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Very loose floating Brembo disc

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andyisavinit View Drop Down
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    Posted: 04 Aug 2022 at 22:26
So I've started to notice a pulsating under braking. More noticeable at slower speeds. Not through the lever, but the whole bike. Bike's a gen 1 mille R.

Just starting to investigate things...the left floating part of the brake rotor is very loose, literally making a knocking noise as the wheel spins. It has a lot of lateral movement of about 1mm (maybe a bit more).

This is obviously too loose. Ive got another pair of rotors and the only bit that moves is the round bit that turns. Can these be tightened up? Why has it become so baggy? Could this be the cause of the pulsing? 

Just to add -  the pad wear seems even but I haven't checked the calipers properly as yet. Eyeing down the spinning rotors (not using any measuring tool) they don't look significantly warped or discoloured either.

Here is a video...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wigginsjp Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2022 at 07:19
Hi 

They do wear naturally and cannot be tightened only replaced. 

I’m not sure what the acceptable movement is on the disc bobbins for an mot, but I’ve some virtually new fully floating discs with anti rattle bobbin dampers that can’t be far off yours. However, they are fully floating discs and not semi floating discs. You have forward and backward movement to account for as well as side to side. 
Grab a new set of Brembo off Griff at AP and see another 20 years. 
The sunstar discs Aprilia put on the later Gen2’s had a fair amount of movement from new. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2022 at 07:20
I doubt it’s the cause of the pulsing alone , more likely disc run out but whether it’s excessive might depend on the disc. I do remember that the sunstar versions had tons of float but Brembo not much at all. Are both sets the same brand ?

Might be worth swapping just to prove if your on the right track. 
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andyisavinit View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyisavinit Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2022 at 18:19
Yeh I’ll fit the other brembo’s I’ve got and see if that changes anything. It was 10pm so decided not to last night. I wanted to get your take on the floating discs. But I think you’re right. It won’t be the cause of this pulsing. 

I will report back. 
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Rich Simpson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Simpson Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2022 at 18:25
When these floating discs first came out, I rode a Ducati 750 F2 with them fitted.

Twenty miles of dual carriageway with them rattling like the tambourine in a primary-school orchestra, and they'd knocked the pistons back into the caliper. Luckily there was nothing coming on the roundabout.

The discs on my  Mille don't move....but I can't see what the point of floating discs was in the first place. Surely you want the wheel hub to act as a heat sink, not insulate the disc from the wheel and let it flail about?

If the rotor itself is warped then letting it float from side to side won't help. And there's a load of components in there to fail and kill you.

Am I missing something, or is it just 'blingineering'?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowman Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2022 at 20:40
If it is the discs I replaced mine with bermbo oro discs cured my pulsating lever ( which any new disc would) they are 0.5 mm thicker , also fitted SBS pads , been fantastic since but not cheap, oh the centres are black not gold but there . Good luck.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyisavinit Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2022 at 08:03
Well I changed the left rotor due to the loose floating disc, the right disc looked as though it was warped (when I spun it, it was waving a bit (max run out in the book says 0.3mm)) so I changed that too. I cleaned the calipers and made sure the pots were all moving smoothly.

The bike is still bouncing under braking – it's only noticeable from 15mph down to a stop with very light braking. Starting to think suspension. I'll give it a couple of clicks on the rebound and see if that works. I didn't change the pads, but can't see why that would be it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote redratbike Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2022 at 08:11
are you running a steering damper ?
disconnect that to see if it cures the issue 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote legend88 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2022 at 08:40
Bouncing or juddering?  Headstock?  (Easy to check)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IanG Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2022 at 14:24
Perhaps clean the disc surfaces with a suitable tool to remove any localised build-up of pad material?  That can lead to pulsing even if the disc is true.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyisavinit Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 18:23
Sorry been away for a week. Back riding now. 

First ride for a week - it’s much worse now!!

I would now say yes, it has progressed to a judder. Noticeable at all speeds under all breaking conditions (lightly or harder braking). 

Applying the brakes at around 70mph it’s like a jack hammer. Slowing with speed. 

Head stock check then. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Simpson Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 20:01
Perhaps this is too obvious a question (sorry it it is), but did you carefully clean the hub mating surfaces before installing the discs?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyisavinit Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 20:48
Originally posted by Rich Simpson Rich Simpson wrote:

Perhaps this is too obvious a question (sorry it it is), but did you carefully clean the hub mating surfaces before installing the discs?

I remember cleaning one side very well. But now you mention it, I didn’t spend too much time on the other side. If all else fails I’ll go back. 

Well I’ve just checked the head bearings and they didn’t seem loose at all. But still gave it a 1/16 of a turn. Test ride- no difference. Suns going down and can see the headlight bouncing as I come to a walking pace. Maybe now a little weaving so I’ll back that off again. 😡

Backed off the steering damper all the way and no difference. 

New pads next. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Simpson Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 21:45
Change fork oil and or adjust suspension?
Check front wheel is correctly fitted
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 426hemi Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 22:02
As Ian said earlier clean the disc surfaces, pad material can build up and cause grabbing, scotchbrite and brake cleaner works well or a rotor honing tool in a drill is the best.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote andyisavinit Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 22:29
Right! I might be jumping the gun slightly but I changed the pads and went for a quick spin through the neighbourhood. No fairings no shorts not much time. 10pm. 

I think it’s the pads. I’ll have a proper ride tomorrow to confirm but it felt good. They need to bed themselves in a bit obviously. 

This is where I hang my head in shame. 😔 When I cleaned the calipers I didn’t check the brand of pads. I just looked at the wear and thickness. They were running low but me being a tight arse I thought I could get a few hundred miles out of them. 

Turns out they are brembo pads and could well be, most likely, the originals. NINETEEN YEARS OLD!!

I’ve fitted some ebc ones. 

  I’ll let you know tomorrow. Sorry, I feel bad for wasting your time thinking of solutions. Well I hope I’m right. And if I am well thanks for the thoughts, at least I’ve given the front end a good check over. 

🤪
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rich Simpson Quote  Post ReplyReply Direct Link To This Post Posted: 15 Aug 2022 at 22:38
If you've changed the discs, it's always good practice to change pads at the same time
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Post Options Post Options   Thanks (0) Thanks(0)   Quote redratbike Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2022 at 08:02
don’t worry about wasting out time LOL

hopefully you have it sorted 


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