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Throbbing (warped?) rotors.

J

JoeFaz

Tuned and Synch'ed
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I have recently noticed a throbbing, pulsating sensation on my from brakes ('09 Norge, ABS, 4400 miles).
I have read through some of the previous posts on "spinning rivets" but I'm lost on thaty as I have no idea what that is or how/why to do it. My bike is still under warranty so I don't really want to mess with a "shade tree fix". Just wondering if anyone has had actual warped rotors and if so, did Guzzi replace them? I had a new '99 Bassa with the same problem, and they replaced them under warranty way back when.
Thanks.
 
Joe, the "warped" rotors were the Braking disks fitted to some sports in 07 08. If you have abs? They will be different disks. To isolate the problem, take your bike to someone who can measure runout on the disks. If they are faulty, Todd has some good replacements in his store (see store tab above). The original problem with the wavey disks was the pad material buildup on the rotors causedby the brake rotor bobbins were a tad too tight, hence the "spinning of the rivets/bobbins" to free them up.
 
They do appear to be either warped or have developed very small thin spots, even 0.02mm variation in thickness can cause problems,. The correct method is to check the thickness with a micrometer all round the disc and measure the run out with a dial test indicator clamped to the fork leg.
Guzzi have replaced discs under warranty so you should not have a problem if they are proved to be defective.
EBC HH pads help prevent future problems.
http://www.blackshadow-uk.co.uk/Fitting.html
 
My 2008 1200Sport with wave rotors had bad pulsing from the front. I replaced the pads with EBC HH pads, sanded the rotors with garnet 80 grit (don't use aluminum oxide), and cleaned and rotated the buttons with brake cleaner until they moved freely. Several aggressive stops to bed in the new HH pads and the pulsing was greatly reduced - left rotor was floating cleanly with no warping, right rotor was floating freely but is warped, easily detected rotating the wheel through the caliper, no runout dial needed.

No warranty so I'll live with the gentle pulse from the right rotor (I can only feel it when coming to a complete stop, no pulsing when braking normally or aggressively). When / if I need new rotors, I'll upgrade then.

If you've got pulsing from non-wave rotors, I suggest several aggressive stops. 60mph to 5mph at 90% braking effort, not activating the ABS (which would be 100%). Accelerate normally to 60mph to let the brakes cool a little then do it again. This will move the rotors around and free up the buttons and scrub off any pad build up. Brake hard whenever you ride to keep everything smooth!

Tom
 
Just a thought. I had severe throbbing from the front brakes on my '08 1200 Breva when coming to a stop or going slowly down a steep hill. Turned out to be badly glazed brake pads. Scuffing them up on rough concrete then a good clean completely solved the problem.
 
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