Strange brake problem

[alexis291]

Something to bear in mind folks when you are deciding to check run out on your disks is that on the K1100 they float. The only sure way to do this will be to remove the disk and mount it on something else, for example a lathe. When I had both of my disks removed I did a simple flatness check by holding them up against each other and measuring the clearance in between them. That showed that they were not warped. I still don't know the exact cause of my problem but it was not disk run out. As I said previously, the only thing I have found so far is a small amount of pitting on one of the disks. The symptoms I had suggested that the friction on the disk was changing as the wheel rotated. I did not get any pulsing at all at the lever.


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[The Mighty Gryphon]

I just finished Spring cleaning on Ilsa and made an observation that may have a bearing on the pulsing issue.  After about 2500 miles since the last wash in early October I did the Spring wash and when I was done rolled her into the garage. 

After putting it on the stand I happened to look at the front discs and saw a spot of road dirt and brake dust that I missed because it was inside the caliper when I did the wash.  Out of curiosity i rubbed the area and found the black stuff to be sticky and didn't want to rub easily off the disc.  Had to go back and get my wheel cleaner to get the spot off.  The spots were on both discs and both sides of each disc.

Hmmm...

[Martin]

I've had to correct run out a couple of times on the brick more on other bikes and race karts. I made up a rig to hold a dial gauge which is attached to the caliper mounting bolt you need to remove both calipers. Once I find the high spot or low spot I gently tap the alloy carrier not the discs, I have a piece of broom handle which I tap with a nylon hammer. You need to do this gently and this can take a bit of time but it has cured pulsing.
Regards Martin.

[alexis291]

Gryph - noteworthy but I scrubbed and rubbed my disks for hours. And my problem started after riding for 3-4 hrs and had not been there when I set off.
Martin - interesting but this does not address the issue that the disks float (on the 1100RS at least) so checking runout accurately on the bike is not possible.


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[Laitch]

Gryph - noteworthy but I scrubbed and rubbed my disks for hours. And my problem started after riding for 3-4 hrs and had not been there when I set off.
Martin - interesting but this does not address the issue that the disks float (on the 1100RS at least) so checking runout accurately on the bike is not possible.

Consider that some or each of your brake pistons are sticking intermittently.

[Martin]

It only works with the solid discs, my next front discs that are waiting in the wings are fully floating. So I won't be able to correct run out.  :dunno

[Motorhobo]

When installing the rotors (on any vehicle), ensure the mating surfaces are void of dirt, rust, grease... Basically, make sure the surfaces are clean. That's the hub, the rotor, the wheel. Even the most precisely torqued installations will be off if the areas are not clean and flush. Also, follow the torque pattern, but not all at once; rather,  increase torque values two to three times, i.e. Pattern to initial contact and set, then 25% of rated torque, then 75%, and then final torque.


Somewhere on this thread, or somewhere else, someone mentioned coming to full/abrupt stops, and then keeping the pads held in the original point of stop. It basically ruins the even coat of break-in material (burnish) of the pad on the rotor. If this occurs, it's best to re-break-in your pads. Best practice is coasting just a hair before coming to complete stops. Make sense?


There's plenty of documentation out there indicating why this is a best-practice for pad/rotor braking... Here's a simple means of burnishing. The best part is that if you've not yet done this, you can always go out and get it done. Better late than never.


http://www.wagnerbrake.com/technical/technical-tips/break-in.html

Thought I'd follow up on this -- I installed new pads and retorqued the disks based on jay1622's advice above -- pulsing all gone, smooth braking all around.




Thanks, jay1622!