From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Side-pull brakes need toe-in?
Date: 15 Apr 1998 00:33:30 GMT

Dimitri Nikas writes:

> Is it true that side pull brakes such as the Shimano Ultegra and
> Dura Ace do not need toe-in?  Forgive the inexperience.  As always
> any insight is greatly appreciated.

I'm not convinced that any brake needs toe-in.  I never do that to my
brakes and I suspect the practice may come from a non-correlation
between cause and effect.  Because the center of pressure of most
brakes is not in the center of the pad (because there is a torque
about the mounting bolt), brakes normally wear-in with a bit of toe-in
if you do nothing to them.  Because new brake pads often squeal and
used (toed-in) pads do not, it is assumed that the toe-in is the
answer.  I find that the skin of the pad has gummy stuff that excites
squealing and that when worn off, either by riding in the rain or
watering the pad while braking down a descent, the pads become
silent.

If I had bent my 1970's Campagnolo calipers as I have seen bike shops
do. they would long ago have broken off.  I use KoolStop red generic
bolt pads and have no problem with them squealing unless I ride
through lush green grass that has waxy blades.  Watering the brakes
while braking or braking while riding through a conveniently long mud
puddle usually does the trick.  In the worst case, put some kitchen
cleanser on the wet rim and ride while braking.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Side-pull brakes need toe-in?
Date: 15 Apr 1998 23:11:08 GMT

Frank Krygowski writes:

>> OK, let's assume you did that.  If your brakes wear, then either
>> the toe-in you induced will go away, or you continually re-adjust
>> the pads, or natural wear has toe-in as I described and has no
>> effect on the squeal.  How do you explain that scenario or that
>> others are able to do this without adjusting the brake pads?

> The toe-in I induced _does_ go away.  When my brakes become worn, I
> find that I must indeed re-adjust to restore toe-in to eliminate
> squealing.  I generally do this by resetting the position of the
> brake shoes, but in some cases I've done it by sanding the brake
> shoe with a disk sander, as another poster mentioned.

That means that finally the brake pad is worn off in a steep angle so
that the leading edge is worn out while the rear is still nearly like
new.  My point is that brake pads naturally wear off to produce
toe-in, even if they are mounted parallel to the rim, because all
brake mechanisms have some elasticity and play.  This compliance means
that the pad will make harder conmtact at the rear than the front from
the forward drag of the pad on the rim.  This causes wear so that on
application the leading edge of the pad will contact first.

> This has happened to me enough times over the past 20+ years that
> there is no doubt (in my mind, anyway) about the cause and effect
> relationship.  Brakes squeal.  I adjust toe in (and usually, nothing
> else).  Squeal stops.  In fact, the rear brake on my touring bike
> has just started squealing, so I'm about to do it yet again.

I don't understand how you lose toe-in unless you have more toe-in
than one normally uses.

> BTW, the last set of pads I bought have mounting studs which are
> offset.  Perhaps these will wear in such a way that toe-in is
> maintained.  It would be nice.

Toe-in cannot be maintained by such a pad because it prefers to wear
parallel.  Natural toe-in is inherent to any commercially available
brake caliper.  Using an off center anchor bolt perverts that effect.

Jobst Brandt      <jbrandt@hpl.hp.com>