The short version of the story is i'm becoming more and more convinced that one of my front brake rotors is warped in some way. I get a detectable oscillation on the front brake at low speed feather braking. high speed braking or hard braking doesn't produce it unless i'm going very slow, but i'm starting to think it's still happening but i just can't feel it due to the speed, because the oscillating "sound" is still audible in the brakes. The oscillation manifests as a perceptible suspension dip at regular intervals proportional to speed, meaning at certain points on the rotor it feels like the brake is grabbing harder. It's not getting worse, it's not getting better, it's just perceptible enough that I know it's definitely there and I can reproduce it at will.
So, What is a boy to do? I'd like to secure a new rotor, but I don't want to buy a brand new one, because they're outrageous. They seem to be really scarce on ebay. is there a good source for second hand rotors that anybody can point me towards? does anybody on the forum have a spare front disc for a 2014 std. model?
Is there anything else definitive that can be causing these symptoms? i've already removed the brake pads, cleaned the pins, cleaned the pads, cleaned the discs thoroughly, all that jazz. I even bled the brakes thinking it was possibly a fluid issue, no change.
Have you checked the runout? In spec?
I don't know of any way to do that.
edit: just consulted a few videos, they all seem to use some kind of single purpose gauge apparatus i have no access to. Looks like that's out unless there's a simpler way to do it.
Did you install new brake pads? That's a relatively cheap way to rule them out.
(12-04-2019, 04:53 AM)KiowaEagle_imp Wrote: [ -> ]Did you install new brake pads? That's a relatively cheap way to rule them out.
Yes actually. It was after the installation of a new tire and brake pads that i noticed the issue. I'm assuming that if the rotor was bent, it was bent during install.
are those rotors thick enough to have them turned ? .. it might not take much..
chuckk ..
(12-04-2019, 04:33 AM)misterprofessionality_imp Wrote: [ -> ]I don't know of any way to do that.
edit: just consulted a few videos, they all seem to use some kind of single purpose gauge apparatus i have no access to. Looks like that's out unless there's a simpler way to do it.
The tool is a dial indicator that you afix to something that doesn’t move and put the indicator on the rotor and spin the wheel around. Then watch and see how much the indicator moves and check that against the spec.
Here is one like I have, although you can pay a lot more, or a lot less.
[url=https://www.amazon.com/Central-Tools-Storm-Run-Out-Indicator/dp/B01MQPLB1G/ref=sr_1_3?crid=3IXBYI4BXJR7M&keywords=rotor+runout+dial+indicator&qid=1575491871&sprefix=Rotor+ru%2Caps%2C151&sr=8-3]https://www.amazon.com/Central-Tools-Sto...151&sr=8-3
BUT, If I was you first I would use a Scotchbrite pad and something aggressive (like maybe acetone) and scrub the rotors real good. It could just be a build up of pad material. A common problem. And you can’t really see it on the rotor. Failing that, the dealer can easily check the runout in a few minutes. I would expect it for free since the problem started after they worked on the bike. YMMV
(12-04-2019, 06:04 AM)Chuckk_imp Wrote: [ -> ]are those rotors thick enough to have them turned ? .. it might not take much..
chuckk ..
Good question Chuck. And I don’t know. The manual just says to measure the thickness with a micrometer and replace if less than the service limit which for the front is 3.5mm (0.14in)
It also says that if the warpage exceeds the service limit to check the wheel bearings for excessive play and if good then replace the disc. So Mr. P, you might want to dismount the front wheel and remount it in the sequence in the manual.
harbor freight has clamp on dial indicators for $33.
MP, assumptions are fine as long as you don't over-rate them, testing various things will point you in the right direction.
From what i read in your explanation there is one friction point on ( one ) of the disks, that does not mean the disk is bent, to test this you can hold a torch behind the brake pad, maybe open the pads up a bit so you can "see the light".
By watching the reflection in the gap and rotating the wheel you are likely to see a change in one place, if the opposite happens on the other side of the disk it is indeed warped and you may have a re-course on the tyre installer.
2nd thought; prise the pads away from the disk, put a sheet of paper in the gap and use the brake lever to close the gap so you can feel the sheet start to lose movement ( like with a feeler gauge ) then repeat the placing at all four pads and see which ones providing the pulsing, you may need some assistance here.
Another simple trick is Kiowa eagle's suggestion, put the old pads in and see if anything changes, here's why;
On my cb900 ( similar system ) i had a buildup of brake pad something, same effect as you describe, pulsing in one place of the wheel, i think this happened when i put the bike away after a wet ride, a little corrosion happened under the pads and because of the change in abrasiveness it picked up some material, i lived with it for some time until the pads needed changing and the problem went away for 90% and improved still more over time, that is all the explanation i can give you and maybe another good suggestion is coming up, no rush, take your time and find out what really happened.
To answer another question asked, a member posted that TRW MST278 is a direct replacement for CB1100 front rotors. I don’t know what they cost.