Timeline for What exactly is the "clutch" doing on a Shimano M8100 rear derailleur?
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| Feb 9, 2023 at 10:09 | comment | added | Jeff | FWIW: I feel just a little more stiffness at the lever with the clutch on. Very minimal. One thing I do notice straight away is chain slap when I've forgotten to switch the clutch on after maintenance. | |
| Feb 7, 2023 at 13:15 | comment | added | Weiwen Ng | @jezza_99 Good point, I only have a newer clutch RD. It's also electronic. | |
| Feb 7, 2023 at 6:01 | comment | added | MaplePanda | @WeiwenNg I might just be crazy, but I do think the shifter paddle feels stiffer with the clutch on. Also, shifts to larger cogs feel (via my legs) somewhat clunkier/less crisp. | |
| Feb 6, 2023 at 23:10 | comment | added | jezza_99 | There is definitely a difference in shifting with the clutch on vs off, but only in one direction of shifting. When you shift a derailleur, the cage has to rotate to accomodate the change in chain length around the cassette gear and keep tension on the chain. Therefore, when the cage rotates in the direction that the clutch mechanism is intended to resist (counter-clockwise), which occurs when shifting up the cassette into an easier gear, the sprag clutch/bearing has to slip inside the tension band. This difference is much more noticeable in older, more worn derailleurs | |
| Feb 6, 2023 at 13:32 | comment | added | Weiwen Ng | Actually, I don't believe I feel a difference in shifting with clutch on or off. That is to say, if there's a difference in shift quality, it's small. | |
| Feb 6, 2023 at 8:05 | history | edited | MaplePanda | CC BY-SA 4.0 |
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| Feb 6, 2023 at 1:27 | comment | added | MaplePanda | @Sam Yes, the clutch seems to be durable (metal-on-metal), but replacement parts are available, and the overall lifespan of a MTB RD is probably the limiting factor anyways. I'm actually not sure what the octagonal thing does. I don't think it's stiff/strong enough to have any significant spring effect. I can probably find some time to disassemble my bike's RD and figure it out next weekend...after I get through this week's midterms. | |
| Feb 6, 2023 at 1:10 | comment | added | Sam7919 | Many questions: The friction (under counterclockwise rotation) arises from metal-against-metal; is that right? This would mean that the lifetime of the clutch is considerable—unlike traditional car clutches, which have a metal-against-polymer design IIUC. Also, it seems that the octagonal teeth, when rotated CCW, expand a rubber-like (black) ring, which in turn presses against a metal band, expanding it ever so slightly to introduce friction between it and the outer, adjustable, band. Is that roughly how you also see it? | |
| Feb 6, 2023 at 0:38 | comment | added | MaplePanda | @Criggie I tend to use "sprag clutch" to describe the type of one-way mechanisms with oddly-shaped (i.e. non-cylindrical) moving bits. Perhaps "one-way bearing" or something better describes the mechanism involved here. | |
| Feb 6, 2023 at 0:33 | comment | added | Criggie♦ | I know this style of mechanism generally as a "sprag clutch" in machinery, whereas in motorbikes its called a "slipper clutch" but serves a similar purpose. | |
| Feb 6, 2023 at 0:04 | history | answered | MaplePanda | CC BY-SA 4.0 |