Shimano SLX Dyna-Sys 10-speed transmission £359.94

Closer-ratio 10-speed shifting

BikeRadar score 4.5/5

Never has a significant performance change been so aesthetically undersold as on the latest 10-speed Dyna-Sys groupsets from Shimano. We've had the new SLX on test for several hard months, as well as using it on some of the 2011 bikes we’ve ridden, and it really does deliver on the trail.

If you’re into knowing the 'how?’, then Shimano squeeze 10 gears into the space of nine with a narrower chain and spacing between the cassette cogs. The chain is also directional, rather than double-sided, with different shaped sideplates to hook up and transfer (or not), depending on which way they’re heading up and down the block and chainrings.

There's a small but significant change on the chainset too – the big chainring is two teeth smaller and the grannyring is two teeth bigger. That means almost the same overall ratios when teamed with the massive 36-tooth rear sprocket, but more useable ratios in the big and middle rings.

The various front derailleurs get reshaped to follow the new rings closer and the Shadow rear mech and Rapidfire shifter pods are also decimalised with slight tweaks. The combined difference is immediately noticeable on the trail, with outstandingly light, smooth and accurate shifts in either direction.

They’re not quite as crisp as XT Dyna-Sys (which gets an alloy rather than plastic thumb lever), but even after a few months of intensive testing, the new chain designand narrower cog spacing mean it’s still slicker than nine-speed setups. If anything, it seems to get less rather than more heather/bracken/cut grass jammed in it when we’ve gone off-piste.

The gearing ratios really work too, letting you stay in the middle ring for longer on climbs. Whether the friction efficiency of the larger ring is offset by the increased chain angle drag we haven’t tested yet, but staying in the middle definitely makes quite a big difference psychologically.

It also makes a massive difference on more chain-influenced suspension bikes (particularly VPP and higher single pivot). Here, it avoids all the wallow and bounce associated with granny ring use for longer on steeper climbs. It’s also less bob-inducing than the 20-something-tooth smaller rings of SRAM/FSA double setups.

While the lack of any obvious cosmetic changes will be a definite disappointment for some out there, it does keep the price as low as possible, making SLX the current top value 10-speed trail transmission, despite recent price rises.

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