Don’t know the difference between Boost and QR? Our guide is here to help\u2026 <\/p>
Are you baffled by the different axle options available for mountain bikes? Our guide below explains the common types of mountain bike thru-axles, as well as traditional quick-release axles.<\/p>
Like many bike-related things, axle standards seem to be subject to continual change, with new ones emerging, gaining traction, then sometimes falling by the wayside as tech trends move on.<\/p>
The main reason for this with mountain bike axles is the drive to build more robust wheels. A wider axle means the flanges on each side of the hub can be set further apart, increasing their bracing angle and, hence, the wheel\u2019s strength.<\/p> For the rear wheel, working in the opposite direction is the need to keep a reasonably small Q-Factor<\/a>, so the pedals aren\u2019t too far apart, because this lowers pedalling efficiency and ground clearance.<\/p> The chainline needs to be engineered to run efficiently too, which means moving the chainset and cassette ever further outboard as axle width increases. Plus the chainstays need to be splayed out more to fit a wider axle, which increases the risk of heel strike as you turn the pedals.<\/p> For mid-range and higher-spec XC, trail and enduro bikes<\/a>, thru-axles with Boost spacing are now the norm.<\/p> But you can still find lower-priced MTBs running on quick-release hubs or non-Boost thru-axles.<\/p> Super Boost<\/a> is the latest thing and downhill bikes<\/a> use wider spacing too. Meanwhile, Cannondale has its Ai system, which addresses the same problem in a different way.<\/p>