From: "Carl Buckland" <buckland_at_mail.xmission.com>
Date: Sat, 4 Jul 1998 09:32:12 +0000
Subject: Avoiding Rotor Warpage (long)
From: John Swapceinski JSwapceinski_at_sisaro.samsung.com>
To: "'buckland_at_xmission.com'" <buckland_at_xmission.com>
Date: Tue, 30 Jun 1998 14:05:22 -0400
Any way you know of to avoid frt rotor warpage during track use?
Yes, kind of like I know how to avoid getting speeding tickets.
Sometimes it works, sometimes it doesn't. Unfortunately, I
have failed at both (avoiding tickets and warped rotors) far
too many times, but here are a few hints:
- break in your rotors for 500 miles before tracking. This is
*very* important. Tempering the rotors is something that has
sort of been forgotten lately, but was brought back to me
recently as I was
ordering my 5th set of rotors for this year. My "son" Todd
drives to and from the track, and has been getting a lot more
out of his rotors than I have (he drives the 800 miles, whereas
I trailer). I think that there is a connection. I have heard of
some racers putting their rotors in the oven for tempering, but
I have not yet tried that. I will, however, and think that 150
degs for 1 hour, than 200 for 15 minutes might be just right.
Caveat: this is my Mr. Hyde side talking. Try at your own risk!
- If using race pads (recommended, I use PF 90's), use them
ON THE FREEWAY (not town; they will gouge your rotors until
they are warmed up) for a hundred or more miles before
tracking. It will coat your rotors with pad material which will
keep them smooth and free of shutter.
2a) In lieu of this, keep an extra set of rotors, designated
solely for use with your race pads. I try to have a set of
rotors for each set of specific pads (street, autocross, track).
3) rotors: stock is fine, floaters help only a little, in my
experience. Stock knock-offs from Brembo cost about
$120/set of fronts (BMP and others), whereas OE BMW rotors
cost $250 to $300. Floaters cost even more. I use up rotors
like gas and oil, now that they are so cheap. I wouldn't go too
crazy over a set of warped rotors. At $300/set, I was much
more worried about longevity.
4) brake lines and fluid: not necessarily related to rotor
warpage, but I do recommend using stainless brake lines, and
a good racing brake fluid. I use ATE Super Blue.
5) ducting: try the Donahue brake ducting method that I list
6) warm up your rotors, pads, fluids and yourself SLOWLY.
Brake gently, "squeeze" on the pedal, squeeze off. *Work up*
to throwing the anchor overboard. There is a place for
all-at-once braking, but even then, do it smoooothly.
7) let every second or third lap be a cool-off; you don't have
to go 10/10's every lap. Moreover, there is always a chance
to cool things off; you get behind a slow car, and know that
you can't pass him for 2 or 3 turns. Back off a little, slow
down, let things mellow, and wait until your passing zone
comes. Then get back on his bumper
to let him know you are there, and resume your quest for the
next guy down the track.
and finally.......8) read 3 again. Worrying too much about
making one set of rotors last the whole year is
working rotors warp, period. I think that these hints will help
prolong their life, however.
Here is the Donahue brake ducting method, with some extra
notes from me:
remove the ducts. Tape over the opening into the wheel well.
Cut away the lower inside wheel well shroud near were this
hole is. Use
34" (3' is slightly too long) of 2 1/2" duct hose (again from
Pegasus; I use the medium expensive stuff, something like
3" is too large (3" worked beautifully on the 2002, but there's
more room in the wheel wells). Connect the hose to the
cutback duct (it sort of threads right into the rear part of the
duct), through the hole you've cut (I squeeze it into an oval
shape at this point) and use a tie strap to tie it to the drag
strut. The important point, and the hard part, is to lead it so
that it clears the wheel at full lock-it is possible, but takes a
little bit of effort. For the final
connection, it's best to remove the wheel, and rotor. Cut
away the inner part of the brake shield (I used several radial
slots, and rolled the metal back) so that the ducting will fit in
(make it a tight fit), and put a hose clamp around the
cutaway parts of the shield to help hold the ducting in.
Another hose clamp around the strut and ducting might help.
If you get the ducting a couple of inches away from the inside
of the rotor, this will give the best effect. I tested the
performance and optimum fit by using a leaf blower into the
duct at the front. I then fiddled with how and how far the
ducting went into the lower strut/cutaway shield until the air
coming out of the reinstalled rotor seemed to maximize.
After it's all together, it's good for most of a year in my case,
before the ducting starts to wear out and has to be replaced.
You can always keep it going longer with applications of duct
tape. Clearly, it would be even better to use the fog lamp
openings-they are larger and not needed anyway. I decided to
go the route above because it was easier. It was easier to
remove the factory ducts, and easier to adapt a duct into this
opening. Furthermore, it would be harder leading the ducting
from the fog lamp. In any case, I will probably try to do this
sometime in the future. (Similarly, I'm looking at removing the
left side headlight assembly to give improved cool air flow to
the air cleaner.)
I hope that the above isn't too confusing (seeing my car
would make it so much clearer); I'd be happy to answer any
I followed up with.....
I have some trouble visualizing this:
" Tape over the opening into the wheel well. Cut away the
lower inside wheel well shroud near were this hole is. "
It is because the new hole in the shroud is in a different place
than the original hole where the duct exited. The new hole is
larger, and more inboard than the original hole. Why do you
remove the original duct?
It is because the 2 1/2" hose is larger than the duct.
You then say:
"Connect the hose to the cutback duct"
I thought that you *removed* the duct. Do you mean "the
hole in the cut out shroud"?
Then you say:
" and use a tie strap to tie it to the drag strut."
He means to the strut.
Finally, you suggest:
" Cut away the inner part of the brake shield (I used several
radial slots, and
rolled the metal back) so that the ducting will fit in (make it a
tight fit), and put a hose clamp around the cutaway parts of
shield to help hold the ducting in. Another hose clamp around
the strut and ducting might help. If you get the ducting a
couple of inches away from the inside of the rotor, this will
give the best effect."
For better cooling, I have already removed the brake shields.
Are they necessary to holding in the duct hose? My guess is
they are *integral* to the design, and are the only thing that
CAN hold in the duct hose. If this is the case, the question
becomes, "Is it better to add ducting, which ties into the
shields, or is it better to remove the shields?"
Carl talking: Leave the brake shields on. They are not easy to
remove, as they involve removing the wheel bearing, and they
to hold the ducting in place. Also, I think that the shields can
be bent inward, which helps bring more air into the hub. If you
don't or can't place some duct hoses, then I would recommend
removing the shields. There is also the downside that they are
there for a reason; to keep debris off and out of your brakes.
I bought all of the stuff that I needed from Racer Wholesale
for about $104. Parts are: SPA-D109 air duct 13.95
adapter 3" to 21/2" 11.95 x 2 THE-SS250 11 ft (only size
avail) of 2 1/2" silicone hose 49.28. Silicone is probably not
necessary, but it could get hot at the hub Racer Wholesale:
Good luck, and let us know how it worked out,
Racer Wholesale 1-800-886-RACE
SPA-D109 air duct = 13.95
SPA-D103A hose adapter 3" to 2-1/2" 11.95 x 2 = $23.90
THE-SS250 11 ft (only size avail) of 2 1/2" silicone hose = 49.28
total cost $104.
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