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Ford 9 Inch Bolt-On Rear Disc Brake Kit w/ E-Brake
Ford 9 Inch Bolt-On Rear Disc Brake Kit w/ E-Brake

Ford 9 Inch Bolt-On Rear Disc Brake Kit w/ E-Brake

Ford 9", Rear Position, Dual: 5 on 4.5" | 4.75" Bolt Pattern, 11.25 Inch Rotor Diameter

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Ford 9 Inch Bolt-On Rear Disc Brake Kit w/ E-Brake
Ford 9 Inch Bolt-On Rear Disc Brake Kit w/ E-Brake
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Part # 91031921
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Bolt Pattern:
Dual: 5 on 4.5" | 4.75"
Rotor Diameter:
11.25 Inch
Rotor Type:
Caliper Pistons:
Caliper Finish:
Parking Brake Provision:
MFG. Part #:
Minimum Recommended Wheel Diameter:
15 Inch
Rotor Thickness:
Rotor Shape:
Rotor I.D.:
Rotor Backspace:
Thread Pitch:
Hardware Included:
Sold in Quantity:
Works with 8" Ford, and new and old style big bearing ford 9" using 3/8" retaining bolts.
Rotor Material Type:
Cast Iron


As featured on Classic Truck’s Week to Wicked. Watch the transformation here!

If you dont want to spend an arm and a leg on a rear disc brake kit and still have to weld the bracket on, weve got you covered. This kit includes bolt-on caliper brackets, 11-1/4" vented rotors, 78-88 GM emergency brake calipers, brake pads and hardware.

  • Fits both 5 on 4-1/2" and 5 on 4-3/4" bolt circles
  • For Ford passenger car axles ONLY 
  • Fits axle with maximum flange diameter of 6-1/4" O.D.
  • For 15" and larger wheel applications ONLY

NOTE: This bolt on brake kit is designed to be used on 8" and 9" housings using 3/8" retaining bolts. If you want to use it on a 9" housing with 1/2" bolts, you will need to use the 3/8" hardware to do so. 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".

Axle Flange Identification Chart (GIF)

910-31921 Instructions (PDF)

Caliper Adjustment Instructions (PDF)

Item Details

With emergency brake calipers threaded to accept 7-16"-20 banjo bolt.


  • "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 diamter in the rotor to match the Currie axle spec of 2.795"

Some parts are not legal for use in California or other states with similar laws/regulations

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What's In The Kit

Each kit from Speedway Motors is carefully packaged and delivered right to your door. Below is a list of all the items you should expect to receive when you order this kit. Some of these items may also be available for sale individually if you're here looking for replacement parts.
  • Speedway Replacement 11-1/4 Inch Rear Brake Rotor
    Qty x 2
  • GM Metric Disc Brake to 9 Inch Ford Bracket Set
    Qty x 1
  • Ford 9 Inch Brake Bolt Kit
    Qty x 1
  • 1978-Up GM Metric Emergency Brake Caliper, LH, 5.45 Mount Bolts
    Qty x 1
  • 1978-Up GM Metric Emergency Brake Caliper, RH, 5.45 Mount Bolts
    Qty x 1
  • Instruction Sheet 91031902/91031921
    Qty x 1

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Q & A

  • Now that Project Chevelle is finally making real power, we want it all to get to the ground without breaking anything. Follow along as we install a 9-inch housing, third member, and some trick tubular control arms!
  • Day 1 afternoon update of the Speedway Motors and Classic Trucks Week to Wicked classic Chevy project.
  • The E-Stopp Electric E-Brake is an electronic push-button activated emergency brake option where the visible element is small and compact, and can replace the traditional hand or foot-operated emergency brakes.
  • After getting the control arms and drop spindles installed last time, we are dying to see what it looks like on the ground. Today we are working with the Speedway Deluxe Disc Brake Kit. Josh and Joe are on a roll!

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