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Shimano XT RD-M8100-SGS RD-M8120-SGS Rear Derailleur - 12-Speed, Long Cage, Black

4.7 4.7 out of 5 stars 351 ratings

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Brand SHIMANO
Color Black, GS
Material Metal
Item Weight 1 Pounds
Mounting Type Braze-On Mount

About this item

  • Material: aluminum
  • Capacity: (GS) 35t [SGS] 41t
  • Cassette Range: [GS] 10-45t, [SGS] 10-51t
  • Gearing: 1 x 12
  • Compatibility: Shimano 12-speed

Product Description

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...

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Customer reviews

4.7 out of 5 stars
4.7 out of 5
351 global ratings

Customers say

Customers like the quality, strength, and value of the bicycle derailleur. They mention that it works really well, has smooth and precise shifting, and is reliable. Some appreciate the value for money.

AI-generated from the text of customer reviews

11 customers mention11 positive0 negative

Customers are satisfied with the quality of the bicycle derailleur. They mention that it has fast and crisp shifts, and it works well for 3 rides around 20 miles. Some say that the product is a good Shimano product and is flawless out of the box.

"...Mine has taken some hits, but still functions perfectly." Read more

"Works exactly as described! I love it! Great precise shifting." Read more

"...Flawless out of the box, highly recommend." Read more

"Got it at a discount, good shimano product, and get here fast." Read more

9 customers mention9 positive0 negative

Customers are satisfied with the shifting performance of the bicycle derailleur. They mention that it is smooth, precise, and does well when shifting while on an incline. Some say that the installation is quick and uncomplicated.

"Shifts smooth even under load on uphill climbs and durable. Mine has taken some hits, but still functions perfectly." Read more

"Works exactly as described! I love it! Great precise shifting." Read more

"...Shifting is smooth and precise, and and installation quick and uncomplicated. It also has a clutch that keeps the chain from slapping around...." Read more

"...When it's dialed in, it's fantastic: fast and crisp shifts, great gearing on the 10-45. But it's finicky...." Read more

5 customers mention5 positive0 negative

Customers are satisfied with the strength of the bicycle derailleur. They mention that it is reliable, and has a bullet-proof design. The clutch is much stronger, and it is a durable smooth derailleure.

"Bullet-proof design and flawless manufacturing combine to make this Shimano component a great 'bang for your buck' purchase...." Read more

"...Very precise, smooth and strong...I'd say that it takes much more abuse than the XTR ones...." Read more

"Much better than Sram IMO. The clutch is much stronger and I didn't have to change anything else.Works with the sram GX cassette and shifter." Read more

"Quality derailleur, new in box." Read more

3 customers mention3 positive0 negative

Customers find the bicycle derailleur to be a great bang for your buck purchase.

"...manufacturing combine to make this Shimano component a great 'bang for your buck' purchase...." Read more

"Good price..." Read more

"Worth the money..." Read more

Giselle at customer relations is the best!!!
4 Stars
Giselle at customer relations is the best!!!
After I received an empty package, I went through a little of a process in order to get my replacement. Giselle went above and beyond and followed up with me and got it handled. I was able to install the derailleur last night and only got to ride around the block as a test ride, I'm loving it so far. The one thing I noticed on the derailleur I'm not 100% about, is I wish the derailleur could have used the up shift lever to shift a single gear up when you use your thumb, or 2 up when you use the trigger finger. Either way, dumping 4 gears with the down shift is going to come in the most handy. I'll update my review as I get to run it on some trails.
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Top reviews from the United States

Reviewed in the United States on March 27, 2023
Reviewed in the United States on March 4, 2024
Reviewed in the United States on April 2, 2023
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5.0 out of 5 stars Super quiet, smooth and effortless shifting
Reviewed in the United States on April 2, 2023
This Shimano XT rear derailleur is the best I've ever installed. Shifting is smooth and precise, and and installation quick and uncomplicated. It also has a clutch that keeps the chain from slapping around. Use a high-quality slick cable for best performance.
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Reviewed in the United States on January 22, 2023
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Reviewed in the United States on March 6, 2024
Customer image
4.0 out of 5 stars Giselle at customer relations is the best!!!
Reviewed in the United States on March 6, 2024
After I received an empty package, I went through a little of a process in order to get my replacement. Giselle went above and beyond and followed up with me and got it handled. I was able to install the derailleur last night and only got to ride around the block as a test ride, I'm loving it so far. The one thing I noticed on the derailleur I'm not 100% about, is I wish the derailleur could have used the up shift lever to shift a single gear up when you use your thumb, or 2 up when you use the trigger finger. Either way, dumping 4 gears with the down shift is going to come in the most handy. I'll update my review as I get to run it on some trails.
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Reviewed in the United States on May 11, 2023
Reviewed in the United States on October 26, 2023
Reviewed in the United States on October 23, 2023

Top reviews from other countries

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Esteban Orozco
5.0 out of 5 stars EXCELENTE PRODUCTO
Reviewed in Mexico on January 15, 2024
Cliente Amazon
5.0 out of 5 stars Original
Reviewed in Spain on March 15, 2024
TechGeek
5.0 out of 5 stars Stabile Shimano XT, Schaltung
Reviewed in Germany on January 6, 2024
Amazon Customer
5.0 out of 5 stars Was what was ordered
Reviewed in the United Kingdom on October 30, 2023
Cliente Amazon
5.0 out of 5 stars Prodotto ottimo come visionato
Reviewed in Italy on April 29, 2023