Early Bronco Wheels & Tires

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Factory Wheel Size, Lug Pattern & Fitment for 1966–77 Ford Bronco

The 1966–77 Ford Bronco is one of the most iconic 4x4s ever built, and it remains a top choice for restoration and off-road builds. Whether you're aiming for a period-correct look or a trail-dominating rig, your wheels and tires can make or break the build.

This guide breaks down factory wheel specs, bolt patterns, and the best backspacing and offset recommendations for both uncut original fenders and cut Broncos with aftermarket flares.

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Factory Wheel & Tire Specs

All Models (1966–77 Bronco)

• Wheel Size: 15" diameter, 5.5" to 6" width (steel)

• Tire Size (Stock): 7.00-15 or 7.35-15 bias-ply

• Bolt Pattern: 5x5.5" (5 lugs on a 5.5" circle)

• Center Bore: ~4.25"

• Lug Type: Lug-centric

• Stud Size: 1/2"-20 thread pitch

• Factory Offset: ~0mm

Early Broncos shipped with narrow steel wheels and tall, skinny tires designed to work with drum brakes and compact suspension geometry. Fitment was tight, especially at the rear fender openings.

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Lug Pattern Overview

Model	Lug Pattern	Lug Count	Bolt Circle	Factory Wheel Size
1966–77 Bronco	5x5.5"	5	5.5 inches	15x5.5 to 15x6

The 5x5.5" pattern remained consistent across all early Broncos and shares compatibility with some F-Series trucks and Jeeps.

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Fitment for Uncut Broncos

Uncut fenders are prized by collectors and traditionalists, but they come with very limited tire clearance, especially in the rear.

Recommended Wheel & Tire Specs (Uncut)

• Wheel Size: 15x6 or 15x7 (Some 15x8's can work)

• Backspacing: 3.75"–4.25"

• Offset: 0 to -6mm

• Tire Size (Max Recommended):

  • 30x9.50R15 is the largest that will generally fit with 2.5" lift without rubbing

  • Some run 31x10.50R15 with minor rubbing at full compression

  • We have seen customers go larger with lifts even up to 5.5". Ultimately it's up to you to find the tire size and look that works for you.

Key Considerations for Uncut Trucks

• Keep it narrow: Wider tires will rub during suspension compression or full turn.

• Stock or 1"–2.5" lift recommended to minimize rubbing.

• Shorter shocks or travel-limiting bump stops help avoid contact during flex.

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Fitment for Cut Broncos (with Fender Flares)

Cut fenders open up the possibilities for more aggressive tire and wheel setups. Whether you're adding fiberglass flares or steel flares, you’ll gain much-needed clearance front and rear.

Recommended Wheel & Tire Specs (Cut)

• Wheel Size: 15x8, 15x10 or 17x9 - Plenty of other sizes can work as well.

• Backspacing: 3.25"–3.75"

• Offset: -12mm to -25mm

• Tire Size Range:

  • 33x12.50R15 fits great with 2.5"–3.5" lift

  • 35x12.50R15 possible with 3.5"–5.5" lift, correct bump stop spacing

  • 37's and Larger can fit, but need a 5.5" or greater lift plus will likely require some trimming and custom fitment and/or body lift.

Key Considerations for Cut Broncos

• Wider stance = better stability off-road and better appearance with flares.

• Less backspacing keeps tires away from radius arms and inner fenders.

• Larger tires will require extended bump stops or trimming of flare lips at full compression.

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Additional Fitment Notes

• Disc Brake Kits: Most aftermarket disc brake conversions (front or rear) require 3.5" backspacing or less to clear calipers.

• Tie Rod Clearance: On wide 15x10s, excessive backspacing can cause rubbing at full lock—test fit before final install.

• Steering & Suspension Mods: Lift kits, dropped pitman arms, and extended radius arms all affect how aggressively you can spec your wheels.

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Backspacing vs Offset Quick Reference

Wheel Size	Backspacing	Approx. Offset	Recommended For
15x6	4.25"	~+6mm	Stock or uncut builds
15x7	3.75"–4"	0 to -6mm	Uncut or mild builds
15x8	3.5"–3.75"	-12mm to -19mm	Cut with flares
15x10	3.25"–3.5"	-25mm to -32mm	Cut with big tires

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Final Fitment Thoughts

If your Bronco is uncut, keep things conservative—narrow wheels (15x6 or 15x7), 3.75"–4.25" backspacing, and tires under 31" to avoid body damage and rubbing. If your fenders are cut for flares, you can run 15x8 or 15x10s with 33–35" tires using 3.25"–3.75" backspacing for aggressive stance and proper clearance. Plenty of early Bronco owners run 37's or even 40's - just make sure you have enough lift and body clearance to properly fit.

In either case, backspacing and offset are more than just numbers—they control how your Bronco drives, flexes, and looks. Measure your setup, consider your lift and brake configuration, and build your early Bronco the right way—whether it’s for the street, the trail, or the show field.

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