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possible bent rotor, new rotor sources?
#21
(12-08-2019, 06:58 AM)Chuckk_imp Wrote: gotcha.. did you find out the cost of a rotor

about 110 with shipping and tax if i buy the TRW variety.
(12-08-2019, 07:46 AM)max_imp Wrote: MP that is a very detailed description of what you have done and found out, to add a bit more weight to the scale;
If the rotor is bent the opposite effect happens on the other side of the disk, the paper should free up some in the same place ( that you hopefully marked ), if it does not then it's not likely warped and repairable somehow.
( on my cb900 i could not tell the friction spots no matter how hard i looked at the disks and cleaned them, it just went away with new pads, lucky me ).

I think you found out more than the average service shop would, at least you've found the spot and direction of what pulses the brake, you also tried the old pads and found no difference, that's important and overall have established that this pulsing started after the tyre was replaced, also good information.

Would be a bit hesitant to sand the surfaces, you could induce some
'random"abrasiveness that would accumulate more friction in places and make things more complicated, i can't prove this but that is just my hunch.

As for the calipers; they are stationary and thus unable to "choose" a spot in the wheel to grip harder than other spots, what may alleviate things a bit is to check the right hand side pistons for free movement and free of dust and grime, all be it very small amounts if the pistons are not free to move that may play a part, like the rear caliper that's engineered to "float" sideways with brake pad wear and "self align" to the disk, alternatetively loosen the two bolts on the fork leg and give the caliper some wiggle room, don't forget to tighten them back up.

When you lift the front wheel does the disk drag in one place or are the pistons completely free, retracted and make no noise?

i cant say if the paper frees up on the other side, only that it doesn't catch.

when the wheel is free off the ground and spinning the pads have aways "dragged" in that i can hear them sound of the disc sliding through them. this is true with both new and old pads, once the calipers are pressurized. The is not new, though. it's always been the case. there's no pressure and the brake is not impeding the free motion of the wheel. This is normal, as every disc brake motorcycle i've ever had makes that sound when spinning freely.

However, i do not hear the high spot when the wheel is just rotating freely in that way. the only time i can hear the "shuck shuck shuck shuck" oscillation sound is when i'm actually applying the brake at low speeds.
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#22
Mark,
Pads, causing brake pulsation = never had/never heard of, IMHO don't think so...

If you do not have a profesional dial gauge (you should have itTongue , due to number of bikes you do/alter/fix..) , you can:
1* make sure front wheel is free off the ground. For smooth f/wheel movement, make sure pads are not touching rotors. Don't have to take them out, just pry away from rotors, while NOT using rotors as a fulcrum, too skinny!!
2* take an unrolled paper clip or solid wire and place it between your thumb and front fork, while p/clip edge is gently touching front rotor. Instead of your tumb, you can tape it.
3* slowly and evenly spin front wheel while observing clip's sideway or/and directional movement. It will indicate run out, and may give you an idea if significant or any. Test two front discs.
This will give you better idea what's going on, but I think your rotors got bent during tire replacement.
I assume, front rotors were not removed while re-re tires and front wheel has axial/radial run out within specs =0.08 in/2.0 mm

Maximum front rotor run out = 0.008 in/0.20 mm

MAX idea with binding method is good as well...+ while front wheel off the ground, gently apply front brake lever until pads have contact with rotors, then evenly/smoothly spin the front wheel... any intermittent drag/tight spot, may indicate run out/bent rotor(s)
Diagnose first before $pending money
Good luckThumbs Up
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#23
It wasn't really a question in my mind anymore, but to button up this thread with some hard facts, yes it was definitely a bent brake disc. the bend was nigh imperceptible, but it was completely cured the moment i put a new disc on. i got lucky and scored an OEM one off ebay for 25 bucks.

the old disc fit perfectly against the new disc when they were compared, with no gaps and no perceptible variance. if i hadn't marked the new one i might not have been able to tell them apart, and yet the bend was there, just enough to make my front brakes herk and jerk.

I don't know what to do with the old disc. perhaps just trash it?
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#24
Problem solved, glad to hear
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#25
That's great Mr. P. Recycle the old disc, if possible. (e.g. a metal scrapper won't let it make it to the landfill).

- - -

PB: Do I sense RLETs in your near future? (new avatar)
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#26
I noticed that too...
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#27
.......near future, possibile????

"stronger than most with the Force, wise and powerful, trained Jedi for over 800 years, unlocking the path to immortality"

Padawan no longer he is....
SmileHello
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#28
you will need "the force" on your side, to get those RLET's installed ..ROFL
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#29
...or I'li come with my bike to Ventura and watch the installation with exitment Tongue
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#30
yes Peter.. then after we can ride my hwy 33 !! ..
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