brake fade - Page 4 - Kawasaki ZX-10R.net
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post #31 of 112 Old 02-16-2007, 08:59 AM
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Also, by changing the pads , you would have had to pump the lever again to get line pressure backand push the pistons out, on the first set if you pumped the lever did you get line pressure back at all ?
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post #32 of 112 Old 02-16-2007, 09:09 AM
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One thing I did notice when I first bled my brakes (after approx 100 miles) the fluid in the caliper was contaminated and it looked like brake seal material , it may have been a reaction with assembly lube or the lube itself,I dont know, but since that day I havent had it occur again.

Also , you must check the torque settings on two piece calipers to avoid air leakage around the fluid passage and O ring , new bolts will always stretch a little.
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post #33 of 112 Old 02-16-2007, 11:36 AM Thread Starter
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After reading all the posts, I don't think I had brake fade. It is just that the lever came back a bit more than it did when cold. Now that everthing is cooled down, it feels like normal. I must have air in there somewhere. My fluid is new RBF600, and I used a mityvac to bleed before the trackday. I don't have stock lines, so no cross over line, just 2 straight lines. My pads are a bit worn now too. I will try a combination of mityvac and brake lever squeeze to bleed next time. Still think the stock MC is crap.

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post #34 of 112 Old 02-16-2007, 11:45 AM
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When you bleed the brakes ,look at the position of the handlebars on full lock one way the master cylinder is pointing downhill this can leave a small air bubble at the back of the cylinder.
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post #35 of 112 Old 02-16-2007, 11:47 AM
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My bike has stood for a month, I will be bleeding the brakes soon, I can almost guarantee there will be air at the top of the lines.
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post #36 of 112 Old 02-16-2007, 12:49 PM
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Hrmmm... needs like I need to take better measurements and do this in a more controlled environement to get to the bottom of those questions. I don't think I 'beld' any air by pushing the pistons back... and I found it strange that when I put the half worn pads back on that the problem immediatly came back. However, the old pads were steet pads; god only knows what possible contaminates are in them. The new pads were just that... right out of the box.... and everything worked perfectly with them.

The big question for me is: why in a hydraulic system like this is the amount of pad changing where the lever starts to bite at race track temperatures? The new pads bite within a 1/4" of the lever being pulled (at track temp), whereas the old pads will not bite until the lever has been pulled almost halfway back. No amount of 'pumping' the lever would bring the bite closer either (rules out the rotors pushing the pads out at speed... I did think of that too)If it's air somewhere, why is it only effecting the system when the pistons are further out? And why only when it's hot.

Pretty strange... but thanks for the feedback... I'd like to get to the bottom of this someday ;)

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post #37 of 112 Old 02-16-2007, 12:49 PM
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Quote:
Originally Posted by 05Ti10
After reading all the posts, I don't think I had brake fade. It is just that the lever came back a bit more than it did when cold. Now that everthing is cooled down, it feels like normal. I must have air in there somewhere. My fluid is new RBF600, and I used a mityvac to bleed before the trackday. I don't have stock lines, so no cross over line, just 2 straight lines. My pads are a bit worn now too. I will try a combination of mityvac and brake lever squeeze to bleed next time. Still think the stock MC is crap.
Yeah, calling it "brake fade" might have confused some people. Like I said before, myself and others have experienced the same thing you did when taking the 10 to the track. Braking power is still there. It's just that you have to squeeze the lever more and more to get the same effect. And I'm telling you it doesn't matter how much or how well you bleed the brakes. After some hard laps the lever will come to the bar. You are correct about the oem m/c being crap. If you want to fix it, go here and talk to them about your issue. www.kyleusa.com If you or anyone else doesn't know who dan kyle is he was the crew chief/engine builder for two brothers racing and erion racing back when they were kicking everyones butt with 900RRs.
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post #38 of 112 Old 02-16-2007, 01:15 PM
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Quote:
Originally Posted by SpazOnaZX
The big question for me is: why in a hydraulic system like this is the amount of pad changing where the lever starts to bite at race track temperatures? The new pads bite within a 1/4" of the lever being pulled (at track temp), whereas the old pads will not bite until the lever has been pulled almost halfway back. No amount of 'pumping' the lever would bring the bite closer either (rules out the rotors pushing the pads out at speed... I did think of that too)If it's air somewhere, why is it only effecting the system when the pistons are further out? And why only when it's hot.

Pretty strange... but thanks for the feedback... I'd like to get to the bottom of this someday ;)

Air expands when it gets hot , the bubble gets bigger, sometimes the bubble will divide into smaller bubbles or even ends up as froth.

As for the bite feeling being different this would depend on the pad and rotor combination, different pads have different cooefficients of friction and these too vary with operating temperatures so greater pressure is required for a pad with a lower coeeficient.

Another thing to consider is more heat transfer through thinner pads , the thinner they get the hotter they get under the same conditions, the hotter they get the the more they wear ,then they get hotter !!

We spend a considerable amount of time calculating brake wear for long races i.e 24 hours of Daytona , 50% of wear thickness is not 50% of the time left to go before they have worn out, it becomes exponential, and calculating the time to change the pads during a race is a nightmare.

But for a track day I would use new pads for better consistancy anyway.

As for the spongy feeling when the pistons are further out , it could be vacuum related.
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post #39 of 112 Old 02-16-2007, 05:50 PM Thread Starter
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Quote:
Originally Posted by phastone
Yeah, calling it "brake fade" might have confused some people. Like I said before, myself and others have experienced the same thing you did when taking the 10 to the track. Braking power is still there. It's just that you have to squeeze the lever more and more to get the same effect. And I'm telling you it doesn't matter how much or how well you bleed the brakes. After some hard laps the lever will come to the bar. You are correct about the oem m/c being crap. If you want to fix it, go here and talk to them about your issue. www.kyleusa.com If you or anyone else doesn't know who dan kyle is he was the crew chief/engine builder for two brothers racing and erion racing back when they were kicking everyones butt with 900RRs.
I know Dan Kyle Racing, bought my Sato pipe from him at Laguna 05. They know their stuff for sure. Looks like a brembo 19X18 is the one. Thanks.

Steve
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post #40 of 112 Old 02-17-2007, 12:16 PM
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Quote:
Originally Posted by FAF
Air expands when it gets hot , the bubble gets bigger, sometimes the bubble will divide into smaller bubbles or even ends up as froth.

As for the bite feeling being different this would depend on the pad and rotor combination, different pads have different cooefficients of friction and these too vary with operating temperatures so greater pressure is required for a pad with a lower coeeficient.

Another thing to consider is more heat transfer through thinner pads , the thinner they get the hotter they get under the same conditions, the hotter they get the the more they wear ,then they get hotter !!

We spend a considerable amount of time calculating brake wear for long races i.e 24 hours of Daytona , 50% of wear thickness is not 50% of the time left to go before they have worn out, it becomes exponential, and calculating the time to change the pads during a race is a nightmare.

But for a track day I would use new pads for better consistancy anyway.

As for the spongy feeling when the pistons are further out , it could be vacuum related.

Ok... some good stuff there... but I have a few more comments/questions (I love this shit... I'm really in the wrong field)

I realize that air expands when it gets warm, but so does fluid. If anything the air in question trapped would be under more pressure as temerature increases... as the temerature of the fluid around it also increase... the air will give in that contest before the fluid does. I've seen it in our old school machinists' levels at the shop: on hotter days, the thing is more accurate, as the air bubble in the level will get smaller as the fluid around it expands. Air will always give before the fluid, right? But, I suppose if the air is expanding while the lever is not being pressed, it would push the fluid back through the master in the resevior.... and I could see that causing similar symptoms. Do you think the air could possibly develop enough pressure to do that in this system?

I never meant to say that the bite felt different... just that it bites at a different point in the lever travel. Even with different pads, the bite felt remarkably similar. However, I didn't think about exponential brake wear/heat like that.... it's a helluva good point (thank you!). I could fathom that the pads are getting SO hot that they are giving that -impression- of not having any bite until you apply enough pressure to overcome it.... does that sound plausible?

Interesting... thanks for the feedback.

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Last edited by SpazOnaZX; 02-17-2007 at 12:19 PM.
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