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Discussion Starter · #1 ·
Hey guys, so after a near catastrophic incident during my last race round at PIR I am going over the brakes with a fine tooth comb. Here is a video of the excessive drag and squeal I am experiencing.
I always have fresh, bled fluid..i clean caliper pistons and rotors with soapy water and toothbrush 2-3 times a season, and when I reinstall the front wheel I will keep the caliper bolts loose, spin the wheel, apply the brakes to center up the calipers, and then tighten caliper bolts.
i always try to keep an eye on the drag, and do everything I can to keep the front wheel spinning as free as possible. The squeal didn't come until this season when I made the mistake of switching out my Vesrah RJL'S that I had used the past 2 seasons. Renthal has been a good sponsor to me so I thought I would give their sintered RC-1 pads a chance. They have had good stopping power all season, but I would get that eerie squeal while rolling my bike around.
I am running a Brembo RCS 19 M/C, EBC Rotors, Core Moto lines(6yrs old), Renthal RC-1 pads, Kurveygirl titanium banjo bolts, w/motul rbf 600 fluid.
I do have 31k miles on the calipers without a rebuild, but they are not leaking and I have kept them clean. Any suggestions are appreciated, and I'll let you know what I come up with and how I rebuild them. Thanks!

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Discussion Starter · #4 ·
I'd bet money on a warped rotor.....
I did forget to mention that I experienced some unsettling feedback in the lever during the last race. Almost like the lever was pushing back against my finger. I could only use the lightest of pressure, otherwise they would almost lock up on me.
I did set up a mag base and dial indicator up against the rotor and spun the wheel slowly. They were between .008-.010" total run out. I don't know if that would be enough to be the cause. I did mic the thickness of both rotors and one was .0025" thinner. And yes, I still do have the pad springs installed. On a side note, I did have trouble with that spring and the Renthal pads lining up properly. The pad wanted to naturally sit above the spring, not against it.

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The sound of it hitting/scraping at one specific point on the rotation is a telling indicator of an out of plane condition. The pads are only meant to move in a few ten thousandths of and inch to engage.... the rotor is coming to meet it.
 

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Do you clean the rivets between the rotors, and their carriers? Ensure they can move? That's where the rotors' expansion and contraction are accounted for.... If some of them are binding up, the rotor will have to go sideways, and may not be able to come back to 'flat' when it cools...
 

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Discussion Starter · #7 ·
Do you clean the rivets between the rotors, and their carriers? Ensure they can move? That's where the rotors' expansion and contraction are accounted for.... If some of them are binding up, the rotor will have to go sideways, and may not be able to come back to 'flat' when it cools...
I do, with a toothbrush and soapy water. I haven't taken it the step further and secured a nut and bolt through them to move them around however. I bought them brand new before the 2017 season.
To rule out the rotors I am gonna run a set of oem that I picked up that are much straighter and just as thick. I am also going back to the Vesrah RJL's.
RJ, have you rebuilt your calipers within your 60k miles? I didn't know if I should get in there since I have them removed at the moment. I figured I'd just remove the pads, and try to squeeze the pistons out a bit to clean them even better. I'm having trouble getting them all to pop out as much as I'd like though.

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I'm sure at this point Rivers thinks I'm an idiot, LOL. No, I haven't rebuilt my calipers. It's obviously a good idea; it hasn't bit me in the arse yet and I don't place all that serious a demand on my brakes just riding on the street.

A track bike which sees multiple heavy heat cycles each time it's used, and then sits for a week or two before getting ridden just as hard I would probably pay considerably more attention -- especially if I am getting indications of something amiss.

The extra time doing preventative maintenance is far better than having to mend your body, and then do it anyway.

v/r,
 

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Take one caliper off and see if it still makes the noise an vice versa. Also when you take the pads out to inspect the calipers, make sure all the pistons move when you apply pressure with the lever. If one of them isn't moving, take a piston removal tool and try to spin the piston in the caliper. If one of them is really stubborn, just rebuild them. Your bike and your lap times will thank you.
 

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Discussion Starter · #10 ·
Take one caliper off and see if it still makes the noise an vice versa. Also when you take the pads out to inspect the calipers, make sure all the pistons move when you apply pressure with the lever. If one of them isn't moving, take a piston removal tool and try to spin the piston in the caliper. If one of them is really stubborn, just rebuild them. Your bike and your lap times will thank you.
That's a good idea that I wish I thought of before I removed the pads. I tried pumping the pistons out a bit with the pads removed, and only 1 of the 8 was moving freely! I may have introduced air to the system before hand by cracking the banjo bolts loose a bit, but I would have thought there was still enough pressure to move some of the others out. They were pulsing, but they should of been popping out some.

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Did you notice any uneven wear on the brake pads? Measure the leading edge and the opposite side of each of them. Hopefully you marked which one came out of where. Did you notice any pulsing in the lever during the incident you had? I had a similar issue where I could only get on the brakes a little bit before it would damn near shake my arms out of their sockets. A replacement of one of the rotors fixed the issue. It's starting to sound like maybe excessive brake drag caused a rotor to overheat and warp which is what led to your cheek clenching moment? Are those aftermarket wheels?

Also just for fun I checked the manual to see what the limit was for runout. It looks like 6 thousandths is the standard measurement but it also says the service limit is .01. If i remember correctly the one that was warped on mine was about 25 or 26 thou which made the brakes feel like a jackhammer.
 

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Discussion Starter · #12 ·
Did you notice any uneven wear on the brake pads? Measure the leading edge and the opposite side of each of them. Hopefully you marked which one came out of where. Did you notice any pulsing in the lever during the incident you had? I had a similar issue where I could only get on the brakes a little bit before it would damn near shake my arms out of their sockets. A replacement of one of the rotors fixed the issue. It's starting to sound like maybe excessive brake drag caused a rotor to overheat and warp which is what led to your cheek clenching moment? Also are those aftermarket wheels?
Haha yeah I puckered so bad that it sucked the bike back down and kept me from going over the bars lol. I didn't notice any unusual wear of the pads, but I thought it was weird that one rotor was a decent amount thinner. Of course that could've been going on he past couple of seasons though. I am assuming since I have the calipers off I should go ahead and order the seals to rebuild them. They're like $80 just for seals.
It did have me thinking of other culprits though. What do y'all know about the differences in banjo bolts? I know Kawi did their research, I am sure core moto did some as well, but Idk about the aftermarket titanium ones I have been using. Look at all the different size orifices of each. Oem on the right, Core Moto on the left. I also took a bunch of measurements to make sure that I use the correct sized crush washers to center the banjo bolt properly. Do you think the flow rate of the banjos could affect caliper engage/retract? Or am I thinking too hard?


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Time for full floating rotors. Braketech or Brembo ? ;). I wouldn't worry about the banjo bolt or brake lines unless they're leaking from somewhere or damaged. Check the rotors for warpage. Brakecrafters has good caliper rebuild kits available.
 

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I'm not entirely sure but I would think that the orifice size on the banjo would make a slight difference to your initial bite on the lever. I wouldn't think that it would cause an issue like you are having. Now that I'm thinking a little more, your EBC rotors might have different specs than OEM for acceptable runout. Maybe call them to see what exactly the limit is. You also mentioned that one of the rotors was thinner than the other, check the part numbers to see if they are the same.
 

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I hope the OP has better luck with the rebuild of the stock calipers than I did. I found that the stock calipers, even after a rebuild, are not the greatest. The pistons still protrude unevenly and cause uneven wear on organic pads (but not sintered, for some reason). I ended up switching to difference calipers ...
 

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Discussion Starter · #16 · (Edited)
JD, if money wasn't an issue right now they would be some new rotors lol
I'm not entirely sure but I would think that the orifice size on the banjo would make a slight difference to your initial bite on the lever. I wouldn't think that it would cause an issue like you are having. Now that I'm thinking a little more, your EBC rotors might have different specs than OEM for acceptable runout. Maybe call them to see what exactly the limit is. You also mentioned that one of the rotors was thinner than the other, check the part numbers to see if they are the same.
I guess the hole size on the banjo would really only affect brake pressure and not retract? To be clear the brake system has been solid and consistent braking power all year up to last round. Which is why I ignored the horrendous squeal I guess. The drag wasn't always that bad either, not great though, even with the Vesrah pads the past couple of seasons.

So it's looking like I'll be replacing the lines as well now. Since I basically wanted to go through both front and rear systems thoroughly, I removed the brake lines. I did the rear first and when I did I noticed some gunk on the banjo. It was the black paint/coating that was peeling away, and the only place for it to go is into the line! The fronts had the same happening, but not nearly as bad. I'll be contacting core moto tomorrow to see if that is under warranty.

Zx6rguiy, to your earlier question, yes they are aftermarket wheels. Carrozzeria V-Track by Core Moto. I got them forum member @Johnmark101. They are mint!


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If you're really that strapped for $$$ I have no problem donating my stock spare rotors to you. Just PM me. I mean as a racer.
 

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Discussion Starter · #18 · (Edited)
If you're really that strapped for $$$ I have no problem donating my stock spare rotors to you. Just PM me. I mean as a racer.
That's an awesome gesture JD and I appreciate that! I'll be ok financially..after the season ends . I just happened to get hit with a truck repair, then my tire warmer went out, I ended up paying $175 for lightly used rotors from a fellow racer's street bike. I also have to get some Vesrah pads, and most likely brake lines now. So the extra $300-$400 for aftermarket rotors was a stretch. Mostly because I'm liking my 3 and 4 day weekends from work too much instead of working OT like I did in the off season .

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I have exactly the same on my ZX track bike, I've replaced everything and never really made much progress. The only thing i never change were the discs to fully floating as this should help.
 

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Discussion Starter · #20 ·
Yeah I am a little leery about rebuilding the calipers. I can only imagine the cement Kawi used to bolt the halves together. They are not leaking, but I am concerned if any of the chipped powder coating from the banjos got into the calipers. What calipers are you using now?

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I have exactly the same on my ZX track bike, I've replaced everything and never really made much progress. The only thing i never change were the discs to fully floating as this should help.
I don't really know how much I should expect it to spin, but this isn't good at all. I'm usually happy if it spins about twice around and comes to a gradual stop from whatever drag there is.

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