A thumbs-up for DaveNZ (brakes) - 2018 KTM 790 Duke Forum
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post #1 of 3 (permalink) Old 10-05-2019, 11:57 PM Thread Starter
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A thumbs-up for DaveNZ (brakes)

I’ve read several posts about warped disks and/or “pulsing of the brakes” and mentally filed it away in case it ever applied to my bike.

A few weeks ago, I noticed that whilst slowing from low speeds (e.g, approaching a T junction), my front brake seemed to slightly grab, release and grab again under light pressure on the lever. Although spinning the front wheel didn’t reveal any rotor warping or runout to the naked eye, it was still a bit worrying.

However, I tend to be very light on brakes and my cornering style is a combination of observing the vanishing point and using throttle and gearbox accordingly. Looking at the front rotor faces, they appeared glazed and I wondered whether my light use of brakes had contributed to this. I mentioned this in a recent post and DaveNZ recounted past experience on his Multistrada and how he addressed the problem.

Yesterday, I followed Dave’s advice and used 400 wet and dry paper (wet) on a block to remove the glaze on both sides of each rotor then washed them thoroughly. Also removed the pads and lightly sanded them in a figure of 8 pattern on a flat plate, then sprayed them with brake cleaner.

Went out today to a straight(ish) side road and repeatedly did high speed stops to build up rotor temperature. Back to the village and no more low speed judder! Dave, you’re a star mate – thanks so much for the tip.

If anyone else suffers from these symptoms, it might just be worth trying Dave’s remedy before worrying about warped rotors!

Photo on the left is the rotor after cutting the glaze but before riding. Photo on the right shows nice even marking after a whole series of stops from high speed.
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post #2 of 3 (permalink) Old 10-06-2019, 12:47 AM
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Glad it worked Geoff, and hope the pulsing doesn't return, but in all likely hood it may return. Its a symptom of medium quality disc's, they get whats called hot spots, (machined with in .004 or something, high quality could be .001) and with in the metal hot spots there is a change in I'm not sure the term, (metallurgy??) and brake pad material builds up different in those hot spots. Thats why when running in bikes and brakes from new its essential that brakes are bedded in hard to get a consistent even heat through the entire disc early on, and not hot spots.
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post #3 of 3 (permalink) Old 10-06-2019, 01:43 AM Thread Starter
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This is the first time I've come across this issue on any of my bikes but as an engineer, your comments sound quite plausible. I'd imagine that the composition of the pads also have a bearing. I'm still on the OEM ones and when I switch to EBC HH in due course, it will be interesting to see what happens. Big fan of HH's on previous bikes.

If I have to repeat the exercise, it's no big deal. It took about 2 hours to complete the job and I can substantially reduce that now that I know what I'm doing!

Thanks again Dave!
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