Re: Wet Brakes

[Scott Fisher <sfisher71@domain.elided>]

--- Dave Martin <dwmartin@domain.elided> wrote:

[problems with cold braking performance deleted]

Dave, 

You're correct in assuming your car shouldn't act like
this.  Neither of my Alfas does, and while the Berlina
is getting a full brake job in the very near future to
replace all the hydraulics as well as all the friction
materials, even IT doesn't do what you describe -- and
I get a lot of exposure to wet braking here in
Portland, Oregon.

> This happens "everytime" now, but I've had the car
> for about 11 years and I do not recall that this 
> happened when I first owned it  - maybe it did and I
> just don't remember.  Anyway, it surely happens now
> everytime it rains.

Diagnosis 101: When an area of performance changes,
don't start by asking what NEW component you can
introduce -- look at what OLD components may have
deteriorated or may have been altered through some
other means.  

So: What else has changed in your Spider in the
interim?  Wheels, tires, brake pads, etc.?  

Brakes are not only a critical safety system, they're
also designed to wear out in the performance of their
duties.  While every moving part of your car
experiences some wear during normal operation, the
brakes are "supposed," in a way, to grind themselves
down to dust over time, at which point you replace the
worn components.

Have you already checked the pad thickness?  And when
was the last time you replaced the pads?  

> I see in IAP's catalog that for the upgrade
> (cross-drilled and slotted)
> rotors, that they say "...and improve wet-weather
> braking."  Is this what I need?

Did your car have those when it was working well? 
That's the question to be asking -- what has changed
since it worked well?

Here's how you can get a clue where to start: Remove
one of the front wheels.  Look at the pads, either
from above or from the rectangular opening at the back
of the caliper -- you're looking at their thickness. 
You should see two distinct strata on the pads (though
they're probably covered by reddish-brown dust). 
Farthest from the rotor, you should see a 1/8" thick
stratum -- that's the pad backing plate, which is made
of metal and is a very BAD friction material, but a
fairly GOOD machining tool.  

Right up next to the rotor, you should see another
stratum.  That is the friction material -- the stuff
that makes the brake pad work.  And it's the part
that's designed to wear down over time.  How thick is
it?  If you can't see it at all, it means your brake
pads have worn out completely and are about to chew up
your rotors (if in fact they haven't already started).
 Usually this is accompanied by loud scraping noises
and a dramatic loss of braking efficiency under all
conditions, so you would probably have noticed before
now.

But it's been my experience that, for whatever reason,
if the friction material has worn down to a thickness
much less than 1/4", simply replacing the brake pads
will bring about an improvement in braking
performance.  I'm not entirely sure why, but new pads
(once they're "bedded in" -- see below) seem to work
better than old.

"Bedding in" refers to the initial few miles of
operation for new brake materials.  For several
reasons, you get the best long-term performance out of
brakes if you follow the pad manufacturer's
recommendations for bedding in new pads.  The box
should have them, but they're typically simple: drive
at 35 mph in a safe area and make a few slow stops
with no more than half pressure.  (The first stop WILL
be scary because the pads aren't working properly
yet.)  Then gradually bring up the speed and the
pressure till you're stopping from highway speeds with
hard pedal pressure (again, do this someplace where
you can safely do so).  

Finally: when was the last time you replaced your
brake fluid?  Alfa used to require this every year;
most manufacturers today suggest every two years. 
Most brake fluids absorb moisture, which could be
contributing to your problems in the rain. 

In short: while slotted/drilled rotors MIGHT help,
they're almost certainly not the problem if only
because your car didn't have them when it used to work
well.  Start by putting the braking system right,
really right, before you start modifying it.  I've
priced out the bits for a full brake rebuild from "the
usual sources" in preparation for doing this to the
Berlina, and it's only about $250 for EVERYTHING --
caliper rebuild kits, new brake hoses, new pads, even
a new master cylinder (under $90).  The new master is
probably overkill for your situation, but I'm taking
no chances with the Berlina, I'm replacing everything
all at once.

The one thing, interestingly enough, that I'm NOT
ordering for the Berlina in preparation for a complete
brake job: rotors.  Draw your own conclusion, and, as
John Hertzman says, enjoy yours...

--Scott Fisher
  Tualatin, Oregon
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