Cobra calipers with 11" rotors

Inneh · Feb 27, 2021

So today I found out I may have access to a 2000ish cobra with brake system intact, however I still have my silly 15" stock wheels, and not the funds to upgrade those at the moment since this was a surprise find, so the 13" rotors wouldn't clear. If possible I'd like to do this in steps. So I figure I'll grab the calipers and brackets, and hold off on the rotors, since ha ha ha, this junkyard rests its cars directly on the rotors.

That said... Anyone know if the stock 11" rotors are temporarily usable with the upgrade?

KRUISR · Feb 27, 2021

So you have a 2000 with the dual piston PBR. Why would you want to change calipers? Performance will be about the same. If just wanting the 13" rotor, get the Cobra caliper mounting brackets, they should bolt up to your existing calipers and simply add the 13" rotor.

Inneh · Feb 27, 2021

Ah, good to know. I thought the v6 and gt had single pistons. Yes, the end game is the larger rotors. Upon reflection that obviously wouldn't work without the rotors because the bracket is designed to hold them out farther... Duh.

I kinda want to splurge for some lighter weight rotors to go with lighter 17s, but damn those lw rotor prices.

KRUISR · Feb 27, 2021

Actually the Cobra rotors are only a small height difference versus your stock rotors.

13" Cobra - 1.72" high
10.86" Stock V6/GT - 1.82"

The Cobra brackets you mentioned you had access to might take that into consideration. Otherwise a simple shim (washer) might do the trick.

All 99-04 V6 & GT used the dual piston PBR calipers. Cobras had a different caliper and a unique caliper bracket (for the larger rotors).

Mustang5L5 · Mar 1, 2021

There’s no reason to swap out your current calipers to the cobra ones if you plan on retaining the 10.9” rotors.

your 99-04 V6/GT calipers have dual 44.5mm pistons and much more pad area compared to the 99-04 cobra caliper with 40.5mm Pistons. If using the same rotor, it’s a downgrade. Your current calipers are “bigger”

the performance aspect of the cobra brake package over the 99-04 GT/v6 caliper is taking advantage of the extra mechanical advantage of the 13” rotor. Just wait until you can all do it at once.

Blueinfan · Sep 30, 2021

Mustang5L5 said:
There’s no reason to swap out your current calipers to the cobra ones if you plan on retaining the 10.9” rotors.

your 99-04 V6/GT calipers have dual 44.5mm pistons and much more pad area compared to the 99-04 cobra caliper with 40.5mm Pistons. If using the same rotor, it’s a downgrade. Your current calipers are “bigger”

the performance aspect of the cobra brake package over the 99-04 GT/v6 caliper is taking advantage of the extra mechanical advantage of the 13” rotor. Just wait until you can all do it at once.

question: I'm upgrading my 4 lugs to 5 lugs on my 1991 LX. I've installed 95 spindles and installing calipers from a 99 GT. Should I dump the 99 Calipers and get the following from LMR
1. 1994-04 Mustang SVE Cobra Style Front Brake Caliper
2. Mustang Cobra Brake Master Cylinder (94-95)
3. Mustang Power Brake Booster (1993) Cobra

If I upgrade to the Cobras, what parts do I need?

thanks =!

Mustang5L5 · Sep 30, 2021

Cobra vs GT is a personal decision. There are pros and cons to both setups.

If you decide to go cobra up front, you need the calipers, rotors and compatible brake lines.

1993 cobra or 94-95 booster will work.

For the Mc the latest cobra calipers tend to be the 40.5mm versions. The older 94-98 38mm versions were discontinued other than existing stock that is floating around. If you buy a reman, it’s likely the 99-04 cobra caliper. With that said, I would recommend the 1993 cobra master cylinder for them

Edit: since this is the SN95 forum, just to be clear the above is foxbody related

Blueinfan · Sep 30, 2021

So then it's more of a personal choice on the Cobra's or GT? I thought Cobra's were better because of the stopping power. I see and hear a lot of people upgrading to the Cobra's so I thought they were way better.

I have all the parts for the GT upgrade. But found out I need to buy these because I'm upgrading the rears to All discs.

1986-1993 Mustang Rear Disc Conversion Plumbing Kit
- 1987-1993 Mustang 5.0 Maximum Motorsports Brake Line Adapter for 1994-95 GT 93 Cobra Master Cylinder

Mustang Brake Proportioning Valve Plug

KRUISR · Sep 30, 2021

Blueinfan said:
I thought Cobra's were better because of the stopping power.

The stopping power comes from larger diameter rotor, not necessarily the caliper.

An alternative that is not discussed very often is to use a proportioning valve from a non-ABS 94-04 mustang. The reason it works is the non-ABS cars have a single brake line to the rear (just like our Foxes), so it has the correct number of lines and gives the right balance for 4 wheel discs. The only trick is you need the keep/reuse the fittings that thread into the prop valve and re-flair the lines.

11" rotors still allow for 15" wheels to be used, pretty much a rotor any bigger needs larger wheels (when I was 4 wheel 4lug discs I had 11.8" front and 11.33" rear rotors and needed 16" wheels).

Mustang5L5 · Sep 30, 2021

So then it's more of a personal choice on the Cobra's or GT? I thought Cobra's were better because of the stopping power. I see and hear a lot of people upgrading to the Cobra's so I thought they were way better.

What do you consider better?

On paper, the cobra brake system is better. Larger rotors, more mass, better heat dissipation.

In reality, when it comes to your average street driven Fox body, it’s a wash. Most often, these brake systems are really limited by tires, which is a hige consideration on a light fox wothout ABS and where it’s a struggle to get bigger than a 245 tire on a lot of cars up front.

The GT setup does have smaller rotors. Less rotating mass, lighter setup, fits inside 15” wheels. The 99-04 calipers have big pistons and massive pad area. It’s great for drag oriented cars who just need one good stop and then can allow plenty of cool down. Lighter rotational mass for better acceleration as well.

The cobra setup is bigger. Heavier rotors, more rotating mass, needs 17” wheels up from and 16” out back (some 15” wheels will fit). It’s more of a road race setup.

On that first brake attempt, a 99+ GT setup and cobra setup will likely be within a few feet of each other. Each successive stop, the cobra setup will begin to outperform due to the ability to absorb more heat. Is this something you’ll be doing? Or would you be mostly cruising around with one good stop here and there with plenty of cool down?

The cobra brakes do look better. But if you are running smaller drag rims or rims that don’t show the brakes well then that won’t matter.

That’s why I say it’s a personal choice. Either system will be plenty adequate on a fox. It all comes down to what you are doing with the car and which fits your needs better

Blueinfan · Oct 1, 2021

Mustang5L5 said:
What do you consider better?

On paper, the cobra brake system is better. Larger rotors, more mass, better heat dissipation.

In reality, when it comes to your average street driven Fox body, it’s a wash. Most often, these brake systems are really limited by tires, which is a hige consideration on a light fox wothout ABS and where it’s a struggle to get bigger than a 245 tire on a lot of cars up front.

The GT setup does have smaller rotors. Less rotating mass, lighter setup, fits inside 15” wheels. The 99-04 calipers have big pistons and massive pad area. It’s great for drag oriented cars who just need one good stop and then can allow plenty of cool down. Lighter rotational mass for better acceleration as well.

The cobra setup is bigger. Heavier rotors, more rotating mass, needs 17” wheels up from and 16” out back (some 15” wheels will fit). It’s more of a road race setup.

On that first brake attempt, a 99+ GT setup and cobra setup will likely be within a few feet of each other. Each successive stop, the cobra setup will begin to outperform due to the ability to absorb more heat. Is this something you’ll be doing? Or would you be mostly cruising around with one good stop here and there with plenty of cool down?

The cobra brakes do look better. But if you are running smaller drag rims or rims that don’t show the brakes well then that won’t matter.

That’s why I say it’s a personal choice. Either system will be plenty adequate on a fox. It all comes down to what you are doing with the car and which fits your needs better

Won't be racing or anything. I'm too old to be doing this racing stuff. More like cruising to car shows, Cars and Coffee, to the store, along the coast.

For now I'm going to be installing some 1997 Cobra rims w/245/45/17, and 275/40/17. Until I can find the rims I really want.

Rims (17,18) sizes are just like the calipers, on what one prefers. I'm still looking.

From the pictures below can you tell if this MC is Cobra or GT

Mustang5L5 · Oct 1, 2021

Unfortunately no way to tell from that pic. Would need to pull the piston out and measure

KRUISR · Oct 1, 2021

What year is the MC and Prop Valve supposed to be from?

Blueinfan · Oct 4, 2021

KRUISR said:
What year is the MC and Prop Valve supposed to be from?

The 5 lug upgrade I purchased from eBay (and got ripped off) is from 1995 GT.

It included - Front and back calipers, axels(28 Spline), Booster, MC, and Wilwood(with 3/8-24IF inlet- part number 260-10922) Prop Vale

However, after reading people's input here I decided to get a 1993 Mustang Cobra's MC from LMR. The reason is that later on I would like to upgrade to the Cobra calipers.

I'm not a mechanic but an IT Security guy so all this Fox stuff is new to me. I go to forums and Youtube and learn.

thanks!

KRUISR · Oct 4, 2021

Looking at the pics of your MC and comparing to replacements on rockauto, I think your MC is the 1.0625" diameter type.

Replacement specs...
93 Cobra, 95 GT/V6, 95 Cobra

Personally I think you want the 95 GT/V6 style for any SN95 dual piston caliper.

Blueinfan · Oct 4, 2021

KRUISR said:
Looking at the pics of your MC and comparing to replacements on rockauto, I think your MC is the 1.0625" diameter type.

Replacement specs...
93 Cobra, 95 GT/V6, 95 Cobra

Personally I think you want the 95 GT/V6 style for any SN95 dual piston caliper.

I ordered the 93 Cobra MC from LMR 9 see pic below) because someone recommended it. They mentioned that it was better than then the one I had.

Cobra calipers with 11" rotors

Inneh

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Blueinfan

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1986-1993 Mustang Rear Disc Conversion Plumbing Kit

1987-1993 Mustang 5.0 Maximum Motorsports Brake Line Adapter for 1994-95 GT 93 Cobra Master Cylinder

Mustang Brake Proportioning Valve Plug

KRUISR

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That is…until I whipped out my Bissell

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Cobra calipers with 11" rotors

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