Shimano BR-M666 SLX Disc Brake Review - BikeRadar

Hot on the heels of new XTR and XT is the revamped SLX brake that has many of the features of its top-end brethren but with less bells and whistles for a more affordable pricetag. After being blown away by XT’s performance, SLX faces a lot of pressure to continue the impressive run.

Both pricing and weight remain roughly flat compared to the previous SLX brake (about £120 per end, excluding mounting hardware, and 990g a pair – 490g rear, 500g front – with full-length hoses, all mounting hardware and 160/180mm rotors), but everything else is changed. The result is a shift from the radial master cylinder of yore to the new compact double-barrelled inline setup and an emphasis on improving power and heat management.

Oversized calliper pistons place more even pressure on the pads, and a swap to full ceramic construction (older ones were aluminium cups with smaller phenolic inserts in the centre) adds further heat resistance. Cooling-fin-equipped disc pads add more weight but are designed to dissipate heat faster than standard pads.

On XT and XTR versions – where heat management features are combined with new Ice Tech rotors (steel/ aluminium/steel disc sandwich) – the heat and brake fade resistance make a difference on the trail, but with SLX it’s harder to determine emphatically without a lab test. But, even on long descents we never had any issues. Standard pads are available.

The short lever blades produce ample modulated power on just one finger allowing you to brake late and hard – a vast improvement over its predecessor. There’s still plenty of feel and feedback through the lever, so it’s not a case of power without control. The levers get hinged bar clamps to make removal easier, although they still aren’t flip-floppable from left to right without removing the hoses.

Although the new SLX is 240g heavier, and lacks the top shelf ‘freestroke’ pad contact adjustment and Ice Tech rotors of a comparable XT setup, it’s £80 cheaper, and is equipped with all the genuinely useful day-to-day features, at a good weight, and all for a great price for its performance punch. Rotors are now available in either Center Lock or six-bolt configurations in 160, 180 and 203mm, and you can also add the Ice rotors from XT if you want the full Ice Tech suite as all parts are available separately.

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