Early Bronco Wilwood Rear Big Brake Kit

Wilwood Early Bronco Rear Big Brake Kit Buyer’s Guide

Upgrading to a Wilwood Early Bronco Rear Big Brake Kit delivers stronger clamping force, improved heat control, and more consistent stopping performance compared to factory rear drums. All Wilwood rear kits feature 4-piston calipers, available in red or black, and offer rotor options in either standard or slotted & drilled configurations.

Choosing the correct kit comes down to three things:

1. Wheel size

2. Axle bearing size

3. Original drum dimensions

Important:
76-77 Bronco models are always Large Bearing (3-1/8" OD).
66-75 Broncos may be Small Bearing (2-7/8" OD) or Large Bearing (3-1/8" OD).

Step 1: Start with Wheel Size

Wheel diameter determines which rotor sizes you can run.

15" Wheels Minimum – 12.19" Rotors

If you are running 15" wheels, this is your Wilwood rear brake option.

• #140-13733 – 66-75 Bronco, Large Bearing, 11x1.75 drums

• #140-13320 – 66-75 Bronco, Small Bearing, 10x2.5 drums

• #140-13664 – 74-75 Bronco, Large Bearing, 10x2.5 drums

• #140-13322 – 76-77 Bronco, Large Bearing, 11x2.25 drums

This setup is ideal for builds keeping traditional wheel sizes while stepping up to 4-piston Wilwood braking performance.

17" Wheels Minimum – 12.88" Rotors

Moving to 17" wheels allows for a larger rotor and increased braking leverage.

• #140-13321 – 66-75 Bronco, Small Bearing, 10x2.5 drums

• #140-13734 – 66-75 Bronco, Large Bearing, 11x1.75 drums

• #140-13323 – 76-77 Bronco, Large Bearing, 11x2.25 drums

The 12.88" kits are a strong performance upgrade for Broncos running 35" tires or heavier builds.

18" Wheels Minimum – 14" Rotors

For maximum braking performance, the 14" rear rotor kits require at least 18" wheels.

• #140-13332 – 66-75 Bronco, Small Bearing, 10x2.5 drums

• #140-13731 – 66-75 Bronco, Large Bearing, 11x1.75 drums

• #140-13333 – 76-77 Bronco, Large Bearing, 11x2.25 drums

These kits are designed for high-horsepower builds, oversized tires, and Broncos that demand the strongest possible rear braking performance.

Step 2: Confirm Your Bearing Size

Before ordering, verify your axle bearing size:

• Small Bearing: 2-7/8" OD

• Large Bearing: 3-1/8" OD

If you have a 76-77 Bronco, you have Large Bearing axles from the factory.

For 66-75 Broncos, bearing size must be confirmed before selecting a kit.

Every Wilwood Early Bronco rear big brake kit features 4-piston calipers and premium rotor options, giving you modern stopping performance with clean fitment tailored to your axle configuration.

Start with wheel size, confirm bearing size, match your original drum dimensions, and you’ll have the right kit the first time.

If you’re unsure which Wilwood rear disc kit fits your 1966-77 Ford Bronco, the Wild Horses team can help you identify the correct setup for your build.