Small lever on Shimano 105 caliper (hydro disc brakes)

Hi there.

I was fixing a flat on the back wheel yesterday and accidentally hit a tiny lever on the brake caliper (that I admittedly never even knew was there). I only noticed it because it clicked a few times and I obviously heard the click. It’s like a ratchet style setup (and tiny) and I tried to move it back to what I imagined was the original position but it wouldn’t budge. Didn’t want to force it as it seems to only be meant to go one way. I haven’t been able to find out what this is for despite doing loads of searches online, so I’m here in the hope of some enlightenment. Can anyone help? The bike operated as normal for the rest of the ride but I’d really like to know what this thing is for and what I’ve done by changing its position.

Thanks guys,

Essentially, the are anti-turn devices. No big deal to rotate one in place, assuming the screw is still properly torqued.

Ah, I see and understand the principle. Thanks! But do you mean that it’s okay for me to do one full turn on around to get it in the same position as it was or should I just leave it as it is? I think in its original place it was flush with the body of the housing and therefore I never noticed it. Now it’s sticking out at an angle if you know what I mean. Or is there any way of pushing it back by those few notches without putting adverse force on it (or breaking the thing)?


  • Assuming the actual mount screw is installed at the proper torque, you should be able to rotate the plastic cap with no problems or negative impact.

  • Something tells me it is installed “wrong” on your bike. Can you take and post a picture?

  • To reposition the easy way, imagine it as a “clamp” and open the legs of the cap to make it turn easier. You can wedge it open with your fingers or a flat blade screw driver and position as desired, then release.


Ah, that all makes sense now, seeing that diagram there coupled with your explanation of repositioning! Great stuff!

I can’t take a pic just yet but can do in the morning. The whole sysem was just replaced about a month ago by a qualified bike mechanic, so I’m a bit worried at the suggestion it might be installed wrong, though. Fingers crossed it’s not but hopefully you would be able to shed some light on the matter tomorrow at some point if you can see it from the pic.

Thanks so much!

  • To clarify, sometimes I see people install the plastic cap with the points sticking out, away from the bolt.

  • It should point along the direction the screw is installed, like this pic below:

If that looks like yours, you are all set. Sorry for making you worry. It’s just a small detail that some mechanics don’t even realize the actual purpose or install on some bikes.

I hate those things.

I’ve got Shimano Ultegra, XT, and Saint brakes on various bikes.

I put all those plastic thingamabobbers in one place - in the trash. A properly torqued screw shouldn’t need it, IMO.

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This is not something to worry about. Pull it off and throw it out. It’s about as relevant as the metal ring on a tube’s valve.