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Shimano SLX M666 Disc Brake

Average User Rating: (Outstanding)
Vital MTB Retail Partners:
Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry

Compare to other Hydraulic Disc Brakes

    Need more info? View our MTB Hydraulic Disc Brakes buyer's guides.

    Featured Review

    “powerful, consistent brakes”

    The Good: Powerful, consistent, reliable, durable

    The Bad: routine maintenance is required for peak performance

    Overall Review:

    I ran these brakes hard this season- bike park, dh shuttle laps, aggressive trails. What impressed me most was the consistent braking power even on the longest downhills.   The oversized ceramic pistons and ice tech brake pads keep the system fade free.  The lever design is comfortable for 1 finger braking.   I found the tool free reach adjustment very convenient.   Coming from Avid brakes, I had to get used to the power of the Shimano brakes.  The power comes on more quickly, requiring the rider to not drag their brakes.  SLX brakes require less pressure to engage thereby reducing hand fatigue.  In addition, I feel that I can brake later into corners which increases my speed.

    At $125 per brake, these are the best performing brakes on the market.  Get them.  You won't regret it.

    “great brake without a pocket break”

    The Good: engagement, consistent, easy to bleed, cost

    The Bad: there is no bad

    Overall Review:

    What can I say they are shimano brakes and truly have held up. I ran these when I first got my bike and they work flawlessly, low maintenance but easy to service when needed, combine with icetec rotors and your a stopping machine. I have rode these in Moab, varous desert and mtn conditions and worked the same through out creating nothing but confidence. I now have upgraded to xtr for weight savings but the power on these is amazing.

    “Excellent brake that won't break the bank”

    The Good: Powerful, reliable, easy to bleed (mineral oil), cheap, quiet when wet

    The Bad: The pads are held in by a cotter pin (minor quibble though)

    Overall Review:

    For the money, you can't find a better brake, in my opinion. Picked these up for $80 each brand new. Been on these brakes for about a year now and they have worked perfectly. Haven't had to bleed them at all, but like all Shimano brakes they use mineral oil, a plus in my book.

    They are a little grabby if you grab a fistful of brake in a panic, but I like that I can do one finger braking and I prefer to feather my brakes anyway. The stock pads that came with it are pretty good, too. They're quiet even during wet rides.

    If you don't care about the bling or don't need the extra adjustments of xt and xtr, get the slx and be done with it.

    “Best brake...for this price...”

    The Good: Not drastically different from XT, great stopping power, weight, looks

    The Bad: Not XTR, little to no modulation.

    Overall Review:

    For the money I don't think you can find a better brake. Totally simple to bleed and they look sharp. Could be better... But hey, it's called xt and xtr. So... Again...for the money it is a pretty good brake. I have used juicy, Hayes and others and I personally believe shimano is the easiest to maintain. You could have these on your bike for years.

    “Perfect Brake”

    The Good: One finger endos, reliable, easy to bleed.

    The Bad: Cotter pin.

    Overall Review:

    Great brake, I've got 596, 666 and 785. If I was going to buy again I'd get 666 for sure. 596 are bit less powerful and I wouldn't want to lose the brake cable adjust feature. The 666 really seem as powerful as the 785. The only difference seems you lose the screw-in pad retention pin and have a split pin instead and a slightly less bling master cylinder cover.

    “Shimano SLX M666”

    The Good: compact lever/master cyclinder. easy to bleed. reach adjust. only had to pay 75 bucks for front and rear. very very smooth feel.

    The Bad: absolutely nothing

    Overall Review:

    i was running the previous gen slx's brakes and those were pretty good, then both the calipers cracked at the mounting holes and called up shimano and since i work at a shop, the warranty process was very smooth. i recieved in mail two brand new rear m666 brakes, and since they were free and i only need the one rear, i sold the other one which paid for the front so all in all, i only had to pay for rotors. im running them with the avid g3 rotors, 7 inch front, 6 inch rear and after getting the rotors/pads broken in, these brakes are phenominal. all the braking power i need and smooth modulation. compared to the elixirs ive ran, they are relativily low noise and by no means annoying. im using them for dj/light freeride and i hardly ever need more than 1 finger on the lever. ive had zero issues and when i get money i plan to buy the new xtr trail brakes and give those a try! 5 stars on the slx's for sure

    “Great brake for the price...hell, great brake all around.”

    The Good: Great stopping power. No noise or squeal. They just work, and really well at that.

    The Bad: None so far.

    Overall Review: I originally bought them for my XC/AM bike, but moved them to my FR bike when I found out the XC/AM frame was cracked. They were more than enough to stop the big bike (at least 40 lbs) on steeps and only 1 finger braking is needed. They also came on my new 29er and I couldn't be happier with them.  No fuss and they work great.  My FR bike originally had Avid Codes on it, which gave me non-stop problems.  It's nice to finally do lap after lap with no complaints about my brakes.

    “Just Awsome”

    The Good: very strong, good price easy to install

    The Bad: there is no bad

    Overall Review:

    best brake i ever bought , like to use them on my DH and my dirt jump bikes.

    “Solid Brakes”

    The Good: Well priced, great stopping power, low maintenance, easy to install, tool free reach adjustment, comes with those finned pads

    The Bad: I can't think of any

    Overall Review:

    These brakes are awesome. You really can't beat them for the price. I haven't had to do any maintenance on these since I got them. Shimano brakes in my opinion are also the easiest to bleed. They have tons of stopping power. I run these on my freeride bike and have used them at multiple bike parks and tons of downhill runs. I've never had to use more than one finger on these brakes. The reach adjustment also works great. My brother has ridden his avid codes the same amount as me or less and they are in need of a bleed and mine are not. The bottom line is if you want dependable, strong brakes and you're on a budget get these brakes!

    Vital MTB Retail Partners:
    Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry

    Specifications

    Riding Type
    Lever Material
    Mount Style
    Rotor Sizes
    Rotor Mounting
    Fluid Type
    Colors
    Weight
    Miscellaneous The new SLX disc brake borrows heavily from the XTR line such as the Ice Technology which reduces heat buildup.Other features: Oversized full ceramic piston for optimized light weight, rigidity, and insulation One-way bleeding--easy and clean bleeding system Heat resistant F03C metal pad included (Ice Technology) Short stroke Servo Wave mechanism for quicker engagement and higher level input 2-finger brake lever with ergo pivot Dial adjust lever reach Ispec compatible Includes pre-bled brake hose and mounting hardware Approx. 310 grams with brake hose Hose length front 1000mm, rear 1700mm
    Price $68.26
    Vital MTB Retail Partners:
    Chain Reaction Bicycles Jenson U.S.A. Competitive Cyclist Backcountry