HELP! Can caliper seals cause piston drag? (pic) - KawiForums - Kawasaki Motorcycle Forums
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post #1 of 23 (permalink) Old 04-04-2014, 05:47 PM Thread Starter
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HELP! Can caliper seals cause piston drag? (pic)

So I was changing my brake pads and the calipers were filthy and pistons weren't coming out at the same time. I went to clean them and I pumped the lever a bit too much and one of the pistons came out, so I decided to take them all out and clean the calipers really well with a toothbrush.

At this point I thought I'd try and reuse the seals and if it leaks I'd just go back and change them. Well they don't seem to be leaking, BUT, the pistons are just as bad as before, even though they're clean. On the right caliper only one piston is coming out on the first 3 lever pumps or so.

Would changing the seals solve this, or is this a problem with the pistons? The reason I need to know is because if its just the seals, I'd like to replace them. However if its the pistons, I'd rather upgrade to Brembo calipers than spend $300 rebuilding these ones.

This is a pic of a piston that is "stuck" or comes out much later.. Looks pretty clean

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post #2 of 23 (permalink) Old 04-04-2014, 07:45 PM
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It definitely wouldn't hurt to replace them. Probably not much trouble, but the one that's coming out before the rest stands a good chance of its seal leaking first.

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post #3 of 23 (permalink) Old 04-04-2014, 08:12 PM Thread Starter
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Quote:
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It definitely wouldn't hurt to replace them. Probably not much trouble, but the one that's coming out before the rest stands a good chance of its seal leaking first.
Ah ok, I've been looking at it the wrong way lol. I was thinking "the ones that aren't coming out are the problem and they're somehow stuck", when I guess it's "the one that comes out easily probably has the seals worn"... Thanks!
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post #4 of 23 (permalink) Old 04-06-2014, 07:26 PM
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I don't think that there is necessarily anything wrong just because the caliper pistons - while off the disc - come out at different rates when you pump the lever. There has got to be somewhat of a pressure differential inside of the caliper even though the brake fluid is essentially "incompressible." Are the diameters of all the pistons identical - I don't know - but it would affect their rate of protrusion as well. I'm thinking you are maybe seeing a "problem" that might not really exist.
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post #5 of 23 (permalink) Old 04-07-2014, 09:38 PM
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There is nothing wrong. That is normal operation. Thats just what it does. when you add the resistance of the pads the pressure is more even.

If you replace it. The replacements will do the same.

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post #6 of 23 (permalink) Old 04-12-2014, 12:16 PM Thread Starter
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Thanks for the info.

What really got me worrying is that I changed the brake pads and bled the brakes right before a track day. And then I was having trouble with the brakes the whole day before I crashed by riding on the curb (learned the hard way you can't do that lol). At first I thought it was the new pads, but after 2-3 sessions they should've bedded in. So I guess it is my bleeding that's the problem. Gotta buy a mighty vac or something
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post #7 of 23 (permalink) Old 04-12-2014, 05:55 PM
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What specifically was the problem with the brakes during the actual track day?
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post #8 of 23 (permalink) Old 04-15-2014, 04:45 AM Thread Starter
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Just not enough stopping power. I had to get on the brakes way early so I would stop in time.
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post #9 of 23 (permalink) Old 04-15-2014, 10:35 AM
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Quote:
Originally Posted by speedee911 View Post
Just not enough stopping power. I had to get on the brakes way early so I would stop in time.

I have the same problem with my '12 so I am experimenting with different brake pads. Also, it has been recommended to me to prep the rotors by sanding and re-cleaning their surfaces to get the pads to feel like new again.
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post #10 of 23 (permalink) Old 04-16-2014, 11:08 PM
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Stock brakes should work very well.. I raced on stock pads w/ braided lines at a very heavy braking track and had no issues.

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