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  Street or Track LLC :: Street or Track Products :: Street or Track 12x1.25" 'Trans-Am' Front Disk Brake System

Street or Track 12x1.25" 'Trans-Am' Front Disk Brake System
Street or Track 12x1.25" 'Trans-Am' Front Disk Brake System 

Street or Track 12x1.25" 'Trans-AM' Front Disk Brake System for DRUM spindles
Disc brake conversion kit for 1964-73 Mustangs.

Pictures show system mounted to our optional Big Spindle (not included in this kit but highly recommended for serious track cars).

Using only premium components, this complete 'turn-key' vintage legal* kit is based on the Boss 302 Trans-Am racing brake system of the late 60's.  Using 12" x 1.25" rotors mounted to an aluminum hat this kit offers a great weight savings over the original version.  Giant Kelsey Hayes style 67-Tbird calipers provide excellent clamping power and utilize the popular D1 pad.  Our custom spindle bracket requires no modification to your DRUM spindles and enables the kit to fit the popular vintage legal* 15" American Racing Torq Thrust D wheels.

*You should check with your rule book to confirm exact components allowed in class before purchasing.

Watch as we go over a few details on our 12 x 1.25" Trans-Am brake system, then watch how simple the installation is.

Please download and use the wheel fitment template:

Fits 65-73 Mustangs, Falcons and other Fords that used the same spindles.  Direct bolt on to 65-73 Mustang V8 OE drum spindles (65-67 any spindle, 68-73 drum version only).  Retains OE track width and enables use of 15x7 (or larger) vintage style & backspace wheels without spacers or modifications. 

Checkout real customer's installation pictures on our Facebook page:

Download our product flier

Kit includes:

  • 2 x 67-T-bird/Lincoln style 4 piston calipers complete with cross over tubes, stainless steel pad retention clips and your choice of Porterfield R4-S street pads or R4 Racing pads.  Calipers have had all the necessary machine work performed for a direct bolt on installation.  Finished in a high temperature silver powder coat.

  • 2 x 12" x 1.25" 2-piece heavy duty rotors with 36 directional cooling vanes. Rotors are cast and finish machined in the USA.

  • 2 x Hubs fitted with bearing races and standard length wheel studs (so you can use closed end lug nuts).  3" long ARP studs and open ended lug nuts also available.

  • 2 x Hub centric adapter shims.

  • 2 x Billet steel spindle/caliper mounting brackets.  CAD designed, CNC machined and plated for corrosion protection.

  • 2 x Timken inner bearings.

  • 2 x Timken outer bearings.

  • 2 x Timken inner dust seals.

  • 2 x Stainless steel braided brake hoses complete with all adapters to connect to caliper and stock hard lines.

  • 2 x Castle nuts (70-73 spindles use nut and castle style nut retainer).

  • 2 x Cotter pins.

  • 2 x Dust caps.

  • Grade 8 bolts and all the hardware to install the kit.

Optional components:

  • ARP 3" long wheel studs

All kits are custom built to your exact specifications.  If you are in a rush, please contact us to confirm current build time

General Specifications:
Wheel Size Required: Fits many 15" & larger wheels
Axle: Front


Caliper Specifications:
Name: 67 T-bird/Lincoln
Type: Fixed
Number of Pistons: 4
Piston Size: 1.946"
Construction: Cast Iron
Pads: Porterfield R4-S

Ideal for high performance and heavy duty street conditions the Porterfield R4-S compound remains a top performer in the realm of street/performance brake pads. With the R4-S compound giving a friction level up to .41.  This is an amazingly fast stopping brake pad.  Simply put, they will give you an impressive increase in stopping ability with very minimum amount of pedal effort.  Perfect for prolonged everyday street driving while also being capable of enduring the most severe use without fade.  It is also very rotor friendly.  Not recommend for racetrack use!

Porterfield R-4

Designed specifically for heavy duty motorsports, the Porterfield R-4 brake pad is able to maintain an average friction level of .50 within a very wide temperature range.  Using the latest in ceramic technology, the carbon based semi-metallic R4 materials allow the pad to absorb tremendous amounts of heat and dissipate it at a very even rate, while at the same time insulating excessive heat from the calipers.  Another inherent characteristic is the carbon kevlar material warms up to race temperature very quickly.  Optimum R-4 operating temperatures are 450F and above.  Throughout the entire heat range, the carbon kevlar material will give extremely consistent modulation and predictably smooth release characteristics up to threshold.  Not recommend for street use!

Finish: Durable high temperature silver powder coat.
Notes: Includes cross over tubes & stainless steel pad retention clips with grade 8 install hardware.  Fully assembled caliper with pads weighs 14lbs.


Rotor Specifications:
Type: Heavy Duty 2 Piece with CNC machined billet aluminum hat.
Diameter: 12"
Thickness: 1.25"
Venting: 36 Directionally vented vanes
Finish: Plain
Options: Stress Relieved (Heat Treated) or add Gas vent slots (both are a custom order).
Why use such a large rotor?  Well, simply put, heat.  The friction created by braking creates heat and the more and harder you brake the more heat is generated.  All that heat has to go somewhere and if the 'heat-sink' (rotor) gets so hot it can no longer absorb heat then the heat will migrate to other components.  These other components will include brake fluid and wheel bearings, not places you want increased heat.  The problem with large rotors is weight.  All that weight is unsprung which will affect suspension performance and increase stopping distances.

The rotor we use in this kit provides the best of both worlds.  Increased thermal mass due to its diameter and thickness yet lighter weight when mounted to an aluminum hat.  In fact, the rotor, aluminum hat, hub and stud combination used in this kit is 3lbs lighter than a standard 1970 Mustang rotor!  Additionally the increased width of this rotor allows the cooling vanes to be wider resulting in more airflow for cooling.

Directional cooling vanes aid in brake cooling

Our 2-pc 12" rotor with aluminum hat, hub and studs weighs 3lbs less than this 1-pc 11.25" 1970 rotor


Caliper mounting brackets:

Meticulous attention to detail and advanced computer modeling techniques ensure perfect fit.  Our brackets are custom CAD designed, CNC machined from a single piece of billet steel, then plated for corrosion protection.








Additional Features:
Master Cylinder (optional): Aluminum construction with see-through reservoir - no need to remove cap to check fluid level.  Weighs under 2lbs!  Ports exit passenger side.  Includes bench bleeding kit, new hard lines and fittings.  1" bore is ideal for this brake system.

Part Number: ST-12TRANS-AM
Price: $2,099.00

Year car
Year Spindle
Wheel studs

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Set of Timken bearings (4pcs)
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Spindle nut kit (2 sets)
Dust Caps (pair)
Moog Outer Tie Rods (2pcs)
1/2-20" Open end steel lug nut  1/2-20" Open end steel lug nut $1.49
Full Floating 9" Rear End System - 11.75" rotors, Kelsey Hayes calipers  Full Floating 9" Rear End System - 11.75" rotors, Kelsey Hayes calipers $3,499.00
Year Mustang
Add Intermediate Hose
Add 9'' Third Member Install Kit
Add -6AN Push on Hose End
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Customer Reviews

Author: Brad
Hi Shaun, I received the T/A brake kit yesterday afternoon. Its "AWESOME"! I showed it off to all the guys at the shop, and we are all very impressed.

Author: Sean
You will not be disappointed. Street or Track has high standards for quality and performance, and knows how to put a brake kit together.

The Granadas were a big improvement over the stock drums on the street, and I was happy with them when I started open tracking. I was running Porterfield R4S pads and Super Blue fluid and not having problems, but now four years later I realize how slow I was then. The faster I got the more I worried about brakes. I was at the point where under heavy braking adding more pedal pressure did not slow me any faster. I thought about trying different pads and master cylinder but felt it would be a waste of time and money trying to improve that system.

Along with the new brakes I replaced my 15/16 with your 1" master cylinder and switched to R4 pads. All of this really was a major improvement. One thing that stood out was that braking actually got better throughout a 20 minute session. I found myself braking way too early because I was slowing so much faster. What I did not expect was the confidence boost. The peace of mind of having no concerns about the brakes. I still remember the feeling of being on track and realizing that I wasn't thinking about brakes anymore.

The instructions were great and having all of the parts included and everything fit right without clearance problems is exactly what I was hoping for and is exactly what I got. Absolutely worth every penny and minute spent getting them on the car.

As Charlie Jones put it in one of his Mustang Times articles, "On the track, if you're thinking about your brakes you have a problem that needs to be addressed." I was thinking about my old brakes a lot on the track but now that problem has been addressed.




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