Symptoms of a failing brake rotor & is rotor bobbins maintenance for real?

[Pursuvant]

I've had a front left brake rotor failure - the carrier appears mis-shapened by the forces at work. It's the original OEM rotors, used 4 seasons & 82K miles, no track days.

Recognizing symptoms: all this riding season I have rare events, some kind of "movement" of stressed hard parts sometimes with sounds when braking. Attention is drawn to the front end because it's felt in the bars. I run thru the possibilities - calipers/pads, steering head, forks, and wheel bearings. Inspection looks normal, forks are moving smoothly, steering head seems secure.

I recently had major service - at 76K miles, to get this bike ready for "the second half of it's life". Forks & Ohlins cartridge service, fluids, seals, steering stem adjusted, all new wheel bearings, check/grease suspension linkages & swingarm needle bearings repacked, ++.

I expected this would take care of the mystery "movement". Instead I had the real problem make itself known:

Limped home at 35mph. Ordered new OEM rotors because $92 each, and brake parts and seals I don't already have.

Question - OEM rotors are semi-floating, should the "buttons/bobbins" be "cleaned"? Should I be spraying the bobbins with brake cleaner & blow them out with the compressor a couple times a year?

FYI the web has lots of cleaning recommends for full-floating rotors, spinning the bobbins with a drill. That seems like a bad idea to my senses, and not for semi-floating rotors.

[sweetscience]

Nah, don't waste your time.  No amount of cleaning will extend the life of those rotors.  Rotor design could extend the life however.  Aftermarket rotors utilize 10 bobbins, have thicker rotors and carriers.  Usually though, aftermarket have aluminum carriers for weight savings and performance. So that may hinder longevity.  These OEM are all steel rotor and carrier.  Anyways, give yourself a pat on the back for taking them this far. 

PS, if you don't mind, could please tell the weight of a brand new OEM rotor when you get them? 

     

[Claude]

I never believed in the maintenance needed on semi-floaters bobbins. I never had full floaters on any of my bikes but I believe to think that they would need some maintenance. But on semi-floaters I think it could maybe make someone feel better but nothing more.

[Pursuvant]

16 hours ago, sweetscience said:

...These OEM are all steel rotor and carrier...

PS, if you don't mind, could please tell the weight of a brand new OEM rotor when you get them? 

     

2.6 lbs on a not especially accurate digital scale, without bolts.

I checked a couple bobbins on each new rotor, trying to move them with my hands - they don't. You can see the "wavey" washer under the bobbins retainer that opens up space for floating.

For reference the rotors & new bolts OEM part numbers below:

1WS-2581T-01-00 DISK BRAKE ASSY (Yamaha) $93.67

90109-06254-00 BOLT (Yamaha) $5.75

You will need new bolts, 5 on each rotor. And I put on fresh EBC double H pads, knowing I'll be breaking in the new rotors (and pads) and that process distributes the pad material evenly around the disk.

At season end the calipers will get rebuilt, because they have about 70K miles since the new seal kits I put in after powder coating them.

[shinyribs]

On 9/19/2023 at 9:47 PM, Pursuvant said:

I've had a front left brake rotor failure - the carrier appears mis-shapened by the forces at work. It's the original OEM rotors, used 4 seasons & 82K miles, no track days.

Recognizing symptoms: all this riding season I have rare events, some kind of "movement" of stressed hard parts sometimes with sounds when braking. Attention is drawn to the front end because it's felt in the bars. I run thru the possibilities - calipers/pads, steering head, forks, and wheel bearings. Inspection looks normal, forks are moving smoothly, steering head seems secure.

I recently had major service - at 76K miles, to get this bike ready for "the second half of it's life". Forks & Ohlins cartridge service, fluids, seals, steering stem adjusted, all new wheel bearings, check/grease suspension linkages & swingarm needle bearings repacked, ++.

I expected this would take care of the mystery "movement". Instead I had the real problem make itself known:

Limped home at 35mph. Ordered new OEM rotors because $92 each, and brake parts and seals I don't already have.

Question - OEM rotors are semi-floating, should the "buttons/bobbins" be "cleaned"? Should I be spraying the bobbins with brake cleaner & blow them out with the compressor a couple times a year?

FYI the web has lots of cleaning recommends for full-floating rotors, spinning the bobbins with a drill. That seems like a bad idea to my senses, and not for semi-floating rotors.

Wow. I've never seen a rotor fail like this. Did the bobbin collapse? Or did the rotor wear a hole in to it? I've never seen one shifted like this and trying to understand how it moved. 

[Pursuvant]

On 11/27/2023 at 2:37 AM, shinyribs said:

Wow. I've never seen a rotor fail like this. Did the bobbin collapse? Or did the rotor wear a hole in to it? I've never seen one shifted like this and trying to understand how it moved. 

I've been busy and forgotten this disc fail - all was fixed quickly. I will get the disc out again and try to get some measures on distortions - and see if a second review gives me fresh insight. At the time it "failed" I was very aware if I had been at high speed approaching a fast corner....

[shinyribs]

Just odd because the bobbins aren't collapsed, but the disc is certainly shifted on the carrier. Any chance it was just machined wrong and you didn't notice at first? 

[Pursuvant]

Anything is possible of course. But the front disks survived 85K miles being pinched by a Brembo corsa corta 17RCS/steel brake lines with the ABS disabled because I could out brake the abs and brake (slow the wheel rotation/decel) faster/harder without abs (choose your metaphor).

I will have to count how many sets of ebc hh pads I wore out in that time, and the serious forces that were in play each time I bedded new ebc pad sets to burn off the green fade.

I'm going to guess that the carrier just couldn't handle it any further.