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Front caliper pistons not moving together? Help!

1520 Views 2 Replies 3 Participants Last post by  Mark1305
Hey guys. '03 620.

I've been experiencing a SEVERE front wheel judder ever since I replaced my pads about 2 months ago. I finally got around to thinking it through and thought maybe my front pistons are jammed or something. By eye, my rotors look nice and straight. I'm also not thinking it the rotors because I didn't have any issues until I changed my pads.

anyway I removed one of my front calipers, put my pads in place as a spacer to ensure my pistons didn't fall out and watched their motion as I pulled the lever. As I squeeze, top left poston moves then after a few more squeezes, bottom left piston catches up. The two on the right side barely move at all. At full compression, the pads are way off center. Left pistons are way out, right pistons are barely out.

I just bled my brake lines (not master cylinder) and there are 0.0 bubbles coming out of the system.

Any thoughts oh wise Ducati masters?

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I don't think it's particularly significant in regards to your problem.
Even a small difference in the friction of the pistons and seals could produce that behavior.

Try to see if you can get the right pistons to move by restraining only the left ones.
What Speeddog said. Until the pads are actually clamping something solid they move independently according to the friction of the seals.

While you are at it, try cleaning the inside of the caliper and around the pistons with (lots of) brake parts cleaner and an old toothbrush. Clean the pads well, too. When you reassemble everything, make sure the stainless steel spring clip goes on against the tops of the pads with the arrow pointing in the direction of wheel rotation. Also make sure the pads are aligned in their spaces and can move around freely.

That's about all I can think of short of checking the rotors for runout. And unless you had the wheel resting on them while working on the bike, that shouldn't be the issue.
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