Wheels appear to be a relatively simple. After all, the wheel was invented by a caveman wasn’t it? It’s just an outer rim attached to a central hub by a bunch of spokes. They are then attached to the bike via frame and fork axles. Simple.
In reality there’s more to them than just that. The variations in hub, spoke and rim designs make for an immensely wide choice.
Whichever type you require, wheels are never ever worth skimping on. You should always try to run the very best wheels that you can get. A pound spent on wheels is worth twice that spent elsewhere on the bike.
How wheels work
The hub is the middle of the wheel. The hub contains bearings, the freehub (where the cassette fixes on to), holds the wheel axle and is where the disc brake rotor bolts on to either via the usual 6-bolt system or the less common Centerlock splined system.
Hubs come in different axle type versions: Quick Release (QR) or 12mm/15mm/20mm bolt-thru designs. Which axle type you need is dictated by your fork and/or frame. Some hubs are convertible between axle types.
Rims are the outer hoop of a wheel. Usually made of aluminium but there are more and more carbon rims coming out. The rim is where the tyre fits on to. Rims come in different diameters (ie. ‘wheel size’). They also come into different widths.
Spokes are laced through holes in the hub’s flanges and attach to the rim via nipples. Spokes can be plain gauge (the same thickness throughout the length of the spoke) or double butted (thinner diameter in the middle portion of the spoke’s length).
How wheels differ
Hub bearings are either ‘cup and cone’ or ‘cartridge’ bearings. Shimano use cup and cone bearings because they last longer (NB: only if you regularly check and maintain them) and they theoretically make a slightly laterally stiffer wheel. Other brands’ hubs run on cartridge bearings which are a more practical option for those mountain bikers who prefer to simply replace the cartridge bearings as and when they wear out.
A hub’s freehub does two things. It holds the cassette. It also contains the internal mechanism that allows the wheel to freewheel when the rider isn’t pedalling and engage (or ‘pick-up’) when the rider is pedalling. Chris King hubs have famously instant pick-up, so are often well-liked by racers and riders who appreciate a quick response to their pedal input.
Hubs come in different axle type versions. Most are not adaptable to other versions. A QR hub will not work with a bolt-thru axle, for example. One exception to this is Hope hubs. Hope hubs are convertible to take pretty much any axle version you’re likely to come across. As such they are a popular choice for a lot of mountain bikers who want to ‘future proof’ their wheels for subsequent upgrades.
Rims come in different diameters and widths. The diameter is dictated by your bike which will either be 26in, 27.5in or 29in diameter. You cannot run incorrect diameter wheels on your bike. Different width rims are something that you can consider though. Narrower rims are lighter as there’s less material used, obviously. Wider rims are heavier but are often stronger, stiffer and – more importantly – they work better with larger volume tyres.
Plain gauge spokes are relatively heavy but good quality ones are incredibly stiff and strong. Most mountain bikers are better suited to double butted spokes which are significantly lighter yet still build into a sufficiently strong wheel.
You should consider whether the wheels can be run tubeless or not. Tubeless is a rim and tyre system that does away with a traditional inner tube, replacing it with a specifically designed rim, a specifically designed tubeless tyre and some liquid sealant. Tubeless systems are often lighter than using inner tubes. More importantly they prevent punctures.
Factory made or hand built
‘Factory’ wheelsets are off-the-peg, machine-made wheels. There is no customising. Sometimes they are not home-serviceable. They can be good value however. And they offer a certain kind of ‘factory team’ look that some riders like.
Factory wheelsets are an increasingly popular option but there’s still nothing like a good pair of hand built wheels. As well as the ability to select the exact sort of wheels that you want, the quality of their lacing and tensioning gives hand built wheels real performance and reliability advantages over factory wheels.
Which wheels should you buy?
Regular riders should be looking at mid-weight wheelsets with decent width rims, double butted spokes and the ability to convert the hubs to accept different axle types. Cartridge bearings are the practical option for most riders too. Factory wheels can be good value options but if you want the best, go custom hand built.
Racers will want the lightest system available. XC racers can run narrow rims without having any undue negative effect. Enduro and Downhill racers will need their wheels to be stiffer and very strong too. Lightweight and strong costs money. Custom hand built wheels will be the best bet here. Axle adaptability is not necessarily of high importance but serviceability is. Therefore cup and cone bearing hubs may have an advantage. Tubeless-specific rims are popular among racers too.
Leisure riders don’t need the most expensive wheels. Something that fits their bike, has modest width rims and fit-and-forget cartridge bearings is all that needs to be considered. Any aftermarket wheel will be a significant improvement on the wheels that come supplied with entry-level bikes.