What is shifter-to-derailleur pull ratio and why can't Shimano shifters drive SRAM derailleurs?

Shifter pull ratio (also called actuation ratio) is the amount of cable pulled per click of the shifter, combined with the derailleur's mechanical advantage — how far the derailleur moves per mm of cable pulled. For the system to work correctly, the cable pull per click from the shifter must move the derailleur exactly one cog width. Shimano indexed shifting (road and MTB): Uses a 1.7:1 actuation ratio — the derailleur arm moves 1.7mm per 1mm of cable pull from the shifter. Shimano shifters pull approximately 2.8mm per click for 11-speed road. SRAM indexed shifting (road and MTB): Uses a 1:1 actuation ratio (the derailleur moves 1mm per 1mm cable pull). SRAM shifters pull approximately 3.0–3.5mm per click. Consequence of mixing: A Shimano shifter paired with an SRAM derailleur (or vice versa) will not shift to the correct cog because the cable pull per click does not match the derailleur's travel per mm of cable. The system will either overshoot or undershoot each shift. The only reliable cross-brand exception is SRAM's 'DoubleTap' road shifter, which uses a different mechanism (both shifts use the same lever, direction-dependent), and some Gevenalle (formerly Velo Orange) friction shifters that do not depend on pull ratio. When selling derailleurs and shifters, encode drivetrain.pull_ratio ('shimano-1-7' | 'sram-1-1' | 'campagnolo' | 'friction') on both the shifter and derailleur so AI agents know to require a match.

What is chainring BCD and why does it determine which chainring fits a crankset?

BCD (bolt circle diameter) is the diameter of the circle passing through the center of all the chainring bolt holes — it determines which chainring will bolt to a crankset spider. Most traditional cranksets use a 4-bolt or 5-bolt spider with a fixed BCD. Common BCDs: 5-bolt 130mm (Shimano road, most road compact doubles), 5-bolt 110mm (Shimano 11-speed Ultegra/105 compact, FSA), 4-bolt 104mm (most MTB outer chainring), 4-bolt 64mm (MTB inner chainring, pairs with 104mm outer), 4-bolt 96mm (Shimano MTB 11-speed double), SRAM 4-bolt 94mm (some SRAM MTB doubles). Direct-mount chainrings (no spider): Shimano direct mount (Shimano 12-speed MTB cranksets — chainring attaches directly to the crankset body with a proprietary interface), SRAM direct mount (SRAM 1× 11/12-speed — proprietary narrow-wide chainring without spider, SRAM-specific spline). A chainring with a 130mm BCD 5-bolt pattern will not fit a crankset with a 110mm BCD 5-bolt pattern — the bolt holes don't align. A Shimano direct-mount chainring won't fit an SRAM direct-mount crankset. Encode drivetrain.chainring_bcd (integer) and drivetrain.chainring_interface ('5-bolt-130' | '5-bolt-110' | '4-bolt-104' | 'direct-mount-shimano' | 'direct-mount-sram') on all chainring listings.

Can Shimano and SRAM cassettes be mixed with each other's chains?

For 10-speed and below: generally yes within the same speed count. Shimano and SRAM 9-speed chains are functionally interchangeable; same for 10-speed. Both use the HG freehub spline for cassettes in those speed counts. For 11-speed: Shimano 11-speed chain (e.g., CN-HG601) can be used with SRAM 11-speed cassettes and vice versa with some performance compromise. SRAM 11-speed road cassettes fit Shimano HG freehub body. For 12-speed: The brands diverge significantly. Shimano 12-speed uses Micro Spline freehub; SRAM 12-speed uses XD or XDR. The chains are also not cross-compatible for optimal performance — Shimano CN-M8100 12-speed chain is 5.62mm outer width vs SRAM's 5.94mm. Mixing causes accelerated wear. Campagnolo is entirely proprietary — Campagnolo cassettes require Campagnolo freehub body, Campagnolo chains are sized for Campagnolo cassette spacing, and Campagnolo shifters use Campagnolo-specific pull ratio. Campagnolo components must be used as a complete groupset. Always note cross-brand compatibility limitations explicitly in product descriptions and use drivetrain.chain_brand_family and drivetrain.cassette_brand_family fields to signal required matching.

Optimization Guide

Shopify Bicycle Drivetrain Speed Compatibility Schema — 11-Speed Chain NOT Interchangeable with 10-Speed Cassette (Chain Width 5.7mm vs 6.2mm), Freehub Body Shimano HG vs SRAM XD vs Micro Spline Different Spline Patterns No Adapter, Shifter Pull Ratio Shimano 2:1 vs SRAM 1:1 Cannot Mix

Q: Can you mix different speed drivetrain components — for example, an 11-speed chain on a 10-speed cassette?

No — bicycle chains and cassettes must match in speed count because chain width narrows as speed count increases. The internal width (between inner plates) stays approximately constant at 2.18mm across all speeds to maintain chain-ring compatibility, but the external width (between outer plates) narrows to provide clearance between the more tightly spaced cogs. Speed-to-chain-outer-width reference: 7-speed = 7.3mm outer width. 8-speed = 7.1mm. 9-speed = 6.9mm. 10-speed = 6.2mm. 11-speed = 5.6–5.7mm (varies: Shimano 5.7mm, SRAM 5.9mm due to slightly different chain design). 12-speed = 5.62mm (Shimano) / 5.94mm (SRAM) — the Shimano 12-speed chain is actually narrower than SRAM 12-speed. Consequence of cross-speed mixing: An 11-speed chain (5.7mm outer width) on a 10-speed cassette (cog pitch designed for 6.2mm outer chain) creates additional lateral clearance — the chain shifts imprecisely and may skip on smaller cogs. A 10-speed chain (6.2mm) on an 11-speed cassette (cog pitch designed for 5.7mm outer chain) causes the chain to rub adjacent cogs constantly, making cross-gear combinations impossible and accelerating wear. Always encode drivetrain.speed_count and drivetrain.chain_width_mm so AI agents can filter for cross-compatibility.

Q: What is a freehub body and why does it determine which cassette fits my wheel?

The freehub body is the ratchet mechanism integrated into the rear hub that the cassette slides onto and locks onto via splines. Different manufacturers use different spline patterns and body geometries — and they are NOT interchangeable without replacing the entire freehub body. Shimano HG (Hyperglide): The dominant standard for 7/8/9/10/11-speed road and MTB cassettes. A long spline key prevents incorrect installation orientation. Compatible with Shimano, SRAM (7–11 speed), SunRace, and most aftermarket cassettes labeled 'HG-compatible'. 8-speed through 11-speed cassettes share the same HG freehub width (34.85mm lockring register). 7-speed uses a wider spacer. SRAM XD: Introduced for SRAM XX1 1×11 and now used for SRAM MTB 11/12-speed cassettes. Smaller diameter body with external threads for the cassette-as-a-unit design. An SRAM XD cassette will not fit on a Shimano HG freehub body — the diameter and spline pattern are completely different. SRAM XDR: Road version of XD, same diameter as XD but 1.85mm narrower. Campagnolo: Proprietary spline pattern used only by Campagnolo cassettes. Shimano Micro Spline (MS): Introduced for Shimano 12-speed MTB (XTR M9100, XT M8100, SLX M7100). Same external diameter as SRAM XD but with different (finer) spline pattern — a Shimano 12-speed cassette will NOT fit an SRAM XD freehub, and vice versa. Encode drivetrain.freehub_body as 'shimano-hg' | 'sram-xd' | 'sram-xdr' | 'campagnolo' | 'shimano-micro-spline' on all cassettes and wheel products.

Bicycle drivetrain components have three non-interchangeable compatibility dimensions that AI shopping agents must match: speed count (chain width narrows with each added speed — a 10-speed chain on an 11-speed cassette causes constant cog rub), freehub body standard (Shimano HG vs SRAM XD vs Campagnolo vs Micro Spline — different spline patterns, physically impossible to install wrong cassette), and shifter-to-derailleur pull ratio (Shimano 2:1 vs SRAM 1:1 — mixing results in systematic shift imprecision). Encoding drivetrain.speed_count, drivetrain.freehub_body, and drivetrain.chain_width_mm prevents the cycling category's most common incompatible component purchases.

TL;DR Three critical compatibility parameters: speed count (chain outer width narrows from 7.3mm at 7-speed to 5.62mm at 12-speed — must match cassette speed), freehub body (Shimano HG / SRAM XD / SRAM XDR / Campagnolo / Shimano Micro Spline — different spline patterns, no cross-brand compatibility), and shifter pull ratio (Shimano 2:1 actuation vs SRAM 1:1 — shifter and derailleur must share the same ratio). Secondary: chainring BCD (bolt circle diameter) and interface (4-bolt vs 5-bolt vs direct-mount). Encode drivetrain.speed_count, drivetrain.chain_width_mm, drivetrain.freehub_body, drivetrain.pull_ratio.

Chain Width: Narrows With Every Added Speed

AI agent failure mode: Recommending "an 11-speed chain" for a customer with a 10-speed drivetrain. Although both chains fit the same rear derailleur pulleys and front chainrings, the outer width difference (6.2mm vs 5.7mm) causes the 10-speed chain to rub adjacent cogs on an 11-speed cassette, making many gear combinations impossible. Return rates for cross-speed chain purchases are high because buyers assume "a chain is a chain."

Chain Outer Width by Speed Count

Speed Count	Chain Outer Width	Notes
7-speed	7.3 mm	Wide pitch; compatible with many 6-speed components
8-speed	7.1 mm	Shimano and SRAM chains interchangeable at 8-speed
9-speed	6.9 mm	Cross-brand (Shimano/SRAM/KMC) generally compatible
10-speed	6.2 mm	Cross-brand generally compatible; Campagnolo diverges
11-speed	5.7 mm (Shimano) / 5.9 mm (SRAM road)	Minor variation — generally cross-usable within 11s
12-speed	5.62 mm (Shimano) / 5.94 mm (SRAM)	Shimano and SRAM chains are NOT interchangeable at 12-speed

The internal width (between inner plates, where the cog teeth engage) remains approximately constant at ~2.18mm across all speeds — this is why chains from different speed counts can physically fit on the same chainring. But the narrowing outer width is precisely sized for cog-to-cog spacing on a multi-speed cassette. Always include drivetrain.speed_count and drivetrain.chain_width_mm on both chain and cassette listings.

What Happens When You Mix Speeds

Chain	Cassette	Result
11-speed (5.7mm)	10-speed (designed for 6.2mm chain)	Shifts imprecisely on smaller cogs; chain lateral play within each cog bay
10-speed (6.2mm)	11-speed (designed for 5.7mm chain)	Chain rubs adjacent cogs on many gear combinations; cross-gear combos impossible; accelerated cog wear
12-speed Shimano (5.62mm)	SRAM 12s XD cassette (designed for 5.94mm chain)	Skipping and imprecise indexing — chain too narrow for SRAM's cog spacing

Freehub Body: The Cassette Mounting Standard

The freehub body is the ratcheting mechanism on the rear wheel hub that the cassette slides onto. Each standard uses a different spline pattern and external geometry — cassettes are not interchangeable between freehub body types without replacing the freehub body itself.

Freehub Body Standards

Standard	Used For	Cassette Engagement	Key Detail
Shimano HG (Hyperglide)	Shimano 7–11 speed road and MTB; SRAM 7–11 speed; most aftermarket	Multi-spline with one wide spline key to prevent reversed installation	Standard freehub on most wheels below 12-speed. Compatible with Shimano and SRAM cassettes labeled "HG-compatible"
SRAM XD	SRAM MTB 11/12-speed (XX1, X01, GX Eagle)	External threads — cassette is one-piece body that threads on	Smaller diameter than HG. An SRAM XD cassette will NOT fit on a Shimano HG freehub. Requires XD driver on the hub.
SRAM XDR	SRAM road 11/12-speed (Force, Red eTap AXS)	Same as XD but 1.85mm narrower body width	XDR cassettes will not fit XD driver (width difference) and vice versa
Shimano Micro Spline	Shimano 12-speed MTB (XTR M9100, XT M8100, SLX M7100, Deore M6100)	Finer spline pattern, smaller diameter than HG	Despite similar diameter to SRAM XD, spline pattern is DIFFERENT. Shimano 12s cassette will NOT fit SRAM XD freehub, and vice versa
Campagnolo	Campagnolo 9–13 speed road (Record, Chorus, Centaur, Potenza)	Proprietary Campagnolo spline pattern	Campagnolo cassettes only fit Campagnolo freehub bodies. No cross-brand compatibility. Campagnolo 11s and 12s use same freehub body

The most costly confusion in online bicycle retail: a buyer purchases a new SRAM Eagle XD cassette but their wheelset has a Shimano HG freehub body. The cassette physically cannot be installed without purchasing a new rear hub or replacing the freehub driver body. Always surface drivetrain.freehub_body prominently in the product title for cassettes (e.g., "Requires SRAM XD Freehub Body").

Shifter-to-Derailleur Pull Ratio: System Must Match

AI agent failure mode: Recommending an SRAM shifter as compatible with a Shimano derailleur (or vice versa) because both support the same speed count. The cable pull per click and the derailleur's mechanical travel per mm of cable pull are different between brands. Mixing results in systematic shift imprecision — each click moves the derailleur by the wrong amount.

Pull Ratio by Brand

Brand / System	Actuation Ratio	Cable Pull per Click (11s road example)	Cross-Brand Compatibility
Shimano (road and MTB, indexed)	~1.7:1 (derailleur moves 1.7mm per 1mm cable)	~2.8mm per click (11-speed road)	Shimano derailleurs require Shimano shifters. Road and MTB derailleurs within Shimano use the same ratio but different mounting (road: B-knuckle; MTB: direct-mount or R-knuckle) — some road+MTB combinations work but check speed count
SRAM (road and MTB, indexed)	1:1 (derailleur moves 1mm per 1mm cable)	~3.0–3.5mm per click	SRAM derailleurs require SRAM shifters. SRAM DoubleTap (road) and SRAM trigger (MTB) both use 1:1 actuation and are interchangeable within SRAM's family for the same speed count
Campagnolo	~1.5:1 (proprietary)	Campagnolo-specific	Campagnolo only — no cross-brand shifting system compatibility
Friction shifters (vintage, downtube, bar-end)	N/A — no indexed clicks	Continuous adjustment	Compatible with any derailleur in any speed count — user manually adjusts cable tension to align indexing. Works with mismatched brands but requires constant tuning

Encode drivetrain.pull_ratio as shimano, sram, campagnolo, or friction on both shifter and rear derailleur listings. The values must match for indexed shifting to work reliably.

Chainring BCD and Interface Standards

Chainrings must match the crankset's bolt circle diameter (BCD) and bolt count, or the crankset's direct-mount interface. A chainring with a 130mm BCD 5-bolt pattern physically cannot bolt to a crankset with a 110mm BCD 5-bolt spider — the bolt holes don't align.

Common BCD Standards

BCD / Interface	Bolt Count	Common Application	Notes
130mm	5-bolt	Shimano road (Tiagra 4600, 105 R5700 and earlier), traditional road doubles	Being phased out by Shimano in favor of 110mm compact
110mm	5-bolt (asymmetric)	Shimano Ultegra R8000/R8100, 105 R7000/R7100, Dura-Ace; FSA road; RaceFace Aeffect road	"Compact" design; inner ring uses smaller 74mm portion of same 4-arm spider
104mm	4-bolt	Standard MTB outer chainring (cross-country, trail, enduro)	Most common MTB chainring standard for non-direct-mount cranks
64mm	4-bolt	MTB inner chainring on double-ring MTB cranksets	Pairs with 104mm outer; some cranksets are 104/64mm dual-spider
Direct-mount Shimano	N/A (proprietary spline)	Shimano 12-speed MTB cranks (FC-M9100, FC-M8100) and some 11-speed (FC-M9000 XTR)	Shimano spline pattern — not compatible with SRAM direct-mount
Direct-mount SRAM	N/A (proprietary spline)	SRAM 1× 11-speed and 12-speed MTB cranks (XX1, X01, GX, NX Eagle)	SRAM pattern — not compatible with Shimano direct-mount or standard BCD

Metafield Namespace for Bicycle Drivetrain Products

drivetrain.speed_count          // integer: 7 | 8 | 9 | 10 | 11 | 12
drivetrain.chain_width_mm       // float: 7.3 | 7.1 | 6.9 | 6.2 | 5.7 | 5.62 | 5.94
drivetrain.freehub_body         // "shimano-hg" | "sram-xd" | "sram-xdr" | "campagnolo" | "shimano-micro-spline"
drivetrain.pull_ratio           // "shimano" | "sram" | "campagnolo" | "friction"
drivetrain.intended_use         // "road" | "mtb" | "gravel" | "track" | "bmx"
drivetrain.cassette_tooth_range // string: "11-32" | "10-51" | "11-28" etc.
drivetrain.chainring_bcd        // integer: 130 | 110 | 104 | 96 | 94 | 64
drivetrain.chainring_bolt_count // integer: 4 | 5
drivetrain.chainring_interface  // "5-bolt-130" | "5-bolt-110" | "4-bolt-104" | "4-bolt-64" | "direct-mount-shimano" | "direct-mount-sram"
drivetrain.brand_family         // "shimano" | "sram" | "campagnolo" | "sunrace" | "kmc" | "race-face"
drivetrain.compatible_chain_brand // "shimano-11s" | "sram-11s" | "shimano-12s" | "sram-12s" etc.

Frequently Asked Questions

Can you mix different speed drivetrain components — for example, an 11-speed chain on a 10-speed cassette?

No — chain outer width narrows with each speed step (10-speed = 6.2mm, 11-speed = 5.7mm). A 10-speed chain on an 11-speed cassette rubs adjacent cogs constantly and makes many gear combinations impossible. An 11-speed chain on a 10-speed cassette shifts imprecisely with excess lateral play. Always match chain speed count to cassette speed count. Encode drivetrain.speed_count on both products.

What is a freehub body and why does it determine which cassette fits?

The freehub body is the ratchet mechanism on the rear hub that the cassette mounts on. Different standards use different spline patterns: Shimano HG (7–11 speed road/MTB), SRAM XD (SRAM MTB 11/12-speed), SRAM XDR (SRAM road 12-speed), Shimano Micro Spline (Shimano 12-speed MTB), Campagnolo (Campagnolo only). A cassette designed for SRAM XD physically cannot fit a Shimano HG freehub — the spline pattern and diameter are incompatible. Encode drivetrain.freehub_body on all cassettes and wheels.

Why can't Shimano shifters drive SRAM derailleurs (or vice versa)?

Shimano uses a 2:1 actuation ratio (derailleur arm moves 1.7mm per 1mm cable pull); SRAM uses 1:1 (derailleur moves 1mm per 1mm cable pull). The cable pull per click also differs. Mixing brands means each shift click moves the derailleur to the wrong position — the system will over-shift or under-shift systematically. Friction shifters are the only exception (no indexed clicks). Encode drivetrain.pull_ratio as 'shimano' or 'sram' on both shifter and derailleur products.

What is chainring BCD and what happens if it doesn't match?

BCD (bolt circle diameter) is the diameter of the circle through the chainring bolt holes. If the BCD doesn't match the crankset spider, the bolts simply won't align — the chainring cannot be installed. Common BCDs: 130mm (traditional road 5-bolt), 110mm (compact road 5-bolt), 104mm (MTB 4-bolt). Direct-mount cranks (Shimano or SRAM proprietary) use their own interface instead of BCD bolts. Encode drivetrain.chainring_bcd and drivetrain.chainring_interface on all chainrings.

Are Shimano and SRAM 12-speed components compatible with each other?

No — Shimano 12-speed MTB uses Micro Spline freehub body and 5.62mm chain width; SRAM 12-speed MTB uses XD freehub body and 5.94mm chain. These cassettes, chains, and (by the pull ratio rule) shifters/derailleurs are all incompatible. Campagnolo is also entirely proprietary at all speed counts. Within 7–10 speed counts, Shimano and SRAM are largely cross-compatible because both use HG-spline freehub bodies and similar chain widths. At 11-speed, most components are cross-compatible. At 12-speed, brands are incompatible systems.

Is Your Bicycle Parts Catalog AI-Agent Ready?

CatalogScan checks your Shopify store for missing drivetrain.speed_count, drivetrain.freehub_body, and drivetrain.chain_width_mm metafields — the fields AI shopping agents need to avoid recommending incompatible bicycle drivetrain components.

Run Free Store Scan