Followup Question: disc brake adjustment

I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble.
Easier to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is
rubbing a bit on the inside pad (Tektro IO brakes). "Ah," I thought,
"the very thing that I would need to fuss with if were I to try to swap
wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am
not seeing any kind of adjusting thingy (allen head, bolt head, lever,
pulley, hawser, valve, vernier, screwdriver slot) that looks obviously
like a "pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott

"Mike Rocket J Squirrel" wrote in message
...
I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble. Easier
to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is rubbing
a bit on the inside pad (Tektro IO brakes). "Ah," I thought, "the very
thing that I would need to fuss with if were I to try to swap wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am not
seeing any kind of adjusting thingy (allen head, bolt head, lever, pulley,
hawser, valve, vernier, screwdriver slot) that looks obviously like a
"pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott

You're not missing anything because no such adjuster is present. The
caliper is positioned correctly by use of various shimming washers and/or
facing the mounting lugs on the frame or fork. If the facing was never
done, your disc brake probably squeals like a scalded pig due to being
slightly out of the same plane as the rotor.

Cal

me wrote:
"Mike Rocket J Squirrel" wrote in message
...
I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble. Easier
to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is rubbing
a bit on the inside pad (Tektro IO brakes). "Ah," I thought, "the very
thing that I would need to fuss with if were I to try to swap wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am not
seeing any kind of adjusting thingy (allen head, bolt head, lever, pulley,
hawser, valve, vernier, screwdriver slot) that looks obviously like a
"pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott

You're not missing anything because no such adjuster is present. The
caliper is positioned correctly by use of various shimming washers and/or
facing the mounting lugs on the frame or fork. If the facing was never
done, your disc brake probably squeals like a scalded pig due to being
slightly out of the same plane as the rotor.


Thanks. This goes a long way toward explaining exactly why swapping
wheels on an MTB is not a casual task. It also reassures me to know that
I was not overlooking some obvious adjusting thingy. I'm not getting any
squeals -- the Tektro website makes some claim about the pads offering 3
degrees of self-adjustment for non-parallelism. Maybe that's helpful, I
don't know. So, does a fellow take his MTB back to the LBS from which he
bought it and ask them to shim this problem out, or what?

-- mike elliott

Thanks. This goes a long way toward explaining exactly why swapping
wheels on an MTB is not a casual task.
snip

As someone who hasn't yet converted to discs I am happy to learn
another reason/excuse not to upgrade or get a new bike. My LBS says
that once you've got 'em (discs), you don't go back. Supposedly, the
stopping power is *that* good and/or reliable. As a closet
weight-weenie, the extra weight of discs is another deterrent.

Stopping power with my V-brakes hasn't been an issue...in panic stops,
I find locking the (rear) wheel is far too easy. Do discs offer better
modulation? Will they prevent full lock-up in a panic situation?

aside I recently posted about a V-brake problem (this was actually on
my MIL's bike, my brakes work just fine). /aside

Do higher-end models of disc brakes offer easier adjustments? I swap
wheels out on a regular basis and don't require brake adjustment.
Re-tuning brakes after each wheel swap sounds like a real drag (no
issue for me with the V's). If I do eventually switch to discs, I
would gladly pay more $$ for ease-of-adjustment features. It drives me
nuts when a component requires constant adjustment under regular usage.

Cheers,
Dave

Mike Rocket J Squirrel wrote:
me wrote:
"Mike Rocket J Squirrel" wrote in message
...
I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble. Easier
to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is rubbing
a bit on the inside pad (Tektro IO brakes). "Ah," I thought, "the very
thing that I would need to fuss with if were I to try to swap wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am not
seeing any kind of adjusting thingy (allen head, bolt head, lever, pulley,
hawser, valve, vernier, screwdriver slot) that looks obviously like a
"pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott

You're not missing anything because no such adjuster is present. The
caliper is positioned correctly by use of various shimming washers and/or
facing the mounting lugs on the frame or fork. If the facing was never
done, your disc brake probably squeals like a scalded pig due to being
slightly out of the same plane as the rotor.


Thanks. This goes a long way toward explaining exactly why swapping
wheels on an MTB is not a casual task. It also reassures me to know that
I was not overlooking some obvious adjusting thingy. I'm not getting any
squeals -- the Tektro website makes some claim about the pads offering 3
degrees of self-adjustment for non-parallelism. Maybe that's helpful, I
don't know. So, does a fellow take his MTB back to the LBS from which he
bought it and ask them to shim this problem out, or what?

-- mike elliott

Remember that most discs and mechanicals particularly do not pull the
pads toward the rotor on each side. Normally, pushes one pad-rotor into
other pad-you stop, Rubbing of the pads on the rotor is very common.
Since you already have this bike, too bad you didn't opt for a vbrake
equipped one, with less hassle and probably better components all
around, instead of the expense and hassle of discs...

The bike shop ,may have somebody that understands discs, but most do
not...

Qui si parla Campagnolo wrote:
Mike Rocket J Squirrel wrote:
me wrote:
"Mike Rocket J Squirrel" wrote in message
...
I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble. Easier
to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is rubbing
a bit on the inside pad (Tektro IO brakes). "Ah," I thought, "the very
thing that I would need to fuss with if were I to try to swap wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am not
seeing any kind of adjusting thingy (allen head, bolt head, lever, pulley,
hawser, valve, vernier, screwdriver slot) that looks obviously like a
"pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott

You're not missing anything because no such adjuster is present. The
caliper is positioned correctly by use of various shimming washers and/or
facing the mounting lugs on the frame or fork. If the facing was never
done, your disc brake probably squeals like a scalded pig due to being
slightly out of the same plane as the rotor.


Thanks. This goes a long way toward explaining exactly why swapping
wheels on an MTB is not a casual task. It also reassures me to know that
I was not overlooking some obvious adjusting thingy. I'm not getting any
squeals -- the Tektro website makes some claim about the pads offering 3
degrees of self-adjustment for non-parallelism. Maybe that's helpful, I
don't know. So, does a fellow take his MTB back to the LBS from which he
bought it and ask them to shim this problem out, or what?

-- mike elliott

Remember that most discs and mechanicals particularly do not pull the
pads toward the rotor on each side. Normally, pushes one pad-rotor into
other pad-you stop, Rubbing of the pads on the rotor is very common.
Since you already have this bike, too bad you didn't opt for a vbrake
equipped one, with less hassle and probably better components all
around, instead of the expense and hassle of discs...

The bike shop ,may have somebody that understands discs, but most do
not...

I have Avid BB7 mechanical disc brakes on my cross bike, and they work
great. I can get the pads not to rub, and adjustment is a breeze with
the knurled knobs on the caliper. They came stock on a Cannondale
mid-fi bike I use primarily for a commuter. The problem on that bike
is not the brakes but rather is the hubs, which are OEM POS. I have
never, ever seen such a poorly made pair of hubs in my life -- the
bearings on right rear rusted in just a few months of riding in the
rain. I am going to have to build another set. Like someone said in
that Terry touring wheel thread, there are always a couple crappy
components on any prefab bike, but I am amazed at the number of
manufacturers that cut corners on bearings. You get a CF seat post and
crap hubs. Makes no sense. -- Jay Beattie.

Like someone said in
that Terry touring wheel thread, there are always a couple crappy
components on any prefab bike, but I am amazed at the number of
manufacturers that cut corners on bearings. You get a CF seat post and
crap hubs. Makes no sense. -- Jay Beattie.

Argggh. $800 mountain bike, shocked to find it was equipped with
absolute crap Chinhaur (sp?) bottom bracket. LBS proceeded to charge
me $35 for a shimano replacement. I doubt you'd find worse on a $100
Wal-Mart bicycle.

The manufacturers cut corners everywhere. Since I've started tooling
around I've noticed more and more 'issues', most recently the poor job
they've done on the cable housings (generally much too long). Maybe
it's just my experience...

On 8/11/2006 6:13 AM Qui si parla Campagnolo wrote:

Mike Rocket J Squirrel wrote:
me wrote:
"Mike Rocket J Squirrel" wrote in message
...
I asked yesterday about getting a second set of wheels for my new
entry-level MTB and it was pointed out that the hassle of adjusting the
disc brakes every time I swapped wheels was not worth the trouble. Easier
to simply change tires. Point taken.

I put the bike on my stand for routine poking and probing this afternoon
and noticed that -- speak of the devil -- the rear brake rotor is rubbing
a bit on the inside pad (Tektro IO brakes). "Ah," I thought, "the very
thing that I would need to fuss with if were I to try to swap wheels!"

So I took a look to see how to adjust things so the rotor was centered
between the pads. This should be simple. I'm not mechanically hopeless,
and have been working on my own bikes since I was a pup. And yet. I am not
seeing any kind of adjusting thingy (allen head, bolt head, lever, pulley,
hawser, valve, vernier, screwdriver slot) that looks obviously like a
"pads in, pads out" adjuster.

Um . . . some advice here?

-- mike elliott
You're not missing anything because no such adjuster is present. The
caliper is positioned correctly by use of various shimming washers and/or
facing the mounting lugs on the frame or fork. If the facing was never
done, your disc brake probably squeals like a scalded pig due to being
slightly out of the same plane as the rotor.

Thanks. This goes a long way toward explaining exactly why swapping
wheels on an MTB is not a casual task. It also reassures me to know that
I was not overlooking some obvious adjusting thingy. I'm not getting any
squeals -- the Tektro website makes some claim about the pads offering 3
degrees of self-adjustment for non-parallelism. Maybe that's helpful, I
don't know. So, does a fellow take his MTB back to the LBS from which he
bought it and ask them to shim this problem out, or what?

-- mike elliott

Remember that most discs and mechanicals particularly do not pull the
pads toward the rotor on each side. Normally, pushes one pad-rotor into
other pad-you stop, Rubbing of the pads on the rotor is very common.
Since you already have this bike, too bad you didn't opt for a vbrake
equipped one, with less hassle and probably better components all
around, instead of the expense and hassle of discs...

The bike shop ,may have somebody that understands discs, but most do
not...


Well, yeah -- I got the bike without doing any research. My bad, and I
have to deal with it.

So, anyways, I gather that the whole caliper housing needs to be moved
inward or outward, as needed, so the pads will clear the rotor. On a
road bike, any rubbing of brake pads on the rim is something not to be
tolerated, and it is easily dealt with, thus my immediate concern and
inquiry. But MTB's with disc brakes normally have some rubbing? Probably
a trivial amount of drag compared with the other conditions a MTB has to
deal with.

If a fellow wants to get all obsessive about it, moving the caliper
inward appears to be fairly straightforward by using shims, as has been
pointed out earlier in this thread. However, I have the more exciting
situation where I need to move my caliper outward. I can't seem to find
shimming washers in negative thicknesses, so I need to remove some
material, either from the caliper's mounting surface, or the mounting
surface on the dropout. 20 mils looks like it should do the job, but I
have files, no end mills or real facing equipment.

(Though I do have a friend who fabricates parts for the aviation
industry at our local community airport . . . I bet he could do it.)

Or I could not worry about it. After all, the plan is to use the bike to
poke along dirt roads and easy trails. My doctor would kill me if I
tried anything that could toss me off the bike. One big fall and this
metal rod inserted up my femur to which my ti knee is attached to could
twist right out. Maybe this additional drag is a Good Thing.

-- mike elliott, learning something new every day.

Discs are fantastic in every way........control and modulation is fantastic
the power is unbelievable.
I have used discs and Vs (and cantis) and will never return to Vs on my
mountain bike.

They need no maintainance at all - see bleeding tip below, pads last ages.
Wheels dont need to be kept dead true and you can keep riding after crude on
trail straightening.

They are far more cost effective than rim brakes - ie V pads wear out
quickly, I have done a pair in a days wet gritty riding £7 a time BUT they
also wear the rim this costs £30 a time ($50) two winters for rear wheels
four for fronts was all I used to get.
Hope minis cost me £100 a wheel and I have saved more than that in their 4
years use by not rebuilding wheels and not buying new V pads every few
weeks.

I have 2 bikes with Hope minis / hope XC hubs, the wheels are totally
interchangable - no adjustment no binding.
Note that Cannondale sold a MB with a spare set of 700C wheels for road
use - disc obviously and interchangable.

Setting up with the shimms does not take long but get your LBS to fit them
when you buy them if your not sure, mine did it free 30 mins whilst I
waited.

Also top tip.....this really works.
To bleed your disc brakes add a couple of zip ties to pull the levers back
to the bars - brakes dont need to be on that tight, the braking circuit just
needs to be active. Then put your bike on your car rack (must be upright in
normal riding position) then drive to your favourite trail.....50 miles
works, but shorter trips may be OK. The vibration shakes all the air up to
the resevoir -I assume. That spongey brake feel will be gone when you get to
the ride.
Try it.....I have never bled my brakes in the conventional way.
The only maintainance Ive done is new pads and I sometimes lightly stone the
disc to break up the surface, oh and dont get oil on them.....

Max
Top UK ride Forest of Ae Scotland

Unfortunately this newsgroup seems to focus on road bikes and claim such a
common current MTB equipment as disc brakes, suspension forks etc. as
unnecessary gadgets. While discs aren't necessary for everyone they do
provide consistent braking power in foulest weather.
You can get pretty good information on places like mtbr.com (discussions are
active and plenty of helpful people there) and it's Disc Brake FAQ
http://www.mtbr.com/techtalks/brakes/brakesfaq.shtml is good solid
information.

Now quick answers to current thread and the previous one:
- disc wheelsets are fairly compatible with each other even if disc hubs
might have slightly different dimensions the most typical rotors with 6 bolt
attachments can be shimmed with Syntace disc shim (0.2mm thin shims) or by
separate shims to have similar offset to hub.
Relatively inexpensive disc wheelsets (Shimano Deore hubs) are available
from most places.
- rubbing discs can be solved with caliper/pad adjustment (mechanical brakes
such as Avids), resetting pistons on hydraulic ones or by facing disc tabs
on forks with tools from Hope, Magura or Park. While such tools are quite
expensive (150-200$) the operation is simple to do at competent LBS and some
smaller online companies do rent them for a smallish fee. Most current
suspension forks do require facing for proper brake installation, there is
just too much paint on the disc tabs preventing correct alignment without
facing. This will help many brakes that squeal too.

Hope this helps,
Marko