Disk Brakes: Centering Calipers w/o using pads?

This last set of pads I've put in are giving me fits.
Previous two sets haven't been bad at all.

Can't seem to get this pair centered right.

Now, after a few hundred miles of fooling around, it's to the point when I mic
them, each pad has a different thickness on different edges.

I'm assuming that even new pads aren't perfectly true - so it seems like the
Good-Right-And-Holy path would be some method of getting the calipers centered
and parallel without using pads at all - then put the pads in and let any
unevennesses work themselves out with normal wear.

Am I on the right track?
--
PeteCresswell

"(Pete Cresswell)" wrote in message
...
This last set of pads I've put in are giving me fits.
Previous two sets haven't been bad at all.

Can't seem to get this pair centered right.

Now, after a few hundred miles of fooling around, it's to the point when I
mic
them, each pad has a different thickness on different edges.

I'm assuming that even new pads aren't perfectly true - so it seems like
the
Good-Right-And-Holy path would be some method of getting the calipers
centered
and parallel without using pads at all - then put the pads in and let any
unevennesses work themselves out with normal wear.

Am I on the right track?

I would think you'd need some kind of 'blank' to put in their place that is
the same size/shape and thickness. If you try to squeeze the pistons to the
rotor they may become unseated and leak. It may just be dirt built up
inside the caliper not allowing the pads to travel evenly to the rotor.
Give it a good cleaning inside with alcohol and try new pads. What brand
brakes are they?

Mike

RE/
What brand
brakes are they?

Hope C2's.

Haven't had any probs with (EBS?) "Green"s - and I've been through a few sets,
but both pair of Hope pads I've used have given me fits noise-wise. I think
it's something about the higher metal content being less tolerant of
misalignment.
--
PeteCresswell

"(Pete Cresswell)" wrote in message
...
RE/
What brand
brakes are they?

Hope C2's.

Haven't had any probs with (EBS?) "Green"s - and I've been through a few
sets,
but both pair of Hope pads I've used have given me fits noise-wise. I
think
it's something about the higher metal content being less tolerant of
misalignment.
--
PeteCresswell

My Mini's were the same before I started with the EBC Greens. I used to say
"I 'Hope' they stop squealing!" Do your calipers mount the same as Mini's?
Meaning, do you use shims to center the caliper to the disc rotor? If so
it's possible it's the dirt/binding thing I mentioned that is causing your
uneven wear problem. The other thing Hope Tech told me is to have the
caliper mounts on the frame faced to ensure they are perpendicular to the
wheel axle. Magura makes a tool for that and I believe Hope does now as
well. Check with LBS's in your area for this service.

Mike

RE/
Meaning, do you use shims to center the caliper to the disc rotor? If so
it's possible it's the dirt/binding thing I mentioned that is causing your
uneven wear problem.

Yes, they need shims. Searched far and wide for the precision washers, wound up
with a little bag of open-ended thingies. Less time-consuming to add/remove
while searching for the magic spot, but I'd still like to get some real washers
for permanent use. The open-ended things seem like they'd fall out easily and
they aren't carrying the load evenly.

The other thing Hope Tech told me is to have the
caliper mounts on the frame faced to ensure they are perpendicu

I don't think I want to go there because it already takes a half-dozen shims to
get the pads near center. Worst case, I think I'll just go back to greens and
stick with them. Dunno what got in to me ordering a second set of Hope
pads...pure masoschism, I guess.

Has anybody tried "yellow"...the sound like a step down from "green" in
durability...but I'm guessing each step down in durability carries some upside
in some other characteristic.

--
PeteCresswell

RE/
o have the
caliper mounts on the frame faced to ensure they are perpendicular

I think you've put me on to something with that. I looked more closely at the
insides of the mounts. Ellsworth has coated that area with some very heavy
plastic-like coating - much thicker than any paint I've ever seen.

Turns out the stuff is starting to peel off there - causing an irregular surface
where the calipers and shims bear.

I trimmed it with a razor blade and then took a leaf out of the Avid book: I
slackened the mounting screws a lot, then cranked down the adjustment on the
calipers (C2s are a closed system and it allows that) until they were squeezing
the rotors pretty hard. Then I slipped shims in to the resulting spaces
between caliper and frame until no more would fit - and I *did* find a
substantial diff between the number of shims that filled up the front and rear
spaces - suggesting that the mounts weren't parallel (although I wouldn't be too
sure until I've ridden the thing for awhile...too many other variables....)

Also, the fact that my skewers used to fit perfectly when installing/removing
the rear wheel and now I have to loosen them a few turns when installing to work
with the slop between the drops and the hub suggests that something more than
just paing has gone goofey with that area.


--
PeteCresswell

Magura's tech support guy says to center the calipers WITHOUT the
pads. Line the rotor up with the parting line in the calipers. It is
much much easier to get them lined up that way.. using shims of
course, and possibly more shims on one side than the other.. whatever
it takes to get perfect alignment... NEVER touch the levers when doing
this.

Now put the pads in .. take a short ride to break them in.. then if
the gap is greater on one side then the other.. push the rotor against
the pad that is too close to the rotor and have someone hit the brake
handle... that will move the self adjusters just a little bit and that
usually equalizes the gap.

that's how i do mine.

charlie

"(Pete Cresswell)" wrote in message . ..

[snip]


Has anybody tried "yellow"...the sound like a step down from "green" in
durability...but I'm guessing each step down in durability carries some upside
in some other characteristic.

Dear Pete,

Earlier in this thread, you mentioned pads giving
you fits noise-wise and now I notice that you're
talking about different-colored pads and mentioning
yellow.

Deep in the bowels of the nearby thread about "6
or 8 inch rotor" brakes, Jobst Brandt is trying
to get brake basics through my thick head and
listed this link:

http://www.koolstop.com/brakes/#thinline

All the way at the bottom of this web page are
the various kinds of KoolStop pads, with their
colors and claimed qualities. The very last two
are weird-looking hybrids, with the front half
one color and the back half a different kind.

One hybrid pad is called the "Stinger" and has
a short yellow front section and a larger black
section and is supposed to help reduce noise.

I've asked Jobst what he thinks of this, guessing
that the answer is "not much," but he may surprise
me. Maybe the brand that you like is offering the
same sort of mixed-composition pads for noise
problems?

Carl Fogel

"(Pete Cresswell)" wrote in message
...
RE/
o have the
caliper mounts on the frame faced to ensure they are perpendicular

I think you've put me on to something with that. I looked more closely
at the
insides of the mounts. Ellsworth has coated that area with some very
heavy
plastic-like coating - much thicker than any paint I've ever seen.

Turns out the stuff is starting to peel off there - causing an irregular
surface
where the calipers and shims bear.

I trimmed it with a razor blade and then took a leaf out of the Avid book:
I
slackened the mounting screws a lot, then cranked down the adjustment on
the
calipers (C2s are a closed system and it allows that) until they were
squeezing
the rotors pretty hard. Then I slipped shims in to the resulting spaces
between caliper and frame until no more would fit - and I *did* find a
substantial diff between the number of shims that filled up the front and
rear
spaces - suggesting that the mounts weren't parallel (although I wouldn't
be too
sure until I've ridden the thing for awhile...too many other
variables....)

Also, the fact that my skewers used to fit perfectly when
installing/removing
the rear wheel and now I have to loosen them a few turns when installing
to work
with the slop between the drops and the hub suggests that something more
than
just paing has gone goofey with that area.


Possibly bent in a crash? I cacked my M1 seatstay strut so bad the rotor
rubbed on it. Had to get a replacement strut. But with Hope's type mount
it's pretty critical that they are parallel to the rotor. The Hayes caliper
mounts are slotted and allow the caliper some leeway. With those you just
loosen the bolts slightly, squeeze the lever and retighten the bolts.

Mike

RE/
Possibly bent in a crash?

I played around with shims a little more today. Turned out the "Avid approach"
wasn't such a good idea.

Now I've got the same number of .2 mil shims in the front and back bolts and it
seems like it's as good as it's going to get - verified by adding/subtracting a
few here and there.

The funny thing is that now when the brakes are applied, the portion of rotor in
front of the caliper is deflected inwards a little and the portion behind the
caliper is deflected outwards about the same amount. I *guess* it could be
some deformity in the triangle (it is, afterall, a little wider now than when
new) but the simplist explaination seems to be that the pads are cockeyed -
verified visually and with a micrometer. If that's the case, I'd expect them
to even out in a few hundred miles.... If not, maybe I'll blow a few hundred on
a new rear pivot arm - wouldn't want to be surprised like another poster with
the same make/model bike whose pivot arm just broke in half....
--
PeteCresswell