HubIt turns on two bearings on the spindle. The bearing cups are pressed into it, and its hollow middle is packed with grease.
Hub flangeThe face the wheel sits against. The wheel studs pass through it.
Wheel studIt is pressed into the flange. The wheel slides over the studs and a lug nut goes on each.
Lug nutIt threads onto a wheel stud. It clamps the wheel to the hub flange.
On the spindle 6
SpindleThe shaft on the axle end that the hub turns on. It does not turn. Its end is threaded for the spindle nut.
Grease sealIt is pressed into the inner end of the hub. It rubs on the spindle, keeping the grease in.
WasherA flat washer on the spindle. It sits between the outer bearing and the spindle nut. Also called a spindle washer or thrust washer.
Spindle nutIt threads onto the end of the spindle. It holds the hub and bearings on. Tightening it takes the play out of the bearings.
Cotter pinIt keeps the nut from turning loose. It passes through the slots in the nut and a hole in the spindle.
Grease capA cap pressed into the outer end of the hub. It covers the nut and keeps dirt and water out of the grease. Also called a dust cap.
Bearings 6
Inner bearingThe larger of the two tapered roller bearings. The grease seal holds it in the hub when the hub is pulled off.
Outer bearingThe smaller of the two tapered roller bearings. It comes out first once the nut and washer are off.
CupThe outer ring, also called the outer race. It is pressed into the hub and stays there.
RollersTapered rollers between the cone and the cup. They carry the load as the hub turns.
ConeThe inner ring, which slides onto the spindle. The rollers and cage stay on it as one piece.
CageIt keeps the rollers evenly spaced around the cone.
How this list was compiled: Every name checked on 2026-09-30 and kept only where two independent sources use it. (1) Dexter Axle's hub service procedure as printed in a trailer owner's manual, https://archive.org/details/manualzilla-id-5791589 , and Dexter's trailer running gear catalog, https://archive.org/details/manualzilla-id-6002166 (one source). (2) James G. Hughes, Brakes, 1987, https://archive.org/details/brakes0000hugh , a lending-library textbook read as the passages archive.org's full-text search returns. (3) Wikipedia, text only: Tapered roller bearing, https://en.wikipedia.org/wiki/Tapered_roller_bearing ; Castellated nut; Wheel stud; Lug nut; Spindle (automobile); Wheel hub assembly. (4) US Army TM 9-8000, Principles of Automotive Vehicles, for hubcap, bearing cup, bearing cone, spindle and hub oil seal. Cage rests on sources 2 and 3; hub flange on 1 and 2; every other name is in sources 1 and 2. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's product, nothing traced. Licence: own work
How it works
A wheel hub turns on two bearings around a fixed shaft, the spindle. The first view cuts the hub in half lengthwise. The second shows one bearing on its own.
Read the full guide
Read the cut from the outer end in
The grease cap comes off first. Under it a cotter pin locks the spindle nut. Behind the nut sit a washer and the outer bearing. The hub then slides off the spindle, with the inner bearing held inside it by the grease seal.
One bearing has four parts
The cup is the outer ring, pressed into the hub. The cone is the inner ring, on the spindle. Tapered rollers run between them, and a cage keeps the rollers evenly spaced.
The hub drawn has two tapered roller bearings that can be taken out and greased.
Some hubs use a sealed bearing unit instead, replaced as one piece.
Questions and answers
What are the parts of a wheel hub?
The hub and its flange, the wheel studs and lug nuts, the spindle it turns on, the inner and outer bearings, the grease seal, and on the end of the spindle a washer, the spindle nut, a cotter pin and the grease cap.
What holds a wheel hub on?
The spindle nut. It threads onto the end of the spindle against a washer and the outer bearing. A cotter pin through the nut and the spindle keeps the nut from turning loose.
What is a bearing race?
A race is one of the two rings the rollers run on. On a tapered roller bearing the outer race is called the cup and the inner ring is called the cone. The cup stays pressed into the hub.
What does the grease seal do in a wheel hub?
It closes the inner end of the hub around the spindle, which keeps the bearing grease in. It also holds the inner bearing in the hub when the hub is pulled off.