Shimano XT Rear Derailleur
What the checker says75will not fit
Run variant by variant through the mountain bike builder’s own engine. Every sentence below is the checker’s, unedited. Nothing here says this part fits your bike; it says what it does and does not fit among the parts we hold.
Checked against 6099 verified mountain bike parts in this catalog. 5939 produced no finding of any kind; that is XT M8100 SGS (2019). XT M8100 GS (2019) clears 5929. Each variant produces 57 to 61 distinct errors and 0 distinct warnings.
Will not fit
- Will not fiterror · CassetteDrivetrain mismatch: Derailleur = Shimano 12-speed, Cassette = Shimano LinkGlide (CUES). Shifter, derailleur, cassette, chain and front derailleur must be one system. On 16 of the 60 verified cassettes in this catalog. Applies to all 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Shimano XT M8100 GS max of 45T. On 13 of the 60 verified cassettes in this catalog. Applies to 1 of 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Shimano XT M8100 SGS max of 51T. On 13 of the 60 verified cassettes in this catalog. Applies to 1 of 3 variants.
- Will not fiterror · CassetteCassette too big: 52T cassette exceeds the Shimano XT M8120 SGS max of 45T. On 13 of the 60 verified cassettes in this catalog. Applies to 1 of 3 variants.
- Will not fiterror · Front DerailleurDrivetrain mismatch: Derailleur = Shimano 12-speed, Front derailleur = Shimano LinkGlide (CUES). Shifter, derailleur, cassette, chain and front derailleur must be one system. On 12 of the 34 verified front derailleurs in this catalog. Applies to all 3 variants.
- Will not fiterror · Front DerailleurDrivetrain mismatch: Derailleur = Shimano 12-speed, Front derailleur = shimano-8. Shifter, derailleur, cassette, chain and front derailleur must be one system. On 12 of the 34 verified front derailleurs in this catalog. Applies to all 3 variants.
Drivetrain system, Chain. 15 more findings from the same check, on up to 6 of the 45 verified chains each.
Drivetrain system, Shifter. 12 more findings from the same check, on up to 11 of the 53 verified shifters each.
Drivetrain system, Cassette. 10 more findings from the same check, on up to 9 of the 60 verified cassettes each.
Actuation, Shifter. 9 more findings from the same check, on up to 1 of the 53 verified shifters each.
Cassette capacity, Cassette. 8 more findings from the same check, on up to 11 of the 60 verified cassettes each.
Drivetrain speeds, Cassette. 5 more findings from the same check, on up to 11 of the 60 verified cassettes each.
Drivetrain speeds, Shifter. 5 more findings from the same check, on up to 10 of the 53 verified shifters each.
Gearbox derailleur, Gearbox. 3 more findings from the same check, on up to 6 of the 6 verified gearboxs each.
Drivetrain system, Front Derailleur. 2 more findings from the same check, on up to 6 of the 34 verified front derailleurs each.
Open a variant in the builder to see the ones that apply to your own parts.
$110.00 to $130.00 MSRP·284 to 287 g
What the maker states
- System
- Drivetrain system Shimano 12-speed
- Speeds
- 12-speed (rear index count the maker rates it for)
- Actuation
- Mechanical (cable)
- Mount
- Standard hanger
- Maximum cog
- Largest cog 45 teeth (on 2 of 3 variants); Largest cog 51 teeth (on 1 of 3 variants)
A value shown as a set or a range differs between this model’s variants and is never one variant’s spec.
3 verified variants
| Variant | Maximum cog | Price (MSRP) | Weight | Source | Last checked | Build |
|---|---|---|---|---|---|---|
| XT M8100 SGS (2019) | Largest cog 51 teeth | $120.00 | 284 g | maker’s page | 2026-07-13 | Build with this |
| XT M8100 GS (2019) | Largest cog 45 teeth | $110.00 | 286 g | maker’s page | 2026-08-15 | Build with this |
| XT M8120 SGS (2019) | Largest cog 45 teeth | $130.00 | 287 g | maker’s page | 2026-08-15 | Build with this |
The rest of what the maker states2 not published
2 further fields the checker looks for are not published by Shimano, so we leave them blank rather than estimate them, and those 2 checks stay silent on this rear derailleur. They are maximum cog top and total capacity. Each is recorded as “not stated by the maker (not checked)”.
Source: each variant links the maker’s own page in the table above. Last checked 2026-07-13 to 2026-08-15.
Checked against
The checker ran this model against every verified part below that it has a slot for, the same way it checks a build in the builder. What follows is the verdict it actually produced for that specific pairing — not a recommendation, and not a guarantee any of these parts fits your own bike.
- 5DEV R-SPEC Trail/Enduro Cranks (Crankset) No conflicts found
- 9point8 Fall Line (Dropper Post) No conflicts found
- 9point8 Stout (31.8, 30mm) (Stem) No conflicts found
- ACID SLX 30 front (Front Wheel) No conflicts found
- ACID SLX 30 rear (Rear Wheel) No conflicts found
- Acros ZS44/ZS56 (Headset) No conflicts found
6 of 1858 counterparts with a page of their own that the checker actually probed this model against, in alphabetical order by brand and model — never by price, popularity or the verdict itself.