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How to Select Axles and Running Gear

We stock a large selection of standard axle assemblies, replacement parts, and running gear to fit small to large trailers.  We also specialize in custom assemblies.  Convenience, quality, and economy are the reasons more people are turning to WHOLESALE TRAILER SUPPLIES on the web!


  • How to determine the Gross Vehicle Weight (GVW)?  When building a trailer, the total GVW must be determined in order to select the right axle or axles for the application.  GVW includes the weight of the empty trailer and the weight of the intended cargo.  (example: 2K empty trailer weight + 8K cargo = GVW of 10K)
  • How many axles?  After determining the GVW, the number and capacity of the axles must be selected.  (example: if you want 10K GVW and want tandem axles, the minimum required capacity is 6K per axle)
  • Brakes?  First, determine if you want brakes on each axle.  Most states require by law that at least one axle has brakes.  Some states require that all axles have brakes.  To determine how many brakes are necessary in a state, contact the local BMV. Second, determine which type of brake you prefer: electric, hydraulic single-serv, hydraulic free-backing, hydraulic duo-serve, hydraulic disc, or air "S" cam brakes.
  • Which type of spindles are going to be required?  Straight spindles are used mostly when the bed is over the tires or when low ground clearance is not required.  (example: flat bed or pull-type utility trailers, etc.)  Drop spindles are used when the lowest possible ground clearance is desired.  (example: livestock and horse trailers, car haulers, enclosed cargo van trailers, etc.)
  • What are the spring centers?  Spring centers are the CL (centerline) measurement of the spring mounting pads on the axle.  Spring centers are usually matched to the approximate frame width of the trailer.
  • Which bolt pattern?  The bolt pattern of the axles can vary depending on the capacity of the axle.  The bolt pattern also determines which type tire and wheel can be used. 
  • What is the length of the axle?  The term hub face is the measurement from the base of the wheel stud to the base of the wheel stud on the opposite end of the axle.  Another term is "track". Track is the center of the tire to the center of the opposite tire.  This measurement varies depending on what type of wheel is used, because each type of wheel (white spoke, OEM, custom) could have different offsest, changing the tire center.
  • Which type of springs?  There are two basic types of springs to choose from:  double eye or slipper springs.  Double eye springs are used with the shackle-type suspensions.  Slipper springs are the heavy duty springs used with slipper-type suspensions.  Complete sets of springs and u-bolt kits can be ordered with axles.
  • Which hanger kit?  There are several to choose from:  single, tandem, or triple for both double eye and slipper springs.  Hanger kits consist of spring hangers that attach to the frame, equalizers (tandem or triple hanger kits), shackle straps (if double eye springs) and all the necessary hardware.