RV & Trailer Parts – RV Trader Accessories Store

Most trailer problems don't announce themselves in a shop. They show up on the side of the highway - a hot hub, a locked wheel, trailer brakes that aren't responding - usually on the way to somewhere you wanted to be. Keeping your trailer's running gear in good shape is maintenance work, and it starts with having the right parts before something goes wrong.

This collection covers the core mechanical components that keep a trailer rolling and stopping safely: hub assemblies, wheel bearings and bearing repair kits, brake assemblies, brake actuators, breakaway systems, tires and wheels, stub axles, tow bars and baseplates, and the seals, caps, and hardware that hold it all together. Components come from Rigid Hitch, Dexter, Blue Ox, Kenda, and TRP International - brands that trailer manufacturers, dealers, and experienced owners actually spec and stock.

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Hub Assemblies and Trailer Bearings

The hub assembly is the central component of your trailer's wheel end. It houses the bearings that allow the wheels to spin, provides the mounting surface for the wheel itself, and - on braked trailers - contains the brake drum or rotor. When the hub or its bearings fail, the consequences range from costly roadside delays to a full wheel detachment at speed.

When to Replace

Trailer bearings should be repacked or inspected annually or every 12,000 miles - whichever comes first. A hub assembly replacement (rather than just repacking) is warranted when you notice:

• Grinding, rumbling, or squealing from the wheel area while towing
• Excessive heat in the hub after a haul - a hub that's hot to the touch after normal use needs immediate attention
• Grease leaking past the seal onto the wheel or axle
• Visible wheel wobble or lateral play when you grab the tire at 9 and 3 o'clock and push
• Any scoring, pitting, or discoloration on the bearings or races during inspection

Ignoring these signs doesn't delay the failure - it just moves it to a worse location and a worse time.

What's in This Collection

Hub assemblies in this collection are organized by bolt circle pattern (4-bolt on 4", 5-bolt on 4-1/2"), spindle type (straight vs. tapered, square shaft), and axle capacity (1,250 lb to 2,200 lb per hub). Many assemblies come pre-greased and include integrated Bearing Buddy protectors - spring-loaded grease fitting caps that maintain positive pressure in the hub to prevent water intrusion, a critical feature for boat trailers and trailers that see wet conditions.

Available configurations include:

• Single hub assemblies - for replacing one side at a time on a 4-bolt or 5-bolt pattern
• Paired hub assemblies - matched pairs for full axle rebuilds, available with tapered or straight spindles
• Emergency hub repair kits - everything needed to get a failed wheel end back on the road, organized by bolt circle and spindle size
• Trailer bearing repair kits - inner and outer bearing sets, seals, and hardware for repacking existing hubs
• Individual components - pressed hub studs, spindle nut lock shields, grease seals, dust caps, and E-Z Lube filler plugs for targeted repairs

Matching to your trailer starts with knowing your axle's rated capacity and spindle dimensions. The spindle size (typically 1-1/16" straight, 1-3/8" to 1-1/16" tapered, or 1" straight) determines which bearing set fits. The bolt circle determines which hub shell fits your wheels.

Trailer Brake Systems

Federal regulations require trailers with a gross weight over 3,000 lbs to have a functional braking system in most states. For travel trailers, toy haulers, boat trailers, and any other loaded trailer in that weight range, functional brakes aren't optional - and keeping them functional requires knowing which type you have and what the service items are.

Electric Brakes

Electric trailer brakes use electromagnets in each brake assembly to activate drum brakes when the tow vehicle's brake controller sends a signal. The brake controller reads deceleration and applies proportional voltage to the trailer's magnets - the harder the vehicle brakes, the more braking force applied to the trailer.

Electric brake assemblies in this collection are sold in pairs and cover common drum sizes. Replacement drum brake assemblies include the backing plate, magnets, shoes, and hardware needed to restore full braking function to one axle.

Surge (Hydraulic) Brakes

Surge brakes operate without a brake controller. The brake actuator integrates into the trailer tongue - when the tow vehicle slows, the trailer's forward momentum causes the tongue sections to telescope, driving a master cylinder that applies hydraulic pressure to the trailer's drum or disc brakes. The harder the deceleration, the greater the surge force, the more braking applied - automatically and proportionally.

Surge brakes are the standard on boat trailers because the system requires no electrical connection between tow vehicle and trailer, making it compatible with boat launch environments. They're also common on rental trailers.

Surge brake components in this collection include:

• Dexter Model 60 bolt-on drum brake actuator - 7,000 lb capacity, multi-fit ball coupler
• Dexter Model 6 disc brake actuator - disc brake version for higher-performance stopping on heavier trailers
• Replacement master cylinders - for Dexter/Titan Model 10 and 20 actuators, and the DX7.5 (750E) drum brake actuator
• Master cylinder filler caps and gaskets - for Dexter and Tie Down actuators
• Hydraulic drum brake assemblies - Dexter 7" x 1-3/4" paired drum brake sets

Breakaway Systems

A breakaway system activates the trailer's brakes automatically if the trailer separates from the tow vehicle while moving. On electric brake systems, a cable connects the trailer tongue to the tow vehicle - if the trailer detaches, the cable pulls a switch that sends full battery voltage to the trailer brake magnets, stopping the trailer independently. The system requires a charged battery on the trailer to function.

Breakaway system components in this collection include replacement batteries (9 Amp rechargeable, compatible with standard trailer breakaway systems) and block plate kits. Test your breakaway system annually - pull the breakaway pin with the trailer parked and confirm the brakes lock. A battery that won't hold charge is a non-functional breakaway system.

Tires, Wheels, and Tire-and-Wheel Assemblies

Trailer tires are not the same as passenger car tires. They're built for high load capacity at sustained highway speeds, not for steering and handling performance. Running passenger tires on a trailer, or running trailer tires at the wrong inflation pressure, is one of the most common causes of blowouts and trailer sway.

This collection includes:

• Kenda K371 Loadstar bias-ply trailer tires - 4.80x8, Load Range C, a standard size for small utility trailers, equipment trailers, and landscaping applications
• 13" trailer tires (no rim) - for trailers using a 13" wheel
• Tow-Master complete tire-and-wheel assemblies - 5.30x12 tire on a 5-bolt aluminum star spoke wheel, Load Range C, ready to mount as a spare or direct replacement

Always match replacement tires to the trailer manufacturer's specified load range and size. Overloading a trailer tire - even momentarily - generates heat that weakens the carcass, often causing a blowout miles or hours later rather than immediately.

Stub Axles

Torsional stub axles are self-contained axle units with integrated torsion suspension - the suspension and axle are one component rather than a separate leaf spring and solid axle arrangement. Torsion axles provide independent wheel movement, which reduces trailer bounce on rough roads and eliminates the leaf spring maintenance associated with traditional axles.

The 1,000 lb torsional stub axles in this collection include 5-bolt on 4-1/2" hubs with Bearing Buddy protectors and caps - appropriate for small utility and specialty trailers that require independent suspension.

Tow Bars and Baseplates

Tow bars and baseplates are for flat towing - pulling a dinghy vehicle behind a motorhome with all four wheels on the ground, rather than on a trailer. This is a common setup for Class A and Class C motorhome owners who want a car available at their destination without towing a car hauler.

The Blue Ox Avail tow bar and baseplate combos in this collection are vehicle-specific - the baseplate bolts to the towed vehicle's frame, and the Avail tow bar connects the baseplate to the motorhome's receiver. The Blue Ox Avail is rated to 10,000 lbs and includes the safety cables and accessories needed for a legal flat tow connection.

Flat towing requires a vehicle that is approved for flat towing by its manufacturer - not all vehicles can be flat towed without drivetrain damage. Confirm your dinghy vehicle's flat tow compatibility before purchasing a baseplate.

Selecting the Right Hub or Bearing Kit

The most common fitment mistake with trailer hub and bearing parts is matching by looks rather than by specs. Two hubs can appear identical but have different spindle bore sizes, different bolt circles, or different load ratings. Before ordering, confirm:

Bolt circle pattern - the number of lug bolts and the diameter of the circle they sit on. 4 on 4" and 5 on 4.5" are the two most common patterns in this collection. Measure between the center of two opposing studs (on a 4-bolt) or from the center of one stud to the center of the stud across the pattern (on a 5-bolt) to confirm.

Spindle type and size - straight spindles have a consistent diameter; tapered spindles are larger at the base and taper toward the end. Common sizes are 1-1/16" straight (for lighter axles), 1" straight, and 1-3/8" to 1-1/16" tapered (for 3,500 lb axles). The spindle size determines which inner and outer bearing cups fit.

Axle capacity - hubs are rated to a capacity that must match or exceed the axle's rating. A 1,750 lb per hub rating is appropriate for a 3,500 lb axle; a 1,250 lb per hub rating for lighter axles. Running a hub rated below the axle capacity is a failure waiting to happen.

FAQ

How often should I repack trailer wheel bearings? Most manufacturers recommend repacking or inspecting trailer wheel bearings annually or every 12,000 miles, whichever comes first. Boat trailers that are regularly submerged should be inspected more frequently - water intrusion dissolves grease and accelerates bearing wear significantly faster than dry-road towing.

What are the signs of failing trailer wheel bearings? Grinding or rumbling noise from the wheel area while towing, excessive hub heat after a normal haul, grease leaking past the seal, wheel wobble or lateral play when the trailer is stationary, and uneven tire wear are all indicators. Any of these warrant an immediate inspection - bearing failure at highway speed can result in wheel detachment.

What is the difference between electric trailer brakes and surge brakes? Electric brakes require a brake controller in the tow vehicle and a wiring connection between the vehicles. The controller sends voltage to electromagnets in the brake assemblies, activating drum brakes proportionally. Surge brakes are hydraulic and self-contained - the trailer's forward momentum during deceleration compresses an actuator on the tongue, which drives a master cylinder and applies the brakes without any electrical connection to the tow vehicle.

What is a trailer breakaway system and do I need one? A breakaway system activates the trailer's brakes automatically if the trailer separates from the tow vehicle while in motion. On electric brake trailers, this requires a battery mounted on the trailer - when the breakaway cable is pulled, the battery sends full voltage to the brake magnets. Federal regulations require a breakaway system on trailers over 3,000 lbs gross weight. Most states have similar requirements. Test yours annually by pulling the breakaway pin with the trailer stationary and confirming the brakes lock.

What is a Bearing Buddy and do I need one? A Bearing Buddy is a spring-loaded cap that replaces the standard dust cap on a trailer hub. It maintains positive grease pressure inside the hub, which prevents water from entering through the seal - particularly important for boat trailers that are regularly backed into water. The spring-loaded indicator on top shows whether the hub has adequate grease pressure. Bearing Buddies don't eliminate the need for regular bearing inspection, but they significantly reduce water contamination failures.

What is flat towing and how is it different from trailering? Flat towing (also called dinghy towing) means pulling a vehicle with all four wheels on the ground behind a motorhome, connected by a tow bar and baseplate rather than loaded on a trailer. It's a popular setup for motorhome owners who want a passenger car available at their destination. Not all vehicles can be flat towed - drivetrain design determines compatibility. Check your dinghy vehicle's owner's manual before purchasing a baseplate.

Can I replace trailer hub assemblies myself? Most hub replacements are within reach for a mechanically comfortable DIYer with basic hand tools - a socket set, torque wrench, and bearing packing tool. The process involves pulling the wheel and hub, inspecting the spindle, pressing or tapping in new bearings, repacking with fresh grease, installing new seals, and reassembling to the correct spindle nut torque. Emergency hub repair kits in this collection include all components needed for a roadside or shop repair. If the spindle itself is damaged or scored, professional service is required.

Keep your trailer running safely this season. Browse the full RV & Trailer Parts collection above to find hub assemblies, brake components, and maintenance hardware matched to your axle specs. For the full towing setup, the trailer hitches collection covers receiver hitches, ball mounts, and hitch pins, and the receiver hitches collection has vehicle-specific hitch options for your tow vehicle.

For RV owners thinking about maintenance before a trip, RVTrader's guide to buying a travel trailer and 14 tips to save your RV from an early death are worth reading before you head out.

Haven't found your rig yet? Search RVs on RVTrader.com to find a travel trailer, fifth wheel, or toy hauler that fits your towing setup.