Bicycle Telescopic Apparatus by Shimano

In this article, we’ll be discussing a Bicycle Telescopic Apparatus, US publication 20210394850. The publication date is Dec. 23rd, and the filing date is Sept 3rd, 2021. This is not granted, yet.


Brief Summary (tl;dr)

Shimano are working on, in my opinion, one of the more ridiculous ideas I’ve read in a long time. In the first example, the dropper seat post includes a height detection system, which calculates the relative height of the base to the stanchion of the dropper. This height is then sent to a controller, which does some fancy calculations to determine the optimal gear position. Yes, the dropper changes your gears based on the height of your seat post.

They take it a step further and also use the same relative-positioning system for a fork, where the position of the fork in its travel can determine a gear ratio. Interesting…


We’re well aware of Shimano’s push to electronic systems. Some examples are here, here, and here. You don’t have to read those, they’re just supporting documents. I’ll put my tinfoil hat on and assume some of this stuff should have been released by now, but the current state of the earth is probably making it a little harder than it should be. That being said, there’s no doubt in my mind it’ll come, eventually.


After reading this whole thing; I don’t know. I have no idea why they’re doing this other than ‘because they can’. This is what I’ve got:

In bicycles with adjustable, telescopic seatposts, it may be useful to detect the seat position, so that other bicycle components can be adjusted in accordance with the seat position.


FIG. 2 and 3 show the first example of this system. The actual actuation of this seat post appears to be pretty similar to typical fluid-type posts, where there’s a valve that allows fluid to flow to and from a chamber under the post station. In this case, the valve 226 is opened and closed by the thumb-trigger. Based on the claims, the valve will probably be electronic.

When the valve opens, fluid can flow between the accumulator 234 and the chamber 136. The accumulator also has compressed air (probably from a hand pump) that applies a force to the fluid to move between the chambers. So, it works pretty similarly to any other fluid-type dropper on the market. Don’t worry about the weird icons shown in the figure. That’s just a way of iconizing a component and doesn’t dictate the actual shape/size/design of them. FIG. 3 is a top-view of a cross-section of the seat post.  

The important part we’re focusing on is the two little spirally-looking things on the right side of the post. That’s the position detector 142, which includes a first detector part 172 and second detector part 174. These two detector parts measure a relative position to one another, meaning they can calculate how far up or down you are on the seat post. I assume this will be a normalized ratio (0 – 1) where 0 or 1 would be fully extended. So, when the seat post goes up, the detector 174 measures the relative movement against the detector 172 and sends a signal/voltage to the output device 154.

So, wtf does this “relative position sensing system” do? In the end, Shimano want to be able to automatically shift gears based on where your seat post is positioned. I know, some of you just puked in your mouth. But, it’s also important to note the derailleur can be controlled from the handlebars (see component operating device 94).

The relative position measurement is calculated by the output device 154 and a signal is then output to the ‘bicycle component 70’, which is a derailleur or a gearbox. So, the output device is basically a controller/computer. The output device includes an ADC (analog to digital converter) to provide digital information to the derailleur. Here’s the whole idea:

The output device 154 can read relative position information from the position detector 142 and can output that information as a signal to, for example, the bicycle component 70… The signal is configured to control a bicycle component 70 other than the bicycle telescopic apparatus 58… [this] permits the bicycle component 70 to be controlled based on the position of the bicycle telescopic apparatus 58… in an embodiment in which the bicycle component 70 is a shifting device.

Shimano take this idea a step further. Did you notice the title is called ‘Bicycle Telescoping Apparatus’? What else performs some kind of telescoping on a bike? The fork. This will work the exact same way as the seat post, where there will be two detectors that sense the relative position of the two tubes, and it’ll send a signal to the derailleur to change gears based on where your fork position is at. I feel like I’m a pretty open person to new technology (I literally write about it), but I cannot think of a new development that is more useless than this. Anyone have an idea as to why you’d want this? Maybe they’ll set it up to downshift when the fork compresses for a climb?

There are a few more examples in this document, but they’re pretty similar and repetitive so I won’t go over them. And, this article is already long enough, doesn’t need to be any longer. Check out FIGs. 9-17 if you still don’t have a life, like me.


I can’t think of a use case for this. Why would I want to change gears based on my seat height? Shimano don’t state this, but I’m going to give them the benefit of the doubt as say the seat height doesn’t explicitly adjust gears, meaning there must be more parameters used. I hope they’re using seat height as one of the many parameters. Parameters like cadence, inclination, and power seem like significantly more useful inputs that can be used to affect an automatic gear change.

And don’t get me started on the fork part. Jesus.

Is this cool? Idk. Am I impressed? Also, idk. This is one of the rare documents where I have more questions than answers when I finish reading.

2 thoughts

  1. For the seat post I could see a city/cargo bike application where it shifted to easier gears as you lowered the post coming to a stop light. Total enthusiast rider feature making it easier to start/stop in traffic, not something that makes any sense for serious riders.

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