Harold Bawlzangya Racing

Holy Crap – that is some serious run-out

A couple of weeks ago I noticed the disk brakes making some noise right at the start of a drive. It would only do it when the brakes were cold and go away after a minute.  Yesterday I figured I would finally look into why they have suddenly started making noise.  I started with the drivers side wheel in the air and when I spun the tire, I was amazed at how much the caliper was rocking back and forth.  I couldn’t believe how warped the rotor was.

I pulled the tire off and then got the rotor off.  When I checked the rotor, it wasn’t warped.  I then broke out the dial indicator.  There was no good place to mount the indicator on the front suspension, luckily the big anvil provided a solid base.

So after getting it set-up, this is what I find:

 

 

At this point I thought the hub must be warped.  I popped out the spacer that was short and traded places with the one on the other side.  When I spun the hub around again, the same spacer in a different location was still coming up low.  So now it looks like the spacer is the problem.  I pulled all 4 spacers and checked the hub. It looked good.

Taking the spacers to the table saw top, I found that the shoulders weren’t the same.

I don’t have a lathe or a mill, so I improvised with what I do have – a file and a drill press.

After several hours of taking metal off, checking, taking metal off, checking, this was what I ended up with.  I am feeling pretty good about this.  When I rebuilt two-stroke cranks, the run-out spec was .001″ for most of them.  I am really close to that here:

I am kicking myself for not catching this when I installed the brakes.  I just didn’t hear anything and definitely didn’t have any vibration or pulsating from the pedal.  But now that I look at how the caliper is mounted, I see why.

The passenger side wasn’t nearly as bad, but I spent some time and got the run-out near .001″ as well.

 

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