Re: drilled rotors and cooling

["Tony Sims" <simstony@domain.elided>]

Joe writes:

>I brake into the turns very late, and had problems with fade, incrementally
>alleviated by fitting AXXIS semi-metallic pads and 600F degree brake
>fluid.  The situation had gone from virtually no brakes after the second
>session of the day, to "I wish these were a lot better, but I'll probably
>make it or spin."
>
>The rotors I fitted were stock, drilled by a local machine shop.  They make
>a katydid buzz when I put them on, but I ran seven sessions with very
>little fade.  They are a very definite improvement; I leave it to you to
>surmise why.

A little more data mined from the blunders file (buried in a lotta fluff
'cause I ain't workin' again and I have too much time on my hands) --
My ' 74 GTV wears drilled rotors all around, installed by some PO.  Since
they're in fine shape, I've not replaced them.  The soft lines are candidates
for replacement as I have no idea of their age.  The improvement SS lines made
on my '70 BMW demands the same for the Alfa, so that's a future project.  Even
for a vacuum-assisted system, the brakes on this car have always felt pretty
solid, and I've been over the bottom of the car and no damage or leaks are
evident in any of the soft or hard lines or the calipers.  With the AROO track
day on the horizon, I had been planning to pull the pads to see what they were
and what shape they were in, and to replace the brake fluid.  Still, several
weeks back this task was not yet complete when I headed out to meet some
friends for a round of golf on a warm Friday afternoon.

I'll skip all the details of why, but road construction caused me to be
separated from the group, and I found myself needing to make up a lot of time
to avoid missing the tee-off.  The course is near my childhood home, out in
the sticks west of Portland, so I know some shortcuts and I took off on one.
One particular stretch of this rural bypass is a series of 1-plus mile
straights with double 90-degree jogs that are marked at 15 MPH (section line
roads).  It's flat, clear farmland and I know the roads, so I was pressing
hard (my speedo runs out of interest at 65 MPH, but 6,000 RPM in 5th must be
close to triple digits).

I've not pushed the car this hard since I bought it, prior to last winter
because of the unknown condition of the engine, and not until now to get the
new rebuild well broken in.  At the first set of "chicanes", I had plenty of
brakes and no concerns.  At the second set, I noticed a little softness.  At
the third, I was giving thanks to Sta. Giulietta that flat wheatfields make
for a good runoff...  I did make the turns, ragged and tailwagging and
grateful for 60 series rubber, but for the remainder of the trip my braking
points were recalled from my truck driving days and I stayed in the functional
range of the speedo.

On Saturday morning, the car was up on stands, the pads came out, and fresh
charge of Ate Blue was pumped through the lines.  The soft lines showed no
evidence of cracking or swelling.  The pads are in acceptable shape, but of
indeterminate make.  They went back in for now, but will be replaced before
any track day fun.  I took the car for a drive to a place I could do some hard
braking, and gave it a run.  The improvement was, as they say, night and day.

Never having driven this car with any but drilled rotors, I can't speak to any
difference they make (save that katydid buzz Joe mentions).  However, let the
record show that fresh brake fluid is not just pretty, tasty and good for
stripping paint, but is critical to proper braking performance, and without it
all the stop-faster gear on earth isn't gonna help...

Tony
Portland, OR
74 GTV 2000
70 2800 CS
72 Badvaria
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