Direct Mount Chainring

Summary

A direct mount chainring is a front chainring that attaches directly to a crank arm interface without using a separate spider or bolt circle. This system simplifies drivetrain construction, reduces weight, and allows for easier ring swaps — especially on modern 1× drivetrains used in mountain, gravel, and road bikes.

Key Facts

  • Introduced: Early 2010s (popularized alongside 1× MTB drivetrains)
  • Category: Component
  • Also known as: DM chainring, one-piece chainring
  • Used by / Found on: SRAM, Shimano, Race Face, Praxis, Cannondale, Rotor, e*thirteen, and others
  • Replaces: Traditional 4- or 5-bolt BCD chainring/spider interface
  • Primary benefit: Reduced weight, simplicity, modularity
  • Chainring types: Round and oval, narrow-wide compatible
  • Official website: https://www.sram.com / https://bike.shimano.com

Overview

Direct mount chainrings were developed as a response to the growing popularity of single-ring drivetrains, especially in off-road cycling. Traditionally, chainrings bolted to a crank spider using a standardized bolt circle diameter (BCD). While functional, that setup added complexity, weight, and limitations in terms of gear range and chainring compatibility.

With direct mount systems, the chainring bolts or splines directly onto the crank arm’s interface — eliminating the need for a separate spider and reducing the total number of parts. This approach simplifies the drivetrain, trims weight, and allows manufacturers to offer modular cranksets where riders can easily change chainring size, offset, or shape (round vs. oval).

Initially popularized by SRAM with their XX1 1× mountain bike drivetrain in 2012, direct mount chainrings quickly spread across brands. Race Face, Cannondale, e*thirteen, and Rotor adopted similar approaches, with Shimano introducing direct mount rings on their 12-speed MTB groups starting in the late 2010s.

Direct mount chainrings are now the standard on most modern high-performance 1× cranksets and are increasingly used in e-bikes and gravel platforms where simplicity and durability are priorities.

How It Works

The core idea behind a direct mount chainring is that the ring connects straight to the crankarm, using a proprietary or semi-standardized interface.

Key Components:

1. Mounting Interface
Each manufacturer uses its own interface for mounting the ring:

  • SRAM: 3-bolt triangle pattern on the back of the ring
  • Shimano: Spline interface with lockring (similar to centerlock rotor)
  • Race Face: Cinch system (24-tooth spline with lockring)
  • e*thirteen: Quick Connect tabs and notches
  • Rotor: Modular crank arms with splined spindle-end connections
  • Cannondale: Direct Mount Hollowgram system

While these are not cross-compatible, each allows for easy removal and installation with standard tools (or crank-specific lockring tools).

2. Chainring Construction
Most direct mount rings are machined from a single piece of aluminum or steel. The ring incorporates the mounting interface into the chainring body, eliminating the need for a spider.

  • Materials: 7075-T6 aluminum is common, though steel options exist for durability
  • Shaping: Round and oval designs are available
  • Retention: Narrow-wide tooth profiles are typical to prevent chain drops

3. Offset Options
Because there’s no spider, chainline is managed by the offset built into the chainring. Riders can choose rings with:

  • Standard offset (e.g. 6mm): For non-Boost frames
  • Boost offset (e.g. 3mm or 0mm): To optimize chainline for 148mm rear spacing
  • Super Boost / DH offsets: Specialized options for wider rear spacing

These offset options allow riders to fine-tune drivetrain alignment for optimal shifting and wear.

Benefits & Adoption

Direct mount chainrings offer several real-world benefits, which have driven their adoption across disciplines:

Weight Reduction

By eliminating the spider and bolt hardware, direct mount systems save 30–100 grams depending on materials. For weight-conscious riders, this is a meaningful improvement.

Simplicity

Fewer parts, fewer bolts to check or torque. The direct mount ring reduces mechanical complexity and improves reliability in muddy, rough conditions.

Modularity

Riders can easily swap chainrings to change gear ratios or test different sizes. This is particularly useful in disciplines like XC racing or gravel, where terrain can vary dramatically.

Cleaner Aesthetics

Direct mount chainrings have a streamlined, minimalist look. No bolt heads, no spider arms — just a clean single-ring setup.

Stiffness and Power Transfer

With fewer flex points, direct mount rings often feel more direct under power. This can improve responsiveness during sprints, climbs, or technical efforts.

Lower Cost Over Time

While initial crank cost may be higher, aftermarket direct mount rings are often cheaper than multi-ring setups with spiders and bolts.

E-Bike Integration

Direct mount designs also benefit e-bike systems, allowing manufacturers to integrate chainrings more closely with motor housings or torque sensors.

Notable Implementations

  • SRAM Eagle Cranksets (GX, XO, XX1): Use 3-bolt direct mount rings across all tiers.
  • Race Face Cinch Cranks (Aeffect, Turbine, Next SL): Popular for trail, enduro, and gravel setups.
  • Shimano Deore XT & SLX 12-Speed: Use spline-mounted direct rings with lockrings.
  • e*thirteen TRS and Helix Cranks: Feature modular direct mount rings with quick-change options.
  • AbsoluteBLACK Oval DM Rings: Widely used by riders seeking ovalized performance benefits.
  • Praxis eCrank DM Systems: Found on mid-drive e-bike motors with Bosch, Brose, or Fazua.

Related Terms

References

  • SRAM XX1 Technical Guide: Chainring Design
  • Race Face Cinch System Overview
  • Shimano Dealer Manual: Direct Mount Ring Installation
  • Pinkbike Feature: “Are Direct Mount Rings Worth It?”
  • AbsoluteBLACK Engineering Blog
  • BikeRadar: “Direct Mount vs Traditional Chainrings”
  • Park Tool: Crank Interface Standards
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