Changing Wheel Rim Size on a Ford 4500 Backhoe

[MikePhua]

The Ford 4500 Backhoe Legacy
The Ford 4500 backhoe loader was introduced in the late 1960s as part of Ford’s industrial tractor lineup. Built to compete with machines like the John Deere 310 and Case 580, the 4500 featured a rugged frame, torque converter transmission, and a hydraulically powered loader-backhoe combination. It was powered by a 3-cylinder diesel engine producing around 55 horsepower, with a reputation for simplicity and durability. By the mid-1970s, Ford had sold thousands of units across North America and Europe, particularly to municipalities and small contractors.
The 4500’s design included a fixed front axle and a heavy-duty rear axle with planetary reduction, making it suitable for rough terrain and heavy digging. Its wheels and tires were sized for stability and load-bearing, but as machines aged and applications changed, many owners began exploring rim size modifications to improve performance or adapt to new tasks.
Reasons for Changing Rim Size
Operators consider changing rim size for several reasons:

• Improve flotation on soft ground
  
• Increase ground clearance
  
• Match tire availability or reduce cost
  
• Enhance traction with wider tires
  
• Adjust gearing via rolling circumference
  

Terminology Note: “Flotation” refers to a tire’s ability to stay on top of soft surfaces like mud or sand. “Rolling circumference” affects travel speed and torque—larger tires cover more ground per revolution.
A contractor in Louisiana shared how he switched to wider rear rims to reduce rutting in clay-heavy fields. The change allowed him to work longer hours without getting stuck, especially during wet seasons.
Original Rim Specifications
The Ford 4500 typically came with:

• Front rims: 7.50x16 or 8.00x16
  
• Rear rims: 16.9x24 or 18.4x24 tires on 24-inch rims
  

Bolt patterns were standard 8-lug for the rear and 6-lug for the front, with hub-centric designs. The rear axle used a flange mount, while the front axle had a spindle hub.
Before changing rim size, it’s essential to measure:

• Bolt circle diameter (BCD)
  
• Center bore diameter
  
• Offset and backspacing
  
• Rim width and bead seat diameter
  

Compatibility and Sourcing Alternatives
When sourcing alternative rims:

• Match bolt pattern and hub bore
  
• Ensure offset does not interfere with fenders or loader arms
  
• Use heavy-duty rims rated for industrial use
  
• Avoid automotive rims unless reinforced
  

Some operators retrofit rims from agricultural tractors like the Ford 5000 or Massey Ferguson 165, which share similar bolt patterns. Others source aftermarket rims from suppliers specializing in industrial tire systems.
A fleet manager in Ontario found that rims from a Ford 7600 matched his 4500’s rear axle perfectly, allowing him to mount 18.4x26 tires for better flotation during snow removal.
Impact on Performance and Safety
Changing rim size affects:

• Speedometer accuracy (if equipped)
  
• Gear ratios and torque delivery
  
• Stability and tipping angle
  
• Brake performance due to rotational inertia
  

Recommendations:

• Keep overall tire diameter within 5% of original spec
  
• Recalibrate speed sensors if applicable
  
• Test braking on slopes before full deployment
  
• Avoid mixing radial and bias-ply tires
  

In 2020, a restoration crew in Texas upgraded a Ford 4500 with 20-inch front rims and 26-inch rear rims. While traction improved, they noted increased brake fade during downhill hauling, prompting a brake system upgrade.
Front Rim Considerations
Front rims are more sensitive to steering geometry. Wider or taller tires can:

• Increase turning radius
  
• Stress tie rods and steering knuckles
  
• Rub against loader arms or fenders
  

Solutions include:

• Installing wheel spacers
  
• Adjusting steering stops
  
• Reinforcing tie rod ends
  

A landscaper in Oregon added 2-inch spacers to his front hubs after switching to 10.00x16 tires. He reported smoother ride over gravel and reduced steering effort.
Tire Selection and Inflation Guidelines
When changing rim size, tire selection must match:

• Load rating (minimum 3,000 lbs per rear tire)
  
• Ply rating (8-ply or higher for industrial use)
  
• Inflation pressure (typically 35–45 PSI rear, 25–30 PSI front)
  

Use bead lubricant during mounting and check for proper seating. After installation:

• Re-torque lug nuts after 10 hours of use
  
• Monitor sidewall flex and tread wear
  
• Avoid overinflation, which reduces traction and increases wear
  

Legal and Insurance Implications
In some regions, modifying rim size may affect:

• Roadworthiness certification
  
• Insurance coverage
  
• Warranty terms (if applicable)
  

Operators should:

• Document all changes
  
• Notify insurers if machine is used on public roads
  
• Ensure compliance with local transport regulations
  

A municipal operator in New York had to revert to OEM rim size after a DOT inspection flagged his modified backhoe for excessive width.
Conclusion
Changing wheel rim size on a Ford 4500 backhoe can enhance performance, adapt to terrain, and extend the machine’s utility. However, it requires careful measurement, compatibility checks, and awareness of mechanical and legal implications. With proper planning and field-tested solutions, operators can safely upgrade their machines while preserving the legacy of one of Ford’s most enduring industrial workhorses.