Getting Canti Brakes Even?

I just reverted my early-80's StumpJumper to it's original canti
brakes in the rear - but I can't seem to get the pads even close
to the same distance from the rim.

Assuming the rim is centered, is there some trick to doing this?

I fooled around with the pad positions, but suspect I'm missing
something else.

Or are they just inherently not very precise in that respect?
--
PeteCresswell

"(PeteCresswell)" wrote in message
news
I just reverted my early-80's StumpJumper to it's original canti
brakes in the rear - but I can't seem to get the pads even close
to the same distance from the rim.

Assuming the rim is centered, is there some trick to doing this?

I fooled around with the pad positions, but suspect I'm missing
something else.

Isn't this the normal thing where the spring has three holes to go into on
the post, and there's a screw adjuster for fine tuning?

PeteCresswell wrote:

I just reverted my early-80's StumpJumper to it's original canti
brakes in the rear - but I can't seem to get the pads even close
to the same distance from the rim.

Assuming the rim is centered, is there some trick to doing this?

I fooled around with the pad positions, but suspect I'm missing
something else.

Or are they just inherently not very precise in that respect?

There are three adjustments that matter. First and coarsest is
choosing which of the three available anchor holes in the frame boss
to use for the springs. Usually the right choice is the middle hole
of each boss, but sometimes you need more or less spring tension, or
the sides differ enough to warrant using different spring positions.

Second order of business is to use the fine adjustment screws (like on
a Shimano canti) or spring preload wrench flats (like on a self-
energizing canti) to get you centered. If you don't have either of
these means available, you'll have to gently and carefully bend the
springs until you get the results you want. To do this, you might
have to loosen the pad holder so that the arm can be forced far enough
to set the spring.

The main thing that will discombobulate your brakes on a day-to-day
basis is the straddle hanger moving along the straddle. Shove it to
the center and keep it there. You can pinch the straddle hanger onto
the cable a bit to keep it from migrating. Tune with the fine
adjusters as necessary to make the brakes center when the straddle
hanger is centered.

Chalo

Per Chalo:
Second order of business is to use the fine adjustment screws (like on
a Shimano canti) or spring preload wrench flats (like on a self-
energizing canti) to get you centered. If you don't have either of
these means available, you'll have to gently and carefully bend the
springs until you get the results you want. To do this, you might
have to loosen the pad holder so that the arm can be forced far enough
to set the spring.

The main thing that will discombobulate your brakes on a day-to-day
basis is the straddle hanger moving along the straddle.

My money's on the straddle cable.

No fine adjustment screws or additional spring holes on this
puppy.

But the straddle cable is riding on the fender - which can't be
doing things any good. If I can find another straddle cable, I
can try it longer - hopefully long enough so it clears the
fender.

But meanwhile, it seems like braking pressure is equalized by the
straddle cable/hanger so there doesn't seem tb any harm done
beyond extra brake play as long as neither pad rubs.
--
PeteCresswell

On Jun 12, 4:35*pm, "(PeteCresswell)" wrote:
Per Chalo:

Second order of business is to use the fine adjustment screws (like on
a Shimano canti) or spring preload wrench flats (like on a self-
energizing canti) to get you centered. *If you don't have either of
these means available, you'll have to gently and carefully bend the
springs until you get the results you want. *To do this, you might
have to loosen the pad holder so that the arm can be forced far enough
to set the spring.

The main thing that will discombobulate your brakes on a day-to-day
basis is the straddle hanger moving along the straddle. *

My money's on the straddle cable.

No fine adjustment screws or additional spring holes on this
puppy.

But the straddle cable is riding on the fender - which can't be
doing things any good. * If I can find another straddle cable, I
can try it longer - hopefully long enough so it clears the
fender.

But meanwhile, it seems like braking pressure is equalized by the
straddle cable/hanger so there doesn't seem tb any harm done
beyond extra brake play as long as neither pad rubs.

And make sure the bosses are rust free, clean and lubricated.
Sometimes lack of lubrication results in the brakes not centering. --
Jay Beattie.

PeteCresswell wrote:

Per Chalo:

Second order of business is to use the fine adjustment screws (like on
a Shimano canti) or spring preload wrench flats (like on a self-
energizing canti) to get you centered. *If you don't have either of
these means available, you'll have to gently and carefully bend the
springs until you get the results you want. *To do this, you might
have to loosen the pad holder so that the arm can be forced far enough
to set the spring.

The main thing that will discombobulate your brakes on a day-to-day
basis is the straddle hanger moving along the straddle. *

My money's on the straddle cable.

No fine adjustment screws or additional spring holes on this
puppy.

Well, you can still force the spring (a time-honored if inelegant
method). But like I said, you may have to loosen or remove the pads
to get enough range of motion for that maneuver.

But the straddle cable is riding on the fender - which can't be
doing things any good. *

That's probably your issue.

Chalo

I didn't see any talk of the spacers/washers.

If one side is a mile away ... and all else is even and well ...
perhaps Pete should invoke/manipulate spacers?

(PeteCresswell) wrote:
Per Chalo:
Second order of business is to use the fine adjustment screws (like on
a Shimano canti) or spring preload wrench flats (like on a self-
energizing canti) to get you centered. If you don't have either of
these means available, you'll have to gently and carefully bend the
springs until you get the results you want. To do this, you might
have to loosen the pad holder so that the arm can be forced far enough
to set the spring.

The main thing that will discombobulate your brakes on a day-to-day
basis is the straddle hanger moving along the straddle.

My money's on the straddle cable.

No fine adjustment screws or additional spring holes on this
puppy.

But the straddle cable is riding on the fender - which can't be
doing things any good. If I can find another straddle cable, I
can try it longer - hopefully long enough so it clears the
fender.

But meanwhile, it seems like braking pressure is equalized by the
straddle cable/hanger so there doesn't seem tb any harm done
beyond extra brake play as long as neither pad rubs.

once both pads contact, pressure is always equalized because both force
reactions need to be in equilibrium.

Neil Brooks wrote:

I didn't see any talk of the spacers/washers.

If one side is a mile away ... and all else is even and well ...
perhaps Pete should invoke/manipulate spacers?

Old canti brakes don't use spacers. They have smooth brake pad posts
that are slid to the appropriate position in their holders before
being cinched down.

Chalo

Neil Brooks wrote:
I didn't see any talk of the spacers/washers.
If one side is a mile away ... and all else is even and well ...
perhaps Pete should invoke/manipulate spacers?

The normal path is:
Center wheel in bicycle
Double check that the rim is indeed centered
Center brake
Ride

Spacers (asymmetric left to right) are not normally used

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971