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  • Shimano - XT RD-M8100 Rear Derailleur - Black

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  • Shimano - XT RD-M8100 Rear Derailleur - Black

Shimano XT RD-M8100 Rear Derailleur


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    1 Review


    XT RD-M8100 Rear Derailleur

    It's been a little while since we've seen an update to Shimano's coveted XT group. In fact, the last time we saw big changes was when things shifted to 11-speed, which should make it no shock at all that Shimano's new XT RD-M8100 Rear Derailleur comes along with the launch of 12-speed XT. The new derailleur packs in a new, larger 13-tooth pulley, and carries on with the proven Shadow RD+ low-profile tech that keeps things tucked out of harm's way when the trail gets loose, wily, and filled with menacing boulders hungry to take a bite out of bike components.

    The new derailleur comes in two versions, the M8100 and M8120. This particular model is built for one-by drivetrains, to be paired up with Shimano's new 12-speed cassette. It's capable of running both the 10-45t and 10-51t cassette, but won't fair well if you're hoping to run a two-by crank setup. The derailleur brings a new level of silence to the drivetrain thanks to decreased tension in the lower gear positions, plus an added bumper on the pulley cage. The shifting is a bit faster than on the 8000-series derailleur thanks in part to the larger pulley.

    One thing that we're thankful has stayed the same through the generations is the stabilizer switch that we saw trickling down from XTR in the previous model. When engaged, this switch helps to eliminate chain slap and dropped chains by increasing spring tension. This is a valuable option for suspension systems that require chainstays and pivots located close to the rear derailleur. The RD M8100 keeps a good thing going with some of the previous model's improvements, including the direct cable path. Your shift housing can enter the stop on the derailleur without the traditional loop of excess housing that often was the victim of contamination in yester-years.

    Shimano sticks with the old-reliable aluminum components in the XT derailleur. All of the linkage plates, knuckles, and cage sides are made from it, so while it may lack the carbon-fiber-laden aesthetic of the XTR line, it's more affordable, and if you're been running XT derailleurs as long as most of us around the office have, you know you'll get plenty of mileage out of it.

    • Shimano's workhorse rear derailleur goes 12-speed
    • Shadow RD+ with stabilizer switch reduces chain slap, chain drops
    • Lofty cage length is compatible with both of Shimano's 12-speed cassettes
    • Decreased tension at low gear keeps things smooth and quiet
    • New bumper on pulley cage reduces noise
    • Fast and precise shifting performance optimized for trail riding
    • Durable aluminum construction holds up to trail abuse
    • Compatible with 1-by-12 groupset, for 2-by applications reach for the RD-M8120
    • Item #SHIU18I

    Tech Specs

    Cage Length
    Cassette Range
    10 - 51t
    1 x 12
    Shimano 12-speed
    Recommended Use
    Manufacturer Warranty
    2 years

    Tech Specs

    • Reviews
    • Q & A

    What do you think about this product?

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    Crank Away!

    • Familiarity: I've used it once or twice and have initial impressions

    Had my first ride on the new XT 12 speed derailleur and I am drinking the cool-aid!

    Here is what I liked:

    1. The install was a breeze.
    2. The shifting is crisp and quick. Better than X01 I think
    3. Reduced chain rattle is noticeable compared to X01
    4. Looks pretty cool

    Here is what I really liked!

    1. Shifting under load capabilities are no joke! I was cranking thru gears and this thing just took it!
    2. The decreased tension on the chain when in the 51t really makes pedaling smooth when grinding up some steep stuff.

    A couple of things to keep in mind compatibility wise:

    This derailleur is built for the 1x12 systems and can take the 51t or the 45t cassette. If you want to run 2x you will need RD-M8120 and that can only take the 45t.