Converting Dayton 15-Inch Tube-Type Wheels to 17.5-Inch Tubeless Is a Practical Upgrade for Lowboy Trailers

[MikePhua]

Why the Conversion Matters
Many older lowboy trailers, especially 25–30 ton dual-axle models, were originally equipped with 15-inch Dayton-style tube-type wheels. These wheels often use snap ring or split rim designs, which are increasingly difficult to service due to safety concerns and declining technician familiarity. Converting to 17.5-inch tubeless wheels offers several advantages:

• Easier tire mounting and dismounting
  
• Improved safety with modern one-piece rims
  
• Better availability of tires and parts
  
• Enhanced load handling and heat dissipation
  

The conversion is especially timely when multiple tires need replacement, making it cost-effective to upgrade the entire wheel system.
Understanding Dayton Wheels and Tubeless Compatibility
Dayton wheels are demountable rims that use wedges and studs to secure the rim to the hub. Tube-type Dayton wheels require an inner tube and flap, while tubeless wheels seal directly against the rim. When converting to 17.5-inch tubeless, it’s crucial to ensure:

• The new rims match the hub’s bolt circle and pilot diameter
  
• The offset is compatible with the trailer’s axle spacing
  
• The wedges and center spacers are suitable for tubeless grip points
  

Some tubeless rims use a different contour at the mounting surface, which may require updated wedges or spacers. Tire suppliers can help identify compatible hardware using catalogs from brands like Accuride or Firestone.
Recommended Rim Specifications and Sourcing
Several rim models have been identified as suitable for this conversion:

• Accuride 31868-175-PKGRY21
  
• Accuride 17575-WD
  
• Firestone 318-68175
  

These rims typically measure 17.5 × 6.75 inches and are designed for heavy-duty applications. Prices vary, but Chinese-manufactured versions may be available for around $90 per rim, offering a budget-friendly option for fleet upgrades.
Offset Measurement and Fitment Tips
Offset refers to the distance between the wheel’s mounting surface and its centerline. On demountable rims, offset affects how far the wheel sits from the hub. To measure offset:

• Lay the rim flat and measure from the mounting surface to the back edge
  
• Compare this to the centerline of the rim width
  
• Ensure the new offset maintains proper clearance between tires and trailer frame
  

Incorrect offset can lead to rubbing, uneven tire wear, or axle stress.
Tire Cost and Performance Comparison
While 15-inch bias-ply tube-type tires are inexpensive, they often lack the durability and heat resistance of modern radial tubeless tires. 17.5-inch tubeless tires offer:

• Higher speed ratings
  
• Better fuel efficiency
  
• Longer tread life
  
• Reduced blowout risk under heavy loads
  

Although initial costs may be higher, the long-term savings in maintenance and downtime justify the investment.
Field Experience and Practical Advice
One contractor in Iowa converted his lowboy trailer after six of eight tires needed replacement. He sourced 17.5-inch tubeless rims and confirmed compatibility with his existing hubs. A local tire technician still serviced his snap ring wheels but refused to allow employees to handle split rims, highlighting the safety concerns driving this shift.
Another operator in the Southeast found that switching to tubeless eliminated recurring tube failures and improved trailer stability during long hauls. He noted that the thicker rim design also reduced flex under load.
Conclusion
Upgrading from 15-inch tube-type Dayton wheels to 17.5-inch tubeless is a smart move for trailer owners seeking improved safety, performance, and serviceability. With proper rim selection, attention to offset, and consultation with tire professionals, the conversion can be completed efficiently. As older wheel systems become harder to maintain, this transition ensures continued reliability and compliance with modern standards.