Wheel building – The Hub
Wheel building is a rewarding skill to master. Possibly the simplest way to start is to buy a very cheep wheel from your local shop and use it for practice. By disassembling and then rebuilding it you can learn the basics of wheel lacing and spoke tensions. The reason a complete wheel is good place to start is that it has a hub, rim and the correct length spokes ready for you to work with. Arguably spoke length calculation is a whole skill in its own right.
The first question will probably be which hub? The choice of hub will be constrained by compatibility with your frame and other components. You’ll need to know the O.L.D, the number of spokes, and the gear and brake system you are using. Are you using a Campag or Shimano gear system for instance? The number of spokes will be dictated by your rim choice and possibly the lacing pattern you intend to use.
The O.L.D. or outer lock-nut dimension, as depicted above dictates weather or not the hub will fit in your frame or forks. Mountain bikes and hybrids Usually fit 135mm hubs whilst road frames will take hubs with an O.L.D of 130mm. 127mm on older frames or 120mm on track frames is common. You should use vernier calipers to check before going any further
The type of brakes and gears (or not) will likely influence your choice significantly. Some frames will only accommodate certain systems so it’s important to ascertain your bikes needs before falling in love with a particular component! Common categories are derailleur gears, internal hub gears, single speed hubs, disc or drum brake hubs.
Derailleur gears are probably the most common category but within that product group there are still many variations, each requiring particular specifications. The number of sprockets will be pertinent in all variations, ie: is your gear system 5,6,7,8,9,10,11 or 12 speed? The biggest question is weather your gear system is a Shimano HG cassette system, Campagnolo, SRAM XD or an old skool screw on type?
So what’s the difference between a two hundred quid Hope Pro 3 and a cheep Shimano Deore thing? Expensive hubs tend to contain replaceable sealed cartridge bearings whilst cheaper things tend to have loose ball races. High end components will often have ceramic bearings which are lighter and have more perfectly round bearings. The better the bearing the rounder the balls will be and the smoother the bearing race will be. Metaphorically speaking, cheep races will resemble fine sand paper and top end parts will have their races polished to a mirror like shine. Cartridge bearings can also be upgraded at a later time.
On top of smoother more durable bearings, high end hubs tend to be lighter and will have nicer freehub bodies or free wheels on rear hubs. A freehub will be an integral part of the hub so there wont be much scope for upgrades in future. Some companies offer the same component manufactured using exotic titanium alloys to reduce weight and improve durability. The primary characteristic you are looking for is the number of engagement points and engagement reliability. In any given 360 degree rotation, how many ‘clicks’ are there? Each click is an internal pawl springing into place.