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Derailleur capacity checker
Will your rear derailleur take these chainrings and this cassette? Checked against the maker's published limits.
Published limits
| Rear derailleur | Largest cog | Smallest cog | Front diff. | Capacity |
|---|---|---|---|---|
| Shimano road 12-speed | ||||
| Dura-Ace Di2 RD-R9250 | 30–34T | 11T | 16T | 37T |
| Ultegra Di2 RD-R8150 | 30–34T | 11T | 16T | 39T |
| 105 Di2 RD-R7150 | 34–36T | 11T | 16T | 41T |
| 105 RD-R7100 | 34–36T | 11T | 16T | 41T |
| Shimano GRX | ||||
| GRX Di2 RD-RX825 (12s, 2x) | 34–36T | 11T | 17T | 40T |
| GRX RD-RX820 (12s, 2x) | 34–36T | 11T | 17T | 42T |
| GRX Di2 RD-RX827-SGS (12s, 1x) | 51T | 10T | 1x only | 41T |
| GRX RD-RX822-GS (12s, 1x) | 45T | 10T | 1x only | 35T |
| GRX RD-RX822-SGS (12s, 1x) | 51T | 10T | 1x only | 41T |
| GRX Di2 RD-RX815 (11s, 2x) | 30–34T | 11T | 17T | 38T |
| GRX Di2 RD-RX817 (11s, 1x) | 40–42T | 11T | 1x only | 31T |
| GRX RD-RX810 (11s, 2x) | 30–34T | 11T | 17T | 40T |
| GRX RD-RX812 (11s, 1x) | 40–42T | 11T | 1x only | 31T |
| Shimano road 11-speed | ||||
| Ultegra RD-R8000-SS | 25–30T | 11–14T | 16T | 35T |
| Ultegra RD-R8000-GS | 28–34T | 11–12T | 16T | 39T |
| 105 RD-R7000-SS | 25–30T | 11–14T | 16T | 35T |
| 105 RD-R7000-GS | 28–34T | 11–12T | 16T | 39T |
| SRAM AXS | ||||
| RED / Force / Rival AXS (E1, 12s) | 28–36T | – | – | – |
| Rival eTap AXS (D1, 12s) | 28–36T | – | – | 39T |
| XPLR eTap AXS (12s, 1x) | 36–44T | – | 1x only | – |
| RED / Force / Rival XPLR AXS (13s, 1x) | 46T | 10T | 1x only | – |
| Campagnolo | ||||
| Super Record / Record / Chorus 12s, cage marked 29-34 | max 34T | min 11T | 16T | 39T |
| Super Record / Record / Chorus 12s, cage not marked | max 32T | min 11T | 16T | 37T |
| Ekar 13s (1x) | max 44T | min 9T | 1x only | – |
Changing gears? Chain length Gear calculator
Capacity = (big ring − small ring) + (largest cog − smallest cog). A dash means the maker doesn't publish that limit. Sources: Shimano Specifications (Ver. 2.7, 17 Sep 2026); SRAM RED AXS; Force AXS; Rival AXS; Rival eTap AXS; Rival eTap AXS capacity; Force XPLR eTap AXS; RED XPLR AXS; XPLR cassettes; SRAM 2024 Road Frame Fit Specifications; Campagnolo 12s rear derailleur manual; Ekar 13s manual; capacity formula from SRAM.
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