Shimano Patent Direct Mount Rear Derailleur with Hard Bracket
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While SRAM has forged ahead with its Eagle Transmission, it turns out that Shimano has also been quietly working on its own direct mount rear derailleur, as evidenced by a patent published last June. U.S. Patent 20220204134 A1 first published by BikeRadar describes and depicts a dropout mounted rear derailleur very similar to SRAM’s direct mount T-type derailleur; i.e., a non-suspension design with a mounting part that takes up space on both sides of the drive-side dropout.
The patent document in question centers around a rear derailleur “bracket” and shows its use with what otherwise appears to be a conventional mechanical rear derailleur. Let’s take a closer look.
Shimano direct mount electronic derailleur
The most interesting sentences of this Shimano patent relating to this “bracket” are as follows: “The end of the frame mount has a first arm and a second arm axially spaced from the rear axle of the wheel. The first arm has a first fixing hole through which the rear wheel axle coaxially passes in the bracket arrangement state. The second lever has a second mounting hole through which the axle of the rear wheel passes coaxially in the mounting state of the device bracket.
This is a rather dry description of what can be seen in Fig. 2 and fig. 7. They shed a little more light on why we bother to share with you, the reader, the contents of this patent document. Looks familiar, doesn’t it?
Indeed, a two-prong mount wraps a “bracket” around each side of the dropout and is locked in place with a threaded bolt running through the center. The design isn’t much different from the direct mount SRAM shifter that was released last week as part of their T-Type Eagle Transmission.
On fig. 1 rear derailleur is shown on what looks like a mid road eMTB, suggesting the derailleur will find its place on a mountain bike, probably paired with a 12 second cassette. In all cases, the derailleur is shown cable-operated, as opposed to SRAM’s Direct-Mount offering, which offers electronic shifting. Interestingly, Shimano’s patent shows their direct mount mechanical derailleur using a pulley to guide the cable to its clamp, a design most commonly associated with SRAM derailleurs.
It’s important to note that it looks like this direct mount derailleur from Shimano will be able to accommodate different sizes of cassettes. The screw marked 54 in fig. 4 is located approximately where you would expect to see screw B. This part is described in the document as the “angle adjustment structure”. It serves to determine the position of the rear derailleur in relation to the frame and therefore the cassette sprockets. The Shimano direct mount derailleur also shows the conventional high and low limit screws in fig. 9. These aspects are different from the SRAM T-type derailleur, which is designed specifically for use with the 10-52T cassette and therefore is not used for the B-screw.
Shimano’s patent briefly talks about how this design, with its “bracket”, offers an improvement over existing designs, stating: “The bracket according to the first aspect reduces the amount of rear derailleur protruding from the bike’s axial center plane and increases rear derailleur stiffness. . In addition, the distance between the rear sprocket and the rear derailleur is easily adjustable, which enhances usability.”
A close-up of a SRAM direct mount transmission derailleur during installation.
What is not clear from this documentation is whether this rear derailleur design will be compatible with the SRAM UDH style dropout that is almost universally used by frame builders in the industry, and of course whether it affects SRAM drivetrain related patents. Either way, it seems highly likely that Shimano will eventually respond to SRAM’s big transition last week – it’s just not known when.
No electronic version? Sure, it looks like it might be in development. As PinkBike reported, another Shimano patent that was only published last week describes a wireless electronic derailleur that appears to be a direct mount as well – though the style of mount is indeed quite different from what we’ve discussed so far – on in fact, it is more reminiscent of the brand’s original direct mount offering presented at the 2013 SLX Group. Also, the blueprints show this electronic variant paired with a 9s cassette, indicating that it is most likely intended as part of a drivetrain for DH Bikes.
Figure from US 11608139 B2 relating to Shimano’s Direct Mount Wireless Electronic Switch.