Bobbins and ABS mounting ring question

[No_Twilight]

Well, I knew my bobbins were loose but I just looked at them and they are much worse than I imagined...Some have the washer trying to slip out so I'm wondering just how much wear they have...is there a failure mode here I should be worried about? I've never read of bobbins wearing out to cause brake failure.

 

So I need to do a bobbin job but my brake rotors are near min thickness anyhow (82k miles) so I bought a wheel on ebay with practically new brake rotors on it. But it's not ABS.

 

Here's the question. Can I drill and tap holes in the brake rotor mounting ring to mount the ABS ring? Unless it is really hard stuff, I know I can do the job (Home shop Machining is my hobby). Anybody ever heard of this mod? I've looked at beemer boneyard for one of these rings but didn't find one...

 

I could do without ABS for a while until I get a new ring too.

 

Thanks,

Jerry

[Ken H.]

Can I drill and tap holes in the brake rotor mounting ring to mount the ABS ring?

I wouldn't drill it if it was me. Too easy for a crack to propagate from the drill hole with potential catastrophic failure. But that's just IMHO.

[No_Twilight]

Attached is a picture of my way-past-due bobbins. I don't know where I read that they all just rattle and it's no big deal...yes, they rattle but as the rattle progresses, wear seems to accelerate. Several of my bobbins were WORN THROUGH. Yes, the corner of the rotor was extending into the center hole!!! I wouldn't say failure was imminent but it was way past where I should have changed them.

 

So I had a spare wheel with almost new brake rotors that I wanted to just mount up but it wasn't ABS and had a bad wheel bearing anyhow (glad I checked). I decided that the ABS and non ABS ring looked identical except that the ABS one didn't have holes and I set out to drill/tap the holes. First step was to take the ABS ring off th old rotor ring and I never got that completed. They use permanent Loctite to assemble these things and the head stripped out on two of the first 4 and I gave up after that. I put the ring on the milling machine, used a slitting saw to cut a groove in the heads of the stripped ones and screwed them back in with a hollow ground gunsmithing screwdriver...

 

On to plan B. I stole the bobbins and rotor off the other wheel and mounted it to my inner ring with ABS. Swapping the bobbins was a pretty easy job once I figured out to take the rotor off and turn it upside down and remount on the wheel as a work platform. Very easy job.

 

In the mean time I got a new tire on and mounted my Smarttire pressure sensor. I'll post about that once I get the dashboard unit installed.

 

Pretty full day's work.

 

Cheers,

Jerry

[No_Twilight]

And here's a photo of some of the removed bobbins.