3.5k Bearing kit (MAT)

What “3.5K bearing kit” means

• Refers to a set of components used to service or replace the wheel bearings on a 3,500 lb-rated trailer axle.
• Common on utility trailers, small campers, and boat trailers.

What’s included in the kit

A standard 3.5K bearing kit usually contains:

• Inner and outer bearings – allow the wheel to spin smoothly on the spindle
• Bearing races (cups) – surfaces the bearings roll against
• Grease seal – keeps grease in and dirt/water out
• Cotter pin or tang washer – secures the spindle nut
• Dust cap – protects the hub from contamination
• Sometimes includes grease or a grease fitting

Function (MAT context)

“MAT function” isn’t a universal industry term, but in maintenance/technical contexts it usually refers to the maintenance and assembly task/function of the kit. In that sense, the function is:

• M (Maintenance):
  Replacing worn bearings to prevent overheating, wheel failure, or axle damage
• A (Assembly):
  Providing all necessary parts to properly reassemble the hub after inspection or repair
• T (Traction/Turn):
  Ensuring smooth wheel rotation with minimal friction, which supports safe towing and load handling

Why it matters

• Prevents bearing failure, which can cause wheel lockup or detachment
• Reduces friction and heat buildup
• Extends the life of the axle and hub
• Improves safety and reliability during towing