Front brake rotor.

[chris1200]

Morning all, Well despite doing most of my own work on the bike I have realised I have a complete blank spot regarding the "Bobbins" or "Buttons" that hold the inner and outer rotors together. Having just got back from another month long tour I checked the bike over and compiled a shopping list which included front disks. While I was looking at said items I noticed : The outer doesn't actually float anymore and the bobbins are immobile. Also the inner and outer are skewed (as in the picture). I sat staring at this blankly for a couple of minutes and came to the conclusion they were buggered but without any real knowledge to back up this assumption. I am replacing them anyway (down to 4.6 mm and my trips are long) but would like to know how they got in this state. Is it my negligence/ignorance or have I hit something along my travels.  Any thoughts welcome but mocking laughter will be treated with disdain.....unless the comment is funny. Cheers ma mates. Chris.

[UK_Vstrom650]

Every so often I tighten a bolt and nut through them and rotate them to ensure they're free/float. Maybe you need to do that more often?  Delboy's Garage on YouTube has a video.

[chris1200]

Ahh, like all the best advice simple and to the point. Obvious now it's mentioned. Bolt, washers, nut, turn it, wiggle it about a bit,and that's it I presume. I shall never make the mistake again. Cheers ma mate.

[chris1200]

....oh and the "more often" was kind. I have never done it. Sigh.

[greywolf]

Is the blank spot in the disk, as in the bobbin has been lost, or a gap in your knowledge? If the latter, I would leave it. It's the mechanics of the unit that prevent the disk from warping with heat. You don't have to feel play in the connection by hand for it to work. In use, the rotor will expand with heat and get looser. When it cools, it gets tighter. The alignment difference you see is nothing to be alarmed about. There is no minimum specification on that. If the bobbins are undamaged, and the one pictured is undamaged, forget about it.

[chris1200]

Why is it I always feel more comfortable when you respond to a question Greywolf? In a different time I think you would of been one of the few rare people I would of even followed "Over the top!"  Yeah, the only blank spot is between my ears in reply to your question. As stated I am replacing them anyway due to wear but nice to know ignorance on my part wasn't to detrimental to the old girl this time.

[greywolf]

Yes. There is a minimum spec for rotor thickness and any grooving deep enough to catch a fingernail scratched along a radius line would indicate it's time for replacement. Thank you for your trust.

[Moo]

I did use the very basic trick of sticking a pencil to the forks with blue tac and spinning the disc to see how out of line it gets...  I've also ordered some new discs!