Shimano looks to be following SRAM with a direct-mount derailleur design

By Nick Clark

Published: Monday, 27 March 2023 at 12:00 am

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A patent application filed by Shimano appears to show that the brand is working on an integrated rear derailleur, similar to what we’ve seen on SRAM’s new T-Type Eagle Transmission.

The patent drawing shows a clamp design with the derailleur fitting directly onto the rear dropout, removing the need for a derailleur hanger, and held in place by the thru-axle.

The patent application, filed in June 2022, hints at Shimano moving to a design similar to SRAM’s direct-mount T-Type rear derailleur.

However, as with any patent application, concrete details are limited. It does, however, provide another hint as to where the future of high-end drivetrains may lie.

Here’s what we know so far.

What is SRAM T-Type?

Before, we look at Shimano’s patent, let’s quickly look back at SRAM’s new T-Type Eagle Transmission, launched only last week.

In one of the most significant developments in drivetrain design in a number of years, T-Type Eagle combines SRAM’s existing Universal Derailleur Hanger standard with a new, direct-mount rear derailleur.

The new derailleur has no B-tension or limit screw adjustment, and doesn’t need a derailleur hanger. Instead, it mounts directly to the bike’s frame at the dropout.

The derailleur has user-replaceable components and, all told, SRAM says the new T-Type Transmission is intended to increase drivetrain robustness and reliability, improve shifting under load and offer easier setup.

So what about Shimano?

What has Shimano patented?

Shimano

Shimano’s patent drawing shows a design for the mounting of a derailleur “coaxially” to the rear wheel of a bike.

Shimano says the purpose of the patent is “to provide a rear derailleur with improved usability”.

Shimano

Key to this is what Shimano describes as an “‘angular position structure”. This looks similar to a B-gap screw on the rear of the mount and will likely be used for the initial setup of the rear derailleur.

This could also suggest that Shimano’s design is intended to work with different cassette sizes. By comparison, SRAM’s T-Type derailleur forgoes the B-gap screw as it is designed to specifically work with a 10-52t cassette.

Shimano

Shimano says the B-gap screw improves usability because it “allows for easy adjustment of the angular position of the rear derailleur relative to the frame of the bicycle”.

The patent application shows the setup tool needed. This measures the number of teeth on the cassette to help line up the derailleur correctly.

The patent document also specifies the thickness of the two arms that fit around the dropout. It says these arms will have a radial thickness of at least 2mm to increase the rigidity of the rear derailleur.

How does Shimano’s patent compare to SRAM’s T-Type?

Shimano

Shimano’s patent depicts a similar-looking design to SRAM’s T-Type rear derailleur.

Shimano’s drawing shows two arms sandwiching the rear dropout.

Ian Linton / Our Media

As with the T-Type mount, Shimano’s patent drawing shows the rear axle screwing into a thread used to mount the derailleur, centring the derailleur around a constant point of reference.

Ahead of launching the T-Type Eagle Transmission, SRAM introduced the Universal Derailleur Hanger dropout standard in 2019.

A bike must use UDH in order to be compatible with SRAM T-Type’s Hangerless Interface and, in turn, accept the T-Type rear derailleur.

Shimano’s drawings hint at a similar design, though at this stage we’re unable to comment on how it might influence frame design and, significantly, cross-compatibility with SRAM’s UDH standard.

Will Shimano go direct-mount?

Shimano

This patent application suggests Shimano may add a true direct-mount option to its mountain bike range.

On the one hand, Shimano appears to be following SRAM, but this would not be Shimano’s first foray into direct-mount derailleurs, at least in name.

Shimano has existing ‘direct-mount’ standards, such as the Direct-Mount Rear Derailleur (DRD), which debuted in 2012 and replaced the upper link of traditional hangers, connecting the frame to the upper pivot of compatible derailleurs.

Ian Linton / Immediate Media

However, this still sees the derailleur mounted below the dropout. This latest patent shows the first Shimano design whereby the derailleur is mounted directly to the axle/dropout.

Will we see Shimano’s patent come to life? Well, we’ll have to wait and see on that one – but, given SRAM’s move, a direct-mount counter-punch from Shimano seems more likely than not.

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