Introduction to Bicycle Wheel Hubs

Short History of Hubs

The first wheels were probably round logs. Picture the pyramid-building Egyptians pulling giant cut stones over a bed of rolling logs. The next step in wheel evolution was two solid wheels, cut from round logs, solidly connected by an axle. The axle moved along with the wheels. Remember your toy cars? Then along came axles that did not rotate, that fit into the rotating wheels. The end of the axle was rounded as perfectly as possible and fit into a receptacle in the wheel. The friction was reduced with grease. This is the Conestoga wagon wheel. Finally came axles that did not rotate, fitting into a rotating wheel, with ball bearings to reduce friction--the bicycle wheel hub. 

Bicycle hub parts are:

a threaded axle that does not rotate with the wheel, and which connects the hub with the bike frame or fork

the hub body that is connected to the spokes, through which the axle runs, and which contains two concave surfaces facing outward along which the ball bearings roll

two cones, one for each side, each containing a concave surface facing inward along which the ball bearings roll, which are threaded onto the axle

ball bearings which are sandwiched between the 2 concave surfaces on the hub body and the concave surfaces of the 2 cones

spacers

two locknuts, each fitting against the outside of a cone (sometimes with intervening spacers) and locking down against the cone to hold it in place

either a quick release device or nuts and washers to hold the hub on the bike frame or fork

bicycle specific hub grease.

Hub spacing and axle size and features are discussed in the section on axle replacement.

Test Hub Adjustment--Frequently

Your wheels should rotate freely and smoothly on the bike, with absolutely no sideways slop. You can test hub adjustment with the wheel on the bike, but it is best to take the wheel off the bike.

On the bike. With the wheel on the bike, make sure the wheel is properly attached by the quick release or axle bolts. Hold the rim between 2 fingers and try to move it laterally. The rim should not move in any direction, except to rotate. Spin the wheel. It should rotate freely.

Off the bike. Take the wheel off the bike, hold the axles, and rotate it the wheel. You should not feel any catches or snags. Hold the axle in your fingers and try to move it in every direction at different places in its rotation. You should not be able to move the axle in any way except to rotate it.

Check your hub adjustment often. The harder you use your bike, the more often you should check the hubs. Using a poorly adjusted hub will ruin it.

Poor shifting, ghost shifts, and chain skipping are often caused by a loose rear hub.

Sloppy steering and front wheel vibrations are often caused by a loose front hub.

Broken and bent axles are caused by loose hubs.

When to Overhaul a Hub

How often should a hub be overhauled? Seldom, if you take good care of your bike. Most hubs are never overhauled. But when the hub needs an overhaul, not doing it will ruin your wheel. Here are some guidelines:

If you pressure wash your bike, you flush all its grease, and you may need to overhaul all your bearing systems and stop pressure washing.

Overhaul your hubs if you submerge your hubs riding across a creek. Better to get your feet muddy than your ball bearings.

After riding along a salt water beach, overhaul your hubs. Rent at the beach.

If you ride in wet weather, or on salted roads, you may need to overhaul your hubs annually.

If you commute and don't pay attention to hub adjustment, you may need to overhaul annually.

An overhaul is necessary if the grease in the hub dries out or hardens because you aren't using your bike. Frequently used hubs that are not exposed to real nasty conditions and which are tested often may never need an overhaul. I have never needed to overhaul a hub on my personal ride.

Recreational roadies may need an overhaul every 10,000 miles, more frequently if you ride in wet or salty conditions.

Some mountain bikers tear things up pronto and maybe should overhaul their hubs monthly.

Overhaul your hub if it feels dry or gritty, or if it can't be successfully adjusted.

Section Organization

The hub section is broken into subsections:

front bicycle hub adjustment and overhaul

rear bicycle hub adjustment and overhaul

bent or broken axle replacement

freehub body.

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