Track Bike Vibrating Brakes Issue

[A.Thoeny]

Hey guys,

I need some help troubleshooting an issue with my track bike. I bought it back in October of 2017, and rode it for the first time this past weekend at a Z2 event.

Before riding it this past weekend, I changed the oil/filter, air filter, rebuilt calipers, flushed coolant, changed fork oil/seals, changed fuel filter and of course fresh rubber. The only thing I did not do that I wanted to was refresh the rear shock, but that'll be done sometime in the future.

Anyways, at the track on Saturday I was getting vibration/chattering on the front brakes after ~40% braking force, so I was timid on the brakes for most of the day. Still had an absolute blast, but was limited by the braking issue. All bolts on the bike were done to spec using a torque wrench, and bolts on the caliper were done using blue thread lock. The calipers have vesrah pads in them.

Here's a link to the classifieds sale post:
http://bayarearidersforum.com/forums/showthread.php?t=519545&highlight=750+track

I was planning to check the rotor straightness using a dial indicator with the bike on a front & rear stand, but any help and advice would be greatly appreciated.

I ride mid/upper B pack.

Thanks!
Alexis

 

[DannoXYZ]

Were you pitted near start/finish?

Check:

- check pads & disc for oil/grease. Just tiny thumbprint can cause shuddering

- use external micrometer and measure thickness of disc at random positions all around

- wheel-bearings and play

- steering-stem bearing preload

- fork-damping settings? too much compression/preload & not enough rebound can cause bouncing

- do you have slipper-clutch?

 

[Junkie]

Are the pads new? If so, what was there before?

 

[Junkie]

Presuming you have floating rotors, checking runout is pointless.

 

[bobl]

If the pads are new, sanding the rotors, and resurfacing the pads may help. Pads deposit materiel on the rotors, and changing pads to a different brand often requires sanding down the rotors to clean them of previous pad materiel.

 

[ST Guy]

As long as the lever is not pulsating, then it's a dirty rotor or a rotor with unevenly deported pad material. Essentially there are areas on the rotor surface that have, for one reason or another, different coefficients of friction.

Try some brake cleaner first and thoroughly clean both sides of the rotors. That may be enough to fix it. If it doesn't, you'll need a more aggressive means of getting down to fresh metal and then you can lay down a new layer of pad material on the rotors.

FYI, if you changed pads but the pads are the same brand and model as before, you may be able to get away with just the cleaning and then a new bedding of the brakes. But again, if that doesn't work, you'll need to really clean the rotors.

 

[sckego]

I had a really nasty front end shudder under braking on my FZ1. Never noticed it on the street, but at the track it was really bad. Tried a few different options, eventually Fastline ended up replacing the rotors for me, that fixed it.

 

[ST Guy]

After you clean with brake cleaner, you can also try cleaning the rotors with acetone and then with isopropyl alcohol as a final step. Don't get the acetone on any painted surfaces. And use clean rags.

 

[OaklandF4i]

You are on the right track. In addition to what Danno has suggested, also thoroughly clean each of your floating rotor's buttons assuming you have floating rotors. I chased a similar vibration on my CBR track bike years ago with brand new rotors, pads, and rebuilt calipers. Would only happen after brakes had fully warmed up and under hard breaking at the track. Its was a couple of the buttons that werent as "free" as the others. Once rectified..... no more brake shudder. You experience may vary.

 

[A.Thoeny]

Were you pitted near start/finish?

Check:

- check pads & disc for oil/grease. Just tiny thumbprint can cause shuddering

- use external micrometer and measure thickness of disc at random positions all around

- wheel-bearings and play

- steering-stem bearing preload

- fork-damping settings? too much compression/preload & not enough rebound can cause bouncing

- do you have slipper-clutch?

I was pitted under the second canopy, closer to the first canopy. Fork settings were set by JPH on Saturday morning before I went out. No, I dont have a slipper clutch. I cleaned the rotors with brake cleaner before going out, so I don't think there is any grease/oil, etc on them. How would I check for wheel bearing play and steering stem preload?

I also checked runout, total displacement was within 5 thousandths on both rotors, so +- 2.5 thou, which I assume is in spec. Using calipers, the thickness variation of individual calipers was less than 1 thou anywhere on a rotor, and were virtually the same thickness between the two rotors.

 

[A.Thoeny]

Are the pads new? If so, what was there before?

Previous owner said pads were pretty new, and I think they are based on remaining pad thickness. I am not sure what was on beforehand.

You are on the right track. In addition to what Danno has suggested, also thoroughly clean each of your floating rotor's buttons assuming you have floating rotors. I chased a similar vibration on my CBR track bike years ago with brand new rotors, pads, and rebuilt calipers. Would only happen after brakes had fully warmed up and under hard breaking at the track. Its was a couple of the buttons that werent as "free" as the others. Once rectified..... no more brake shudder. You experience may vary.

How would you recommend cleaning the rotor floating buttons?

 

[nakedape]

Previous owner said pads were pretty new, and I think they are based on remaining pad thickness. I am not sure what was on beforehand.



How would you recommend cleaning the rotor floating buttons?

Bolt through them and spin with wrench while shooting brake clean at them. Sadly, you may have what I had going on, which was microscopic imperfections after many miles which run out doesn’t reveal.

Like the other FZ owner here, I had to replace rotors to fix. Sucks, but that’s a used bike for you. Try the other options in order first, then give up. Buy quality rotors and focus on the next failure.