing a little talcum
power on the brake pad seems to take squeal away. Unsure about how
long it lasts.

The Kool Stop Salmon Legend: A Red Herring?

Koolstop salmon pads are highly recommended on r.b.t for their power
and quality. On my own bike, I can feel a marked difference in power
when running the KS salmons. However, all is not golden. Some or all
of these salmon pads seem to be particularly resistant to de-squealing
with some setups. Many posts volunteer alterations you can make that
may or may not cut down on squeal, including sanding off the plow tip,
sanding a bevel into the pads, sanding in a 'toe-in', etc. Many
suggest koolstop dual compound pads for bikes in need of quality pads
but with serious squealing issues with the full-salmons. Another
possibility to reap the benefits of grippy salmon is to use the KS
salmon cartridges with a stiff metal cartridge holder.


Things that can cause a brake that wasn't squealing before to start
squealing;

-coating the rim with a substance that exaggerates the stick-slip
behavior of pad on rim. examples include getting oil or grease on the
rim surface, or biking through wet grasses as mentioned in the FAQ.
Fix: clean the rim.
-Too clean. This is one that has happened to me. It seems that some
amount of dirt or abrasive on the rim can keeps things quiet for
squeal-prone brake systems. I once cleaned the rims on one of my
squeal-prone rides with alcohol, and suddenly my brakes were squealing
after months of silence. I cleaned again. More squeal. I figured it
was impure solvent, so i upgraded to acetone, and cleaned them with
that. still squealing like a pig. I had to lightly sand the rims and
toe them in more to shut them up.
-pads wearing down and developing new resonant properties. re-toe in,
sand, or whatever it takes.
-bad karma. call your mother, clean your bike, feed your dog, and hope
for the best.

Disc brake squeal:

Y'know how all the manufacturers say not to get oil on your
rotors/pads while setting up/bleeding your brakes? Well. Now you know.
Clean them. Clean the pads. Clean everything. Some companies say that
cleaning pads of oil is useless and hint that they might need
replacement. YMMV. Below find some tips. In addition to these, check
that everything is clean, lubed, and tight. As a last resort, you
could try sanding the rotor itself.

From Tony Raven:

1. Clean the disc with [solvents such as] methylated spirits and make
sure it does not get oil or wax on
it - washing the bike with wax containing car shampoo can cause the
problem as can clumsy spray lubrication.

2. After cleaning the disc, take the pads out, place fine emery on a
flat (glass?) surface and rub the pad surface on the emery in a figure
of eight motion to remove any glazing that may have formed.

3. Put the pads back (in the same place as they came from, don't mix
them up) with a smear of copper grease between the pad and the piston.

4. Chamfer the leading edge of the pads

5. Ride in wet abrasive mud


From Rich Wood:


lightly coat the back of the pads with copper grease. You might need
to put a strip of aluminium
tape on there first to stop the grease contaminating the pads.

Thank you to:

Everyone. I couldn't possibly cite everyone who's posts contributed to
this accumulated knowledge, so a big thank you and an electronic hug
will have to do.
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  #2  
Old July 23rd 03, 06:52 AM
Konstantin Shemyak
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Posts: n/a
Default *Edit Me* - New FAQ addition on brake squeal.

A couple of really cosmetic findings:

Cantis. Start with them slightly toed in. Possible starting point
might be width of a dime at first contact of front of pad.


"Width of a dime" is not very widely known length unit, in particular
outside of the US. Is it about 1mm?

-clean pads. also make sure there is no foreign matter embedded in the
pads.


If there is, how to get rid of it? Or is replacing the pads the only cure?

Thanks for the newborn FAQ!

Konstantin Shemyak.

 




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