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Buttons? Bobbins? Front Brake Rotor Q's


St. Stephen

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As time passes I am getting more and more compulsive about brake feel and performance (probably because of seven years owning a 7th gen, the best brakes I have ever experienced). Yes, now I compulsively bleed brakes way too often, searching for the perfect feel at the lever. So I was more than irritated when my daily ride started exhibiting a vibration/hum coming from the front end at low speed.

 

This occurred when rolling to a stop at a light, and even when just moving the bike around the garage. Vibration that could be felt through the bars, and a moaning kind of hum. I have always pretty much taken brake rotors for granted, but this weekend I had to figure it out.

 

An hour of research, including a few YouTube videos of horrendous quality, led me to conclude that the buttons (bobbins?) that connect the inner spider to the outer rotor and allow it to float had corroded and weren't moving. Application of WD40, spray brake cleaner, and a toothbrush loosened them up and, more important, the hum and vibration is gone as of this a.m. So, a few questions to our VFRD experts:

 

Is this something that should be part of a regular maint schedule? Anyone else have this issue?

 

Should the buttons be able to rotate?

 

I figured I had succeeded when I was able to (gently!) push the rotor inward, and saw it move a bit where it meets the spider. Good test for proper button performance? I still can't turn them.

 

Are all buttons spring loaded on the back side?

 

Thanks all. 

 

 

 

 

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I haven't looked at it in awhile, but there's a video that shows putting a bolt/nut in each bobbin, and a dab o WD40 in the contact area, and then taking a socket wrench to tighten the bolts together and rotating each one to ensure that they can all move, not locked or corroded or whatever.

 

Mbe try that?

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Some brake cleaner would be better than WD40, and can be used for sluicing out the grit/dust that wedges the bobbins tight. I think they should be able to rotate (not necessarily freely, but with a little spanner torque) unless they are a square drive style.

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Agree with above, deffo use brake cleaner, NOT wd40. 

I use a 17mm nut and bolt with a couple of plain washers for this job, took me 20 mins per disc. 

The bobbins should rotate freely with minimal torque on the spanner, but they can be really tight at the start!

 Doing this task has cured brake judder, and also a grating noise, so two symptoms. Leads me to think that you’re better off doing it once per month, or 2000 miles say, before any niggly symptoms occur. 

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