BRAKE
COOLING
a Fox Body Mustang
Article 1
My
Mustang has just recently undergone two complete brake iterations, each more extreme than the
last.
Stock Fox Brakes and 2300-K Cobra Brakes
Like most Fox-body Mustang owners, I started out with 11" single piston brakes in front, and drums
in back. Yuck. This set-up was not strong enough to survive even a short street-tire session at
Waterford, which is easy on brakes. In fact, my second outing with the car I went off track twice,
both of which I attribute to the brakes!! These "agricultural sessions" were after I went to good pads
front & rear, stainless steel guide bushings to replace the rubber ones, stainless steel lines, and cut
away the brake shields for improved cooling.
I knew the set-up would never last on wide sticky rubber, so I went about putting together what
amounted to a Ford Motorsport 2300-K kit. This kit uses the brake set-up that was first introduced on the 1993 Cobra R. It uses a 2 piston PBR caliper in front
(38mm piston diameter) on a 13" vented rotor. On the back, it uses a single piston Varga caliper on an 11.65" vented rotor. Suddenly when I used that middle
"whoa" pedal, the car STOPPED. This is nice.
Brake Cooling, Chapter I
Then I went about adding some brake cooling. I knew that I wanted at least a 3" duct
going to each rotor. This was not a Trans-Am or Winston Cup car, so I did not need the
set-ups like some race cars use. (WC cars often run THREE 3" ducts to each side.
Man, that's cooling!) But as it happened, I got the parts from the same place. The
Roush garage in Livonia, Michigan proved to be just the ticket. If you knock on the door
and ask nicely, they'll show you the "attic", where old parts are stored. Everything up
there is for sale, from Carbon Fiber SN-95 body panels, to Alcon 8 piston calipers, to
WC motors. :) I found myself two backing plates that were used on the Craftsman
Super Trucks, some double wall silicone tubing, and two high volume marine fans that
were also used for brake cooling. Sure the stuff has been used, but I got out of there for
about $100!! Can't beat that.
Unfortunately, a great idea became a pain as I found that the SN-95 spindle forced the
backing plate outlet in a poor direction. The hose, under large steering angles, would get
caught between the sway bar and the wheel, and it quickly damaged the hose.
under the "Chapter II" heading, of the newer ducts & spindles, and notice the large black wear spot, where the tires damaged the hose. The hose has
since been replaced on both sides.)
Here is a picture of the brake blower install on the passenger side of the car. Note that the fog
light brackets and front fascia support have been removed for weight savings. Slipped over the
fog light opening is a 6" to 4" galvanized steel reduced found at a hardware store. I had to slightly
notch the fiberglass bumper so that the reducer would fit in place, but the fit was so good that it is
not fastened on! Don't notch the bumper too much, and like me, your bumper can serve to hold
the reducer in place.
Attached to the reducer is the blower. Since the ID/OD dimensions of the blower and reducer
were the same, neither would fit inside the other. My solution was to place them end to end, so
that they were as aligned as I could get them, and use 200mph tape to tape them together. This,
like the fit of the reducer, was a kludge that was meant to be temporary, but it has held up
amazingly, and I have no plans on changing it unless there is SOME sign of failure.
Note that the blowers were hooked up to the 12v leads for the fog lights, and they operate using
the fog light switch. I simply spliced the connectors off my broken fog lights onto the blowers,
and then plugged them right in.
This picture was taken before fitment of the Cobra R wheels, which required extensive front fender extension modification, which is described below.
The Brembos
I recently decided to make the move to Brembo brakes. These are a four piston caliper
which bolt directly to the spindle. The caliper is actually a modified Viper Caliper. It
uses the same outer half, and a slightly different inner half to accommodate the different
spindle. I understood that I could re-use every other part of the braking system, right
down to the stainless steel lines and the rotors. Or so I thought. The conversion became
much more intricate and expensive than I originally planned, but the rewards were worth
the effort, without a doubt.
The Brembos are truly a beautiful, beefy, and well designed brake system. The Galpher
pads can be changed without ever removing the caliper from it's mount on the spindle.
There are dual bleeders on each side, to be sure that each part of the caliper is
completely free from air. The caliper uses a staggered piston design, with a 36mm and
40mm piston on each side of a fixed caliper. This four piston scheme ends up preserving
the hydraulic ratio of the PBR calipers almost exactly, with their twin 38mm pistons. The
staggered bore design eliminates longitudinal tapered pad wear, greatly extending pad
life. This more even clamping force on the rotor also serves to extend rotor life, a factor
which is compounded by the use of longer-lasting 99 Cobra rotors to start with. The Brembos are also far stiffer than the PBR calipers, eliminating radial tapered
pad wear, extending durability under hard use, and improving pedal feel. And the things just look beautiful.
Wheel Fitment, Chapter I
The first snag came in the fact that neither of my wheel sets would work on the car. I had a set of 94 Cobra wheels for my street tires, and a set of black Ronals for
my track tires. Neither would clear the caliper, even using a small spacer. (Many people have heard me yell and scream about how much I HATE the idea of using
a spacer. I have, and continue to avoid their use at all costs.) This snag dictated my purchase of another set of wheels. And the only 17" wheel that I could find that
would fit the massive Brembos: The 1995 Cobra R wheel. I had generally been avoiding this wheel up until now. I have yet to hear of anyone just bolting them on to
a Fox body car without SOME complications, such as wheel / tire clearance issues. And then there is the fact that EVERYONE runs them on the track. Any
SAAC-MCR event will reveal numerous people running them. Sure they are cheap and effective, but they were getting rather bland in my eyes. But I decided on
them nonetheless. They were light, strong, cheap, and available on short notice. And on top of that, they will readily support a 275, where my previous rims, being
17"x8", would barely support a 255 tire.
Brake Cooling, Chapter II
The second snag came when I started working out the brake ducting set-up. I
would re-use the ducts, fans, and general hose routing, but replace the troublesome
aluminum backing pates with Carbon Fiber pieces. When I mocked everything up,
I found that, despite the backing plates being designed for the SN-95 spindle, they
did not fit in the area of the steering arm. A little research turned up the fact that
the spindle had been changed in 1996, with the new spindle have a lower steering
arm (for better bumpsteer, especially on lowered cars), and being 8mm wider (for
a total of 16mm more front track than the 94-95 spindles). I acquired a set of
these, and transferred these onto the car. The ducts now fit, aside of some
clearance issues with the rotors which were dealt with using a small hand file
(anything larger risked cracking the Carbon Fiber). Okay, one problem dealt
with. Along with these wider spindles came the need to lengthen the tie-rods to
counter the massive toe-in which occurred after this spindle change.
Wheel Fitment, Chapter II
Now that I had the brakes, spindles, and ducting in place, I could finally start test fitting the wheels on the car. Keep in mind that I had never had these wheels on my
car. I only had the knowledge that several SN-95 cars ran the Brembo/Cobra R wheel combo with success.
Fitting the Cobra R wheels to the Fox chassis is more than just a slight challenge,
especially with my complications. The Cobra R wheel comes in two different offsets,
24mm and 36mm. The original Cobra R wheel, the R58, has a 24mm backspacing
which is good for all four corners of an SN-95 car. The R58 also fits well in front of a
Fox body car that has the Cobra brake upgrade. But the rear of a Fox / 2300-K car
requires use a later model, the M179, which has 36mm of backspacing, and therefore
places the wheel 12mm further inboard to clear the fenderwell. I bought two of each,
which seemed like the ticket, and thought I was all set. I was so wrong.
The M179 fit well in back right out the box. But the R58 was too far outboard. The
wheel was about 1/2" beyond the outer lip of the fender, and that was unacceptable. I
also REALLY wanted to be able to rotate my tires, and using two of each wheel would
not allow me to do that. I tried the M179s in front, since I did 8mm more width on each
side that most people. But the wheels shallower backspacing made it interfere both with
my coil-over spring set-up, as well as my calipers. I could run a spacer as small as 6mm, but no, that was out of the question.
(Spacers magnify the loads on the studs many times, and in my opinion, are unacceptable for use on any car, much less a race car with wide sticky tires. Even the
best studs can, and in my opinion will, break unless inspected and changed on a regular basis. Even hubcentric spacers magnify the loads significantly, and the
thought of losing a wheel at speed is a frightening one, at least to me. I know that many people run them with success, but I will not as long as I can help it. Even if I
could be guaranteed I would never fail a stud, the fear I would have while driving would not make it worth it. If this seems to be the ONLY solution to a wheel
fitment problem, then contact Coleman and have a set of custom hat-on-rotors made up that make up the difference, and can be machined to be properly
hubcentric, but even this is not ideal. The Ford hubs are meant to mate to the Ford wheels, I would like to keep it that way.)
So M179s and R58s in the front seemed to be out of the question, right? How was I going to do this? It was at this time that I heard from many people that the
front fenders can be modified with just a little strong convincing. (Convincing in this case requires a baseball bat, and a 5lb sledgehammer). I proceeded to bend out
the fenders as much as I could, and I am still convinced there is a little more left in them. Now the R58s fit in front! Yeah! Should I just keep the M179s in back?
Several friends pushed me towards not being satisfied with any set-up that did not allow me to rotate tires, and I took their advice. I set out to modify my caliper
brackets and replace the axles, with the goal being to relocate the entire assembly inboard 3/4", and therefore be able to use R58 wheels in back. I found a machinist
who would undertake the task.
Modifying the Caliper Brackets
Moving the calipers inboard is a non-trivial task. I sat down with the machinist and discussed our plan of attack. The section of the bracket that bolts to the axle had
to be left untouched, but the mating surface between the bracket and the caliper needed to be moved back ¾" of an inch. Unfortunately, the material was only
0.550" thick, so just milling it out was out of the question. We needed to add material in the back of the bracket first.
We started out by cutting and welding a piece of .750" thick steel bar stock to the back of the bracket. We were careful not to interfere with the mating surface of
the axle housing. We then drilled and reamed the holes through the new plate. We wanted to do this before any milling operations to be sure that the holes were
transferred to the plate exactly. We then hogged out .750" of steel from the top, which put us right through the old bracket, and 0.200" into the plate. Thanks to the
care and time spent by the machinist, the part came out beautifully. It is fully TIG welded, and painted black, as can be seen in the pictures.
Also necessary in this round of modifications was shortening the anti-moan brackets by 0.750". This was a simple job - we ground off the old weld, scribed a new
weld line, welded the ring brackets back on in the new location, and cut off 0.750" of material off the edge. They also worked beautifully.
Axles
While these bracket modifications were taking place, I ordered a set of axles from Moser. The axles needed to be 0.750" shorter than the SN-95 axles I was
using. This shorter length corresponds to the length of the Fox axle. (The SN-95 axles are longer due to the need for an exciter ring for the ABS system). So I
ordered a set of Fox axles with the 5 lug SN-95 bolt pattern. This axle is quite popular since a lot of people convert Fox cars to 5 lug. Overall, the axles fit nicely. I
pressed in ARP race studs, and I thought I was all set. I rebuilt the Traction-Lock at the same time, and put everything back together.
Spacer Rings
The snag came when I first tried to put the rotors on the axles. The inside "hub" of the axle is meant to keep the rotor concentric with the axle, and the bolt holes are
just to provide space for the bolts, not to center the rotor. Well, the center hub section on the axle was far too small, and the rotor was hanging solely on the axle
studs. The mistake was mine, not that of Moser Engineering. I had asked for Fox axles, and that is what I got. What I needed to ask for the SN-95 axles, that were
0.750" shorter. The SN-95 hub is in fact larger than the Fox hub, and I had the smaller Fox hub on my axles.
The rotor was badly off-center, and this was not acceptable. The solution was to make up a set of spacer rings which press fit on the axle hub, and provided a larger
hub surface for the rotor to ride on, providing a hub-centric rotor. Making a set of these small spacers is an expensive job for a machine shop. I was looking at
about $100 each. Yikes!! But Baer Racing seemed to have a part that would work great. Baer has a spacer that is actually designed for the 12" Corvette rotor in
one of their systems, which has an ID which is extremely close to the ID of the 11.65" Cobra rear rotor I was running. I bought a set for a bargain basement price,
after fighting my way through a customer service rep who had no idea what he was talking about, and continued to
endlessly and ignorantly say "they won’t fit, they won’t fit", claiming they would fit on my axles, but not inside my rotors. Idiot.
When I received them, they fit beautifully inside my rotor, just like I thought. They were meant to fit on a Fox axle. Well guess what, they don’t. They are
specifically designed for this, but they don’t fit. My Mosers were the same as the stock axles which Baer claims these parts are for, but the parts were over 0.070"
off! So not only is their customer service pitiful, but so are their machinists and/or engineers. I spent a long evening with a sanding wheel creating a small pile of
aluminum shavings on my garage floor, but I finally got them to work.
Interestingly enough, another racer, Scott Bleiweiss was doing the EXACT same thing off in Massachusetts at the same time. He had Corvette rotors in back, so his
application was exactly the same as Baer Racing claims. Guess what, he had all the same problems I did, including the spacers not fitting on the axles. We checked
each other’s measurements, and racked each other’s brains. No Luck. The parts were just bad. But we had both made them work. Yeah!!
Conclusion
When I finally went to mount the wheels, I had failed to account for the steering travel. The
extended wheelbase of the Griggs set-up, along with the larger, wider, 275/40/17 G-Force R1
tires, created an interference problem at ride height with the front of the tire and the front fender
extensions. Keep in mind that the extensions on the car had already been switched to 1993
vintage, for extended clearance in this area, but that was not enough. The front outside of the tire
hit the fender extension on both sides whenever it was turned in (for instance, the left tire in a right
hand turn). The night before my GingerMan SAAC-MCR event, I was forced to do major
"modifications" when I ran a stretching bar, a la Winston Cup, from the radiator support to the
rear most corner of the fender extension, forcing it out several inches. I also had to remove the
internal factory bars, and redrill the flanges on the inside so that it would stay out straight. The
final result is that from the front of the car, the fender extensions seem to come out like little
wings, much like a Trans-Am or Winston Cup car. It doesn't look the greatest, but it works, and
it is aerodynamically effective.
Compliments
of Scott Whitehead
<swhiteh3@peoplepc.com>
http://www.rhinobrothersracing.com
Article 2
I have an LX and I didn't want to cut any holes or fasten new
body panels. So the scoops pretty much had to go under the bumper,
requiring a low profile.
I also lucked out because my splash shields were already long gone from the
spindles. These will have to be removed or modified to make ducting work.
I ended up getting some funnels at a parts store for about $2 each and going
from there. I don't have pics of the whole funnel but it was an especially
long one with a "narrow" taper that suited itself very well. I cut them
off so that the resulting taper point would fit inside my 2.5-inch silicone
high-temp hose, then racer-taped them to the hose.
I ran a bolt through the middle of the funnel with nuts and washers to keep it
"collapsed" in an oval and it just so happens that I could "clamp" it to the
fascia material with a large washer on the top. The funnel also
conveniently came with a small tab that allowed me to screw the very front of
the funnel through the fascia with a small screw. The whole point being
they're mounted securely but won't cause major damage if torn away by a parking
brick or something.
On the discharge end, I simply collapsed the tubing into a vertical rectangle
that tucks right into the center of the disc (no dust shields). Then I
slit the hose and ran a hose clamp through the slits, securing the hose to the
spindle by its internal spring wire by way of the hose clamp.
The rest, I zip-tied in place. The ducts have been in place for 18 months,
and have survived several track days, autocrosses, and many thousands of miles
of street driving. After a few too many parking-block incidents, I now
unbolt the scoops and tuck them up behind the fascia for safekeeping. They
stay put and invisible till I want to take a minute to fasten them back in
place. I have re-taped the ducts to the scoops but when I took these pics
I had only done the one nearest the camera, the far one had migrated into what I
would consider an unacceptable bend between the scoop and the duct. Easy
to fix as I did on the near one.
Needless to say, the most expensive part of this is the high-temp hose. If
I were doing it over again, to save money I'd use cheaper hose for the main part
of the hose and only use the high-temp for the last couple of feet leading up to
the brakes.
Compliments of.........
Fraser Elliott
MFE92@hotmail.com
