Product Summary

Ford 9 Inch, Rear Position, 11.25 Inch Rotor Diameter

  • Disc brake stopping power for your Ford 9 inch or 8 inch rearend at nearly the same cost as rebuilding/replacing drum brakes
  • Kits includes two bolt-on caliper brackets, two 11-1/4" vented rotors, two GM metric style calipers (non-emergency brake), brake pads and hardware for increased stopping power
  • Fits over an axle with maximum flange diameter of 6-1/4" O.D.
  • Rotors have a 2.780" center hole with both 5 on 4-1/2" and 5 on 4-3/4" bolt circles
  • Fits "old" and "new" style big bearing (3.150" bearing O.D.) Ford housings and with axle offsets of a minimum 2-3/8" to 2-1/2"

Comes as a Kit

Key Specs

Bolt PatternDual: 5 on 4.5" | 4.75"
Rotor Diameter11.25 Inch
Rotor TypeVented
Caliper PistonsOne

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Speedway Motors 91031902 Details

Disc Brake Stopping Power at a Great Value

This economical disc brake kit for Ford 9 inch and 8 Inch axles is simple to install and provides big stopping power, at a price nearly the same as replacing original drum brakes. That Ford rear end handles the power to make it go, but these binders clamp down when you say whoa! Today’s average family sedan can stop from 60 MPH in 120 feet, at nearly 1G of deceleration. You need the same stopping power. Your passengers, you and your car deserve the confidence of disc brakes and our kit delivers that confidence with exceptional value.

Superior to Drum Brakes

Aftermarket disc brakes are superior to original drums in many ways: more braking force, less brake fade, and easier service. Stopping power starts with our newly manufactured GM Metric D154 style single piston calipers, commonly found on 1978-88 GM G-Body and A-Body cars. Large 11-1/4” diameter, 1” thick vented rotors provide more stopping leverage than common 9” or 10” drum brakes. Brake pads are easier to change than drum shoes, and our brake kit includes a street-friendly organic compound for long rotor/pad life. Replacement pads are common sized, available from your local auto parts store. Looking for more aggressive stopping power? We carry race-grade D154 disc brake pads that drop in just as easily.

Fits Ford 9 Inch and 8 Inch Housings

This disc brake kit fits Ford 8 inch axles, as well as passenger car Ford 9 inch axle housings with “big bearing” ends (3.150” O.D. bearing, found on passenger cars from 1974-79). Included bracketry will adapt this kit to both “new style” and “old style” Ford 9 inch housing flanges with the 3/8” bearing retainer bolt holes. Bracket spacers are also included, allowing this kit to work with axle flange offsets of 2-3/8” or 2-1/2” common on Ford 9 inch passenger car rear ends. Axle flange offset is measured from the axle housing flange face (with bearing retainer removed) to the axle shaft flange face (side where the brake rotor/drum rides, including the thickness of the axle flange). 

Hardware and Instructions Included

Kit includes a detailed, step-by-step instruction sheet with images. The floating calipers include new Grade 5 slider bolts, with all remaining hardware of Grade 8 quality. Cast iron rotors feature a dual bolt pattern in 5x4.5” (Ford/Mopar/AMC) or 5x4.75” (Chevy/GM) to match your desired wheel hub pattern. Plus, this assembly will clear most 15” diameter wheels designed with disc brakes in mind. Note that there are no provisions for a parking brake, making this the perfect disc brake conversion kit for the budget-focused builder who prefers a basic upgrade kit.

  • Disc brake stopping power at nearly the same cost as rebuilding/replacing drum brakes
  • 11-1/4” diameter, 1” thick vented cast iron rotors dissipate heat faster than drum brakes
  • Serviceable design ensures good drivability and piece-of-mind when on the road
  • Street-friendly GM D154 style pads, replacements available nearly everywhere
  • GM “Metric” style single piston calipers with 7/16”-20 banjo-style inlets
  • Fits Ford “big bearing” 9 inch housings from passenger cars and 8 inch rear ends
  • Use with Ford 9 inch rear ends with 2-3/8” or 2-1/2” axle flange-to-housing offsets
  • Dual wheel bolt patterns covering all GM/Ford/Mopar (5x4.5” for 1/2” studs, 5x4.75” for 7/16” studs)
  • Use with 15” or larger disc brake-style wheels
  • Easy bolt-on installation w/ included instruction sheet
  • Includes heavy steel mounting brackets, Grade 8 hardware and nylock nuts (everything you need)


  • "Old-style" big bearing 9" Ford axle
  • "New-style" big bearing 9" Ford axle
  • 8" Ford axle
  • Axle housings with minimum axle offsets of 2-3/8" to 2-1/2"

This kit will NOT work on pickup housings or the 50's 9" housings as they only have about 2" backspace. The exception would be the late 50's station wagon rear ends.

When using with a Currie Axle with an o/d register of  2.795", the rotor is included in this kit with an i/d register of 2.78" and therefore will need to be machined by increasing the hole diameter in the rotor to match the Currie axle spec of 2.795"

Speedway Motors 91031902 Specifications

MFG. Part #91031902
BrandSpeedway Motors
Bolt PatternDual: 5 on 4.5" | 4.75"
Rotor Diameter11.25 Inch
Rotor TypeVented
Caliper PistonsOne
Caliper FinishNatural
Parking Brake ProvisionNo
Rotor ShapeRound
Hardware IncludedYes
Front Rotor IncludedNo
Front Caliper IncludedNo
Rear Caliper IncludedYes
Front Spindles IncludedNo
Master Cylinder IncludedNo
Brake Booster IncludedNo
Rear Rotor IncludedYes
Speedway Motors Catalog Part #910-31902
Rotor Thickness1.00"
Sold in QuantityKit
NotesWorks with 8" Ford and new and old style big bearing Ford 9" using 3/8" retaining bolts.
Axle Flange Offset2.36" - 2.50"
Ford Bearing End StyleBig Ford (Old/New) & Small Ford