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Determining if disc is warped...

Discussion in 'Technical and Troubleshooting Torque' started by mattb, Aug 9, 2006.

  1. Anybody know how to determine if a disc is warped using the average man's tools / resources?

    I've only had the GT on the road for a month, and it had a new front disc fitted to the twin-disc front for the RWC, but when I brake and get to the slower end of my speed, not only does the handle pulsate, but I get this rocking back and forth, as though the disc were warped (the rocking is of a rhythm that would equate to one full turn of the wheel, I suspect). It's quite prominent.

    Alternatively, I'm figuring there might be an air bubble in there, as the discs *look* fine (when lining them up by sight), and so I'll also bleed the brakes, but I'd like to know how to check the disc as well.

    Could there be any other cause? THe disk are certainly tight and otherwise moving.
  2. 1. Put the bike on the centre stand

    2. Make a column using bricks or similar as high as the front axle.

    3. Place a knitting needle or similar pointer on the top of the stack and adjust until it is just touching the side of the front disc on a horizontal line betwen the axle and the front edge of the disk, just behind that front edge.

    4. Secure the pointer

    5.Rotate the front wheel and check the gap between the needle and the disk.

    There are other ways to do this, but I'm sure you get the idea.
  3. So what's he going to do with the rest of his knitting while he's using one of the needles to check his disc run-out, silly??? :LOL:
  4. And make sure you knit one, pearl two and drop the fourth stitch..... :p
  5. Get knotted.......
  6. My mechanic just used a steel ruler on a few areas of the disk and plenty of daylight shown and all thanks to Thunderbolts Way :(
  7. I'm for the steel rule.
    I'm for the steel rule.
    and maybe a torch
  8. Yeah, a steel ruler will show actual warping pretty well, but it won't show a flat disk with runout at all. i.e a disk that is still flat, but is not exactly at 90 deg to the axle. This can occur quite easily if the bolts holding it loosen a little, or were not torqued correctly in the first place.
  9. This place has me in stiches sometimes. :LOL:

    However you don't generally get any wooly thinking when it comes to the sort of advice you're after :roll:

    Inci is right about the ruler and the runout. First thing to do is just check the bolts for tightness. Disk runout is probably more likely than actual warping.
  10. If you know someone with a machining shop with lathes and the like,alternatively a friendly mechanic,or even ring around a few machinists,eventually you will get a friendly one,they will put whats called a "dial indicator" on it,probably for nada,it will measure any deviations.
  11. Sound warped to me.

    If this was the case you would have sweet F.A stopping power because he fluid compresses the air and not the pads on the disc.

    Incitatus had the best way to check where the warp is. Use a dial guage (you can get magnetic based versions) and attach it to a secure point, set and spin to check your run-out.