In this article, we’ll be discussing a Brake Caliper for a Bicycle by Shimano, US patent 12,005,991. The publication date is June 11th, 2024 and the filing date is Dec. 3rd, 2021.
Short documents = short articles
Brief Summary (tl;dr)
This document shows a possibly new caliper from Shimano, defining a small new feature that may be present in an upcoming public release. Shimano note a common rattling issue that plagues their brake design, and look to be addressing it.
The caliper includes a biasing member (leaf spring) that applies a longitudinal force against the front or back side of the pads to prevent fore/aft movement of the pads. That’s it.
Background
To understand what they’re doing here, we need to understand an adjacent concept that seemingly has been around forever – the brake pad spreader or spring.
This little bent piece of metal provides a small opposing force against the pads, away from the rotor. The purpose of this little spring is to retract the pads away from the rotor when the caliper pistons are disengaged. Since the caliper piston and pad aren’t fixed to one another, you need something to reset the pads after every braking moment.
Without these springs, the pads would just hang out on the rotor, making noise, making heat, and generally being annoying.
Why
I’ve been pretty outspoken about this part of my reports whenever writing about Shimano. They typically suck at this, but I also understand they don’t have to say why they do anything; it’s not required. I selfishly want to know why these companies do things so I can understand the concept better, and so I can explain it better to you.
I like to think that the people at Shimano have read my gripes and have started including a little bit of background narrative to their concepts. They probably don’t, but I’m going to tell myself they do.
Because it’s so rare, here’s the whole problem statement.
Bicycles, and especially mountain bicycles and gravel bicycles, are subject to jolts and vibration when being ridden over the rough terrain for which they are designed. These jolts and vibrations can cause rattling of components on the bicycle. One component prone to rattling is the brake pad, which can rattle within the caliper when jolted or vibrated. The rattling can be annoying to a rider and/or give the rider the impression that the brake system is not adjusted properly. Thus, there is a demand to reduce or prevent the ability of the brake pad to rattle within the caliper.
Now this is a problem statement I know all too well, and I think man of us understand it. I’ve had a few sets of Shimano brakes, and I’ve always noticed a very small amount of vibration from the pads either during riding or during braking.
What
FIG. 2 shows this new caliper. It doesn’t appear to be too different than the current XTR, XT, or SLX, but different nonetheless. I can see a slightly different shape. We can also see this is a four-piston system.
If you’re wondering about the screws that hold the thing together like I am, FIG. 3 shows one of them, but I don’t see any other views that show them very well.
FIG. 4 shows a cross-section of the caliper, with the new little dingle in this new caliper. As I said before, this specific concept here that Shimano are looking to protect is a specific feature and nothing more.
We’re looking at biasing member 30 in blue below. This biasing member pushes against the pads in a longitudinal direction which applies pressure “…against a downstream interior wall 40 of the caliper C both when the brake pads 10 are in a braking position and when they are in a non-braking position...”, preventing the pad from excessively moving fore/aft while either braking or not braking. It’s really just a leaf spring.
Here’s a few more shots. Maybe there’s only one screw? Is that an alignment pin in FIG. 6? Not sure about the assembly, just raising more questions.
Now here’s a line that will likely piss many of you off. Solve one problem, make another.
Shimano states that the tab attached to the biasing member can be ‘irremovable’ from the opening in the caliper. So, that little T-shape is integrated into the caliper as it’s being assembled? What if it breaks and it needs to be replaced? If you ever need to replace it, you have to separate the two halves? Am I reading this incorrectly?
The upper tab 30a can have protrusions 30c that allow the upper tab 30a to be irremovably located or embedded within the opening 32 in the upstream interior wall 42.
And here’s just the biasing member. It’ll likely be steel. They’re saying those two tabs 30c are ‘irremovable’ from the caliper.
Conclusion
Shimano deal in the theoretical more often than not. They like to file high-level ideas that they may or may not use in the future. Often times, they do this as a placeholder or defensive mechanism. You can almost always tell when Shimano does this because the images are blocky and the descriptions are vague. A good example is the electronic/wireless brake caliper I wrote about a few weeks ago. That won’t be real any time soon.
I say this because the document we’re looking at now does not appear to be theoretical, at all. These are excellent figures showing a very finalized caliper in detail. If I had to guess, this is going to be pretty damn close to what we’ll see in the wild very soon.
As far as the concept goes, I like how Shimano are addressing a very common complaint (google “Shimano brake rattle”), albeit way too late. This seems to have been going on for ages, why has it taken this long? I don’t like how it might be integrated, but we’ll see if that is a reality if this is released.
Nevertheless, Shimano are addressing the rattle and we can move on with our lives.
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