I have a stock 93 Cobra. I am looking to upgrade to the 94-04 PBR's as well as the 94-04 11.65 rear brakes.
Do I have to swap the master cylinder and gut the proportioning valve?
you shouldnt have to touch the PV since the rear calipers are the same size BUT to get the same pedal feel you might have to swap the MC since the front calipers will require a bit more fluid movement than the stock 60mm's youve got.
the front 94-98 calipers would be close (dual 38mm pistons) but the 99+ calipers (dual 40mm pistons) might create a soft pedal.
id try it first and see how they feel to you before spending $$ and effort on a new MC
you shouldnt have to touch the PV since the rear calipers are the same size BUT to get the same pedal feel you might have to swap the MC since the front calipers will require a bit more fluid movement than the stock 60mm's youve got.
the front 94-98 calipers would be close (dual 38mm pistons) but the 99+ calipers (dual 44mm pistons) might create a soft pedal.
id try it first and see how they feel to you before spending $$ and effort on a new MC
For more fluid movement I would go larger to say a 94-95 GT/V6 master?
Forgive me for asking a dumb question,
but are all the 94-04 Cobra calipers the "38mm pistons" and the 99-04 GT's the "44mm pistons"?
The MC and booster can stay. But you should do the prop valve mod. Gut the stocker and install an adjustable on the firewall.
You are running non-stock brakes on a car that the brakes were not setup for in terms of bias. Sure the calipers in the rear are the same, but the weight and rotor diameter is not.
If you aren't running stock brakes, you should use an adjustable valve.
MC can/should stay. The stock prop valve can stay as is, but it may save you some brake fluid and time later to just gut it now. Install adj. prop valve.
I would leave your rear brake setup in place. Here is my reasoning. Extra money for next to no gain, it is that simple IMO. You will be able to get these brakes to work great with the SN95 Cobra front setup. Good luck!
Caliper should clear - same as the cobra. The issue will be pads. The M7 vented rotor is thicker than the cobra, but the D347 pad profile (45mm Varga) designed for that rotor probably will not fit the 38mm Varga. The Cobra pads will fit the caliper, but may not provide enough clearance for the thicker M7 rotor. Should be interesting. The thing is, if you just want a 5-lug conversion for mostly street and 15" wheel drag racing, why are you trying to keep the vented rotor? Just go to the solid sn95 GT and call it a day. Or throw on those discbrakesrus 5 lug rotors I mentioned above and sell the sn95 rear brakes. .25" diameter difference is not going to be very noticable in this application.
I just picked up a complete rear 10.5" Varga set up off of a 91 Mark 7 at the local U Pull it.
While I was there I found a 96 V6 Mustang and yanked the rear rotors to compare. Diameter is almost identical. Rotor hat from the outside friction surface to the wheel flange surface is also identical. I tried the Mark 7 rotor on the Mustang and its the back side clearance between the rotor and the axle housing bracket that is different. This has me thinking that the 91-92 Mark 7 axle shafts are in fact longer to get that extra clearance.
So if you put the two rotors on a flat surface, the M7 would be taller at the axle hat? If so, by how much?
EDIT: I just went out and measured two rear rotors I have: The 10-11/64" SSBC/Turbo Coupe rotor measured 2.25" from the flat surface to the outside axle hat; the 11.65" Cobra measured 2.13" same protocol.
I am going to try and go back and get the axle housing brackets on Sunday.
I didnt have time nor the desire today to remove them. But none the less, I would like to have them to take measurements.
Ill take some pics this weekend.
We need to find someone with a '93 Cobra R and have them try and read a part number off their prop valve.
Also, i wonder if the Saleens used this setup for 91-92, or if they continued to use the 11.35" setup.
I agree it's a very poorly known, but interesting setup. I would think a 99-04 GT PBR front setup and this rear setup would be nice for someone wanting good brakes on a car they drag race and use 15" wheels on.
The thing I like about it aside from the ability to mount smaller rims, is that it has a vented rotor as opposed to the solid sn95 Gt/v6. For curiosity, I went to one or two of the national parts suppliers (e.g., RockAuto) to price these rotors; they are about $30 each, which is a huge discount to those conversion rotors sold by discbrakesrus. If I hadn't already bought the discbrakesrus versions, I think I'd try to fit the M7s on my set-up. But I'm into these for well over $130 now so it wouldn't be cost effective until I run them down - which in my experience on a streeet car, won't be for a very long time. I will keep this set-up in mind for the future. One point Jack Hidley made on another thread is that because the 45mm Vargas are so big, one would have to dial back rear bias to get the correct F/R balance. I dunno; I'll be playing with that for some time on my own car. Last time I killed a set of tires but I've since learned a little, so hopefully I'll get it right and for less expense.
Here is an interesting email regarding the 93 Cobra R model suspension and brakes. I had emailed a gentleman who owned an R model back in 2001.
I did not get info on the master cylinder, proportioning valve or booster, but many other tid bits are included. I am prefacing this with my email to him and his response. I hope he doesnt mind if I post this.
I was curious if you would be able to detail what is different on the 93
Cobra R's front suspension. Are the lower control arms SN95 units or the
same as 87-93's? what about the crossmember? Are the spindles the same as
SN95's? What about the rear axle? Are the axle shafts infact the Lincoln
Mark 7's and do they use a special bracket to mount the calipers? Thanks
again!
To answer your question about how the 93 R front suspension is different
then say a 93GT or a street Cobra. The only difference is the struts,
spindles, and brakes. The LCA is stock Fox, the swaybar is stock GT (not
Cobra). The SN95 spindle is modified by welding a spacer where the castle
nut goes since the Fox ball joint is longer then the SN95 ball joint. Any
hardened washer will work. The rotors are stock SN95 Cobra but the calipers
are a plain or standard PBR casting, not the ones with the work "Cobra" cast
in them. Lastly the struts are Koni DA Super Sport models with special high
rate springs. That's it, The K-member is stock Fox, no modifications.
In the rear, besides the Koni DA shocks and high rate springs the only think
is the Lincoln MK VII rear axle. This axle is the same as a Fox Mustang
except for the longer axles and the 10.5 inch diameter rear disc brakes.
This is all stock on a MK VII. The axle is the same width as the SN95
Mustang so the Cobra 11.65 dia rear disc brakes will fit.
I wrote this reply back then. I have since sold the R. Jack Hidley does have most of the info on the 93R. He contacted me as well as a number of other 93R owners a while back and compiled that info on the brake set. He knows as much as anyone on the system used by Ford.
Wow, lots of great information. I would like briefly to share my thoughts on the subject and try not to clog up this thread with excess information. The '93 Cobra is unique in that it (and the '93 Cobra-R) has the larger SN95 size booster with the dash bolt pattern for the Fox cars. Both the '93 Cobra and the '93 -R had 1" master cylinders. The preferred front caliper for a track / street application of this combination is the smaller 38mm piston of the '94 - '98 Cobra. If the 40.5mm pistons of the '99 - '04 calipers are used you will have the same type of pedal feel as the '94/'95 Cobra (because it used a 15/16" master cylinder) which is great for the street however will have a little more travel which can add up to a bad thing at the track if they are pushed hard. For the rear, your car does have the larger 45mm piston calipers (as does the '93 -R). We prefer the smaller 38mm pistons from the SN95 Cobras and the associated larger rotor. This gives you less pedal travel and a larger diameter rotor. It's also a better size match to the smaller 38mm front calipers. Lots of pads are available as well. For the proportioning valve, I can't recall what was used in your '93 Cobra. I do know that the '93 Cobra-R had a 250, .36 prop valve (250 psi split point and a .36 slope beyond that) which is quite small. This small valve was needed due the small piston front calipers and large 45mm rear calipers (a 45mm piston is 40% larger than a 38mm). Most adjustable prop valves have a .43 slope which is nice. Since the proportioning needs vary so much with the particulars of your cars set up, I recommend an adjustable valve.
Disagree - my math says it about 18% larger. On the front, I'm using the later (larger) Cobra PBRs with the 45mm rear caliper (the point the OP was making is that he wants to run 14/15" rears for drag racing) with the SVO M/C - I do not have pedal travel or sensitivity issues; will admit that I do not have front/rear knee-point bais dialed in. No comment on the rest.
The back spacing between the two discs appears different because one is solid and one vented and wider. The center line of the disc is at the same spacing.
FWIW i am running a 97 cobra rear brake setup and a 95 cobra front brake setup in my 89 and i used a 93 cobra MC/BB and i got rid of the stock PV totally and just put the wildwood inline to the rear and mine seem to have a good feel. i am running a low vac cam(11-13hg) on a turbo car with no canister if that matters
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