Black Series Wheel Bearing Sizes: How to Identify Yours and Repack Them

Ask which bearings fit a Black Series camper and the usual answer is "pull the hub and read the numbers off the race." That works, but it means jacking up the trailer and dismantling a hub before you can even order the part. Most owners want to buy the kit first and do the job once.

You do not need to pull the hub. Black Series HQ campers run standard US trailer bearing sets, and which set you need is decided by one measurement you can take with a tape measure in about thirty seconds.

The short answer

Measure the diameter of your brake drum. Black Series axles come in two sizes, and each takes a completely different bearing set.

Both kits are genuine Timken, and both cover one wheel. A single-axle camper needs two kits. A tandem needs four.

How to tell which axle you have

Measure the brake drum, not the wheel. The 10-inch and 12-inch figures refer to the inside diameter of the brake drum, which is the standard way trailer axles are described. Your tire and rim diameter tell you nothing about the bearing size.

Three ways to check, easiest first.

1. Look behind the wheel. With the wheel on, you can usually see the outer edge of the drum through the rim. A 12-inch drum visibly fills more of the rim than a 10-inch one. If you have seen both, the difference is obvious. If you have not, measure.
2. Measure across the drum face. Pull the wheel and put a tape across the open face of the drum, edge to edge. It will read close to 10 inches or close to 12. There is no size in between, so a rough measurement is enough to decide.
3. Read the axle rating plate. If the axle carries a capacity label, 3,500 lb means the 10-inch set and 5,200 lb or 7,000 lb means the 12-inch set.

Do not assume from the model name. Axle specification has changed across model years and across the HQ range, and a camper that has had an axle replaced may not match anything. Measure the trailer in front of you. If your camper is a tandem, check both axles rather than assuming they match.

Why this matters more on a Black Series than on a typical travel trailer

Two things about these campers make bearings a maintenance item rather than a fit-and-forget part.

They get taken off pavement. Corrugated tracks put far more load cycling through a wheel bearing than highway miles do, and grease breaks down faster with heat and vibration. The service interval that suits a trailer that only sees interstates is not the right interval for a camper that gets used the way these are.

Delivery condition varies. Owners on the overland forums have reported campers arriving with bearings that were not torqued to spec and grease points that had not been greased. Others report finding play in a bearing within the first few thousand miles. Whether or not that matches your experience, it is the reason experienced owners in those communities treat a bearing inspection as part of taking delivery rather than something to worry about later.

If your camper is new to you and you do not know its history, pull one hub and look. It is an hour of work and it tells you what you actually own.

When to service

• Inspect yearly, or before any long trip.
• Repack every 12,000 miles on the 12-inch axles.
• Repack annually or every 10,000 to 12,000 miles on the 10-inch axles.
• Immediately, at any mileage, if you find any of the warning signs below.

Service both sides at once. Bearings on one axle live the same life, and if one has failed the other is the same age.

Warning signs you should not put off

• Play at the wheel. Jack the wheel clear, grip it at twelve and six o'clock, and rock it. Any perceptible knock means the preload is wrong or the bearing is worn.
• A hub that is hot to the touch after a drive when the others are merely warm. A dragging brake can also cause this, but a bearing is the first thing to rule out.
• Growling or rumbling that changes with road speed rather than engine speed.
• Grease thrown onto the inside of the wheel or the brake backing plate. That is a failed seal, and a failed seal means contaminated grease and, often, contaminated brake shoes.
• Dark, gritty or burnt-smelling grease when you open the hub.

Grease on the backing plate usually means the brake shoes are contaminated too. Shoes cannot be cleaned back to reliable friction, so plan on replacing the brakes on that axle at the same time.

What a repack actually involves

You will need the bearing kit for your axle size, a fresh cotter pin for every hub, high-temperature wheel bearing grease, a seal driver or a block of wood, and a torque wrench.

Never reuse a cotter pin. It is a single-use part, it costs a few dollars, and it is the only thing preventing the castle nut from backing off.

1. Chock, jack and support the trailer on stands. Never work under a trailer held up only by a jack.
2. Pull the wheel, then the dust cap. Straighten and remove the cotter pin, then take off the castle nut and washer.
3. Draw the hub off the spindle. The outer bearing will usually drop into your hand as the hub comes forward. Catch it.
4. Drive out the old seal and remove the inner bearing. The seal is destroyed on removal every time, which is why a new one comes in the kit.
5. Clean everything. Solvent-clean the hub bore, the spindle and the bearings if you are inspecting rather than replacing. The races must be spotless before you look at them.
6. Inspect the races. Pitting, scoring, blue heat discoloration or a polished track with visible steps means the race is finished. Races and bearings are matched sets. If you replace a bearing, drive out its race and fit the new one that came with it. Never run a new bearing on an old race.
7. Pack the bearings properly. Force grease through the wide side of the cage until it comes out the narrow side, working around the whole bearing. Palm-packing by hand is the traditional method and works; a bearing packer is faster and cleaner. A smear on the outside is not packing, and it is the most common reason a freshly serviced bearing fails.
8. Grease the hub bore lightly, fit the inner bearing, then drive in the new seal square to the bore. A seal driven in crooked will leak.
9. Refit the hub, the outer bearing, the washer and the castle nut.
10. Set the preload, below.
11. Fit a new cotter pin, bend the legs apart, and refit the dust cap.

Setting bearing preload

This is the step that decides whether the job lasts. Too loose and the bearing hammers itself apart; too tight and it overheats.

The standard tapered-roller procedure, which is what these axles use, runs like this:

1. Tighten the castle nut to roughly 50 ft-lb while rotating the hub. This seats the bearings and squeezes out excess grease. The hub should turn stiffly.
2. Back the nut right off until the hub is loose.
3. Retighten finger tight, just until you feel contact with no play.
4. Back off to the nearest cotter pin hole. Do not tighten forward to reach a hole. If the nut has to move, it moves in the loosening direction.
5. Check. The hub should spin freely with no perceptible rock at twelve and six o'clock.

Follow the specification in your axle manufacturer's manual where it differs from the above. The sequence is standard across the industry, but the seating torque figure varies by axle, and your axle's own documentation wins.

After the job

Drive a short loop, then park and put the back of your hand near each hub. They should be similar to each other and no more than warm. A hub that is noticeably hotter than its neighbour means the preload is too tight, and it is far easier to correct in your own driveway than on a shoulder three hundred miles later.

Re-check for play after the first few hundred miles.

When to replace the hub instead

If a race has spun in the hub bore, if the bore is scored, or if the drum friction surface is scored, cracked or worn past its limit, the hub itself is finished and no bearing kit will fix it. The Black Series brake drum hub ships fully assembled with both bearings installed and greased, which makes it the faster repair when a hub has failed rather than merely needing service.

What to order

For a single-axle camper, order two bearing kits, two cotter pins and a tub of high-temperature grease. For a tandem, double the bearings and pins. Add brakes for the affected axle if you found grease on the backing plate.

• 10-inch, 3,500 lb axles: Small Bearings, 10-inch Timken
• 12-inch, 5,200 to 7,000 lb axles: Big Bearings, 12-inch Timken
• Every hub, every time: Cotter pin

If you have measured your drum and are still unsure which set you need, send us the measurement along with your model and year and we will confirm it before you order. Everything ships from Upland, California.