Buyer's guide to mountain bike wheels
By Guy Kesteven, Mountain Biking UK | Monday, April 30, 2012 11.00pm
Buyer's guide to mountain bike wheels Russell Burton
Looking for a new set of mountain bike wheels? Read on to find out what you should be looking for, along with explanations of some of the key jargon.
What to look for
Price comes first, but some of the cheapest wheels we’ve tested perform superbly. If you do decide to spend more, make sure you’re getting noticeable benefits. Bear in mind that decent after-sales service can make a more expensive set of wheels better value in the long run.
It's important to buy the right wheels for your bike, both in terms of diameter – 26in, 27.5in (650b) or 29in – and axle compatibility. Gone are the days when all mountain bikes had 9mm quick-release skewers front and rear. At the front, 15mm and 20mm through-axles are now common, along with 135 x 12mm or 142 x 12mm setups out back.
Once fit is sorted then you need to put your priorities in order. If you’re a tyre bursting, rim denting/wobbling animal then you need a wheel that’s tough, strong and compatible with fatter tyres.
If you’ve literally ground your last wheelset into the filth and it’s limping and creaking along on notchy, loose or seized bearings then you need to concentrate on the reliability of your next set. That means top quality bearings – either replaceable cartridge or serviceable cup-and-cone style – hidden behind the best seals possible. High-mileage or powerful riders also need to prioritise freehub quality and durability, and easily replaceable spokes are probably a shrewd idea.
If your current set has been fine then it’s just a case of finding something similarly tough and durable that offers the advantages you’re looking for. The obvious performance boost comes from reducing weight. That’s because saving weight in your rims gives far more noticeable bonuses in acceleration and agility than anywhere else on your bike.
The speed with which the freehub engages and reacts also makes a big difference for racers or anyone who needs to get back on the power as soon as possible between corners, jumps and the like. You don’t want a wheel that’s a complete twangy noodle though, particularly if you like to push hard through berms and rock gardens so make sure it’s tight enough for your level of riding aggression.
Finally, have a think about tubeless compatibility, because more and more tyres now come ready to pop up with a slosh of sealant as standard. Running a tyre sealed with liquid sealant rather than an inner tube increases pinch and thorn puncture resistance. It can also let you run lower pressure safer and they ride smoother too.
They can be an absolute arse to fit though, and won’t suit constant rubber swappers. To run a tubeless or tubeless ready system you need a sealed rim – or sealed rim tape – and built-in valve plus a tighter rim fit to stop them burping off.
Rim: Modern mountain bike wheels come in three diameters: 26in, 27.5in (650b) and 29in. Most modern trail rims have an internal diameter of between 19 and 24mm. The wider the rim, the better support and fatter profile it will give a bigger tyre. But bigger rims can be heavier.
Hub: There are loads of hub designs but it’s the bearings (and the seals covering them) that define smoothness over time.
Axles: An increasingly big deal as 15 or 20mm front axles and 135 or 142mm width, 12mm diameter rear through-axles appear on more and more bikes. Being able to change between axles is a futureproofing advantage.
Spokes: There are loads of different quantities of spokes, plus types, attachment methods and lacing patterns. The crucial thing is that they all stay tight, however hard you hammer them.
1/2/3 cross: The number of times a spoke crosses another between the hub and the rim. Fewer crosses means a shorter, lighter but less well supported spoke.
Bladed spoke: Spokes with a flat rather than round section. Aerodynamic benefits are dubious at mountain biking speeds, but the actual spoke shaping work can make them stronger.
Cartridge bearings: Self-contained bearings that you can pop out of the hub shell and replace once they feel rough.
Center Lock: Shimano’s unique disc brake rotor attachment. It uses a splined interface rather than the normal six-bolt fixing method.
Cup-and-cone bearings: User serviceable bearings using a cupped track on the hub and an adjustable cone track on the axle with ball bearings sandwiched between. They potentially offer a massive lifespan if you know how to look after them.
End caps: Push-on/pull-off caps on the hubs that convert them from one axle standard to another.
Pawl: The spring-loaded catches in the freehub that lock into the teeth on the hub body.
Straight-pull spokes: Spokes that thread directly into the hub/nipple both ends rather than hooking sideways into the hub with a J-bend.
Through-axle: A separate axle that slides through one dropout and the hub before screwing into the dropout on the other side. 15 or 20mm diameter at the front, 12mm at the rear.
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