Since around 4000 BC, the wheel has been a big deal. Now there seems to be more mountain bike wheel options than Subway sandwich fillings. A new set of round bits are one of the best bike upgrades you can make - so what do you need to know about them?
1. Rims - Obviously you'll want a 29in or a 26in sized rim depending on your bike. Rims can also feature double walls for added strength and sealed nipple holes for tubeless compatibility. Disc-specific rims are, as you may have guessed, not compatible with rim brakes.
2. Axles - For the front you'll either have a traditional quick-release axle, a QR15 (15mm through-axle) or a meaty 20mm job depending on your fork. At the back you'll need to choose from a regular quick-release again. RockShox Maxle or a downhill-spec 12mm bolt-through.
3. Hubs - Hubs are crucial. Bigger, smoother bearings will let you roll faster, and taller flanges equal a stiffer, stronger wheel. At the rear a tougher cassette body will increase lifespan. Around 150mm wide is downhill territory, some modern trail bikes use 142mm or 135mm.
4. Spokes - Good quality spokes will help your wheel stay truer for longer, and decent nipples won't round out while you're adjusting them or lose tension. Some hubs have straight-pull spokes that pull through an eyelet on the hub's flange rather than looping through.
5. Custom vs. Factory - Just as with your bike itself, whether you go for a custom build or a pre-built pair depends on both your needs and your wallet. Ask your local bike shop about their wheel-building charges or look online for sites offering wheel configurators.