Things to bear in mind when buying a MTB Double Crankset

You don’t always get what you pay for: While the top-end carbon-based cranksets are undoubtedly things of beauty, they’re not much lighter than top-end aluminum-based cranksets.


Ditching a chainring doesn’t mean losing one-third of your gears: The conventional triple chainring setup leads to overlapping of gears, so a 3×10 drivetrain may only yield 18 or so unique ratios. This overlap is reduced on a double, and trouble-free chain lines mean there are no sprocket combos you can’t use.


Switching to a double won’t save much weight: You might not be saving more than 50g by doing without a granny ring, so don’t choose a double on weight grounds.


Be careful with your gear ratios if you’re not super-fit: Some bigger ringed doubles can leave you running out of gears on steep climbs; go for 26 teeth or fewer if you have fitness doubts.


Cranks that look good on the shop floor don’t always stay that way on the trail: While we like the look of black MTB double cranksets, the silver or polished outer crank surface options stay looking good for more rides.


Anatomy of a Crankset




Almost all manufacturers use shaped teeth, ramps and pins on the inner edge of chainrings to help guide the chain between the rings. Some are more efficient than others, but front gear mech positioning and adjustment is equally important. Only having two rings cuts down on chain line problems and, if twinned with a shorter axle, results in a shorter distance between your feet (Q factor), said to be more efficient for pedaling.




Different cranks use different spline setups on the axle. Some slide onto the spline and are fastened tight by a bolt threaded into the end of the axle. Others involve the crank being pinch tightened around them. In both cases, spacers dictate ideal positioning for chain line, crank clearance and a snug fit with smooth-running bearings and no play.


Bottom Bracket


Square-taper bottom bracket axles with cups and bearings inside the frame shell are still available but most new cranksets now have an oversized hollow axle fixed to one crank, a splined axle onto which the other crank is bolted and bearings that fit into cups outside the frame’s BB shell.


We’re not testing BB30 or other oversized cups/axles in this test, but it’s worth being aware that they’re creeping in at the top end of the market as a way of trimming weight and boosting drive stiffness on top end frames. A BB30 bottom bracket has bearing cups that press-fit into the frame.


Bash Guards


If your rides involve log hops and/or rocky step riding, you’ll probably already know that slamming the big ring on logs/rocks will damage the teeth. Double cranksets have smaller outer rings, reducing this problem, or you could get a crankset with a bashguard instead of the big chainring.


Stiffness and Weight


Extra weight can add stiffness to cranks just as less weight can add flexibility. The skill of making great cranks at any price is to create stiffness where it’s useful while trimming weight where it’s not. Just don’t expect very light and very stiff. There’s usually a trade-off.


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