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New Bembo front disks and pads - vibration when braking?

Hi,

I put a new set of Brembo disks and pads on the R12S the other week but only got round to riding it at the weekend where it would vibrate when braking and cause a little pulsing on the brake lever.

These new brembo series oro disks are a 0.5mm thicker, and the replacment brembo bobbins (# 98.8247.20) were different in that they go on the wheel stalks 'upside down' i.e. top hat on the stalk.

After putting it all back togethor, I noticed that the pads were touching the disk and that it was a bit more difficult to push the bike around.

I checked all the bolts to make sure I had not left one silly-loose but all looks OK.

The disk was very hot after about 20 miles.

So I'm looking for ideas, two which occured to me were:

1. Did I managed to get some copper slip on the surface of the brake pad?
2. Should I get my calipers rebuilt to make sure they have full travel (78K miles on the bike)

On the return journey the next day The brakes were making a lot of noise when braking at slow speed - not squeeling more like rubbing / groaning noise.

The vibration on braking and a little pulsing of the brake lever seems to be getting better.

Thoughts?

Cheers

Adrian
Old 05-29-2018, 06:05 AM
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I know this is not a solution, but what if you were to put the old worn brake pads back in for a trial .
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Old 05-29-2018, 06:59 AM
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Hi,

I've not bought the special tool to push back the caliper pistons, so I use a pair of long nose pliers which I push into the space between the old pads and twist them through 90 degrees to push the pistons back in.

This has consequences for the old pads - I'm not sure I'd want to put them back in now with the indentations they have.

Cheers

Adrian
Old 05-29-2018, 07:17 AM
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Looks like your pads are dragging on the pin. Better take a look on this quickly as you risk ruining the overheating disc.
Old 05-29-2018, 03:15 PM
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Anti chatter clip in?
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2006 Subaru WRX STI S204 #318 / 600
Old 05-29-2018, 03:58 PM
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Maybe the 'upside down' top hat is causing a clearance or , not centered problem ?
A photo would be nice.
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Old 05-29-2018, 04:18 PM
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Did you follow the the 2 step torquing procedure and not over torque the bobbins / wave washer? Spacer washers replaced between the disc and wheel or are these not necessary anymore with the .5mm thicker disc?
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Last edited by BikerMiker; 05-29-2018 at 05:52 PM..
Old 05-29-2018, 05:48 PM
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Hi everyone,

I copper greased the pin before slotting it back in with both anti-clater devices in place (and the right way up).

The dragging on the disk does trouble me, I think I'll reassemble it all again and check the travel on the pistons.

For the bobins, I bought new items all round as I wasn't keen on reusing the factory parts at this stage. The new bolts (+bobbins) I got from the local Brembo dealer (biketorqueracing.co.uk) were of the stainless steel type using a standard hex-head rather than a toque bit.

I got them all finger tight in the cross diagonal way then tried to torque one up using my trusty old torque wrench to the suggested value of 24nm - but all it did was round out the hex hole on the bolt.

So I took the wheel back to biketorqueracing asking them had I done something wrong. Turns out my trusty torque wrench is in need of recalibration. I also learned at that point that stainless is much softer and should only be torqued to 20NM.

So they cut a new surface on the rounded bolt and we got them out and I bought a new torque wrench on the way home. and torqued them up to 20NM (but I could feel the heads starting to deform)

The shops take on this was that they sold hundreds of these bolts and had no issue.

So that was my bolts dilemma.

Cheers

Adrian






Old 05-30-2018, 12:26 AM
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Does the disc rest on the bottom lip of this bobbin?

If it is as thick as it looks in the picture, I would guess that both discs are being
pushed out too far away from the wheel if the discs indeed are resting on the lip of
that retaining bobbin. That will subtly misalign it with the calipers, putting pressure on the
outsides of each disc against the outside pads. My rotors currently sit on directly on the "stalks" of the
wheel. I can't remember if one side has .5mm spacers or not but there is no
thick washer or bobbin in between the disc and the wheel/ABS sensor.

Also the torque procedure 12nm for the first stage and 24nm for the final.
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Old 05-30-2018, 09:14 AM
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Quote:
Originally Posted by BikerMiker View Post
That will subtly misalign it with the calipers, putting pressure on the
outsides of each disc against the outside pads.
I've been thinking about this.... Now I'm not sure if the calipers should adjust to that condition or not.... Maybe someone else would know for sure.
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Old 05-30-2018, 12:14 PM
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Hi,

I've not got ABS, so they just sit on the stalk of the wheel, the disc fits over this, then the wavy washer, then the final washer which is slightly counter sunk to allow the bolt to 'align' into it. (I think that's how it was - I'll check and post again)

I'll get e a photo of it when I take it apart this weekend, along with the caliper/rotor.

I'm going to give motor works a call as well in the UK, as they have some warnings about pre and post 2007 bikes, with 2007 having 'permanently attached bobbins'.

Bike Torque told me these were to adapt the earlier wheels to fit the later disks.

Mmmm.

Cheers

Adrian
Old 05-31-2018, 10:12 AM
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2008 GSA BREMBO DISC REPLACEMENTS FRONT

"The change to the newer mounting system moves the discs 2mm further outward and the brake callipers are machined with 2mm less mounting boss to match.
Putting the old style discs and mounts on mean your discs will be 2mm further inboard and not run central in the calliper.
Still works though.
I ran the same setup but I also had 2mm spacers made up to move the calliper inwards"

Someone else had an observation to make about the 'center line' of the calipers too....
Old 05-31-2018, 10:20 AM
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it might be that my pistons need to travel in places they have not been before...
Old 05-31-2018, 10:21 AM
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I should mention that on my 2006 there was a washer on the stalk of the wheel that the disk sat on. (a change from my 99 R11S where the wheel became a wear item)

I'll need to find some of these to work out if it is the same thickness as the new bobbin 'top hat ' that replaces it.
Old 05-31-2018, 10:32 AM
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We have worked out what happened.

Bike Torque sold me Brembo Part 105.5776.15 which is correct for model year.

But they actually gave me 105.5776.12 which is in the bucket next to 105.5776.15.

105.5776.12 is for the later models which have bobbins attached to the disk and a different offset for the caliper.

The photos I've taken show that one pad is flush against the caliper and the other is extended (red circle).

This pushes the disk against the outer pad.


Old 06-01-2018, 03:23 AM
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Hi,

Got the correct bag of parts this time and it all works as expected.

However, the [correct] replacement brembo part did not come with very thin washers which cover the wheel stalks the disk sits on.

I re-used these parts as I was concerned about the R11S:

https://forums.pelicanparts.com/bmw-r1100s-r1200s-tech-forum/78433-front-wheel-brake-disc-mountings.html

I then looked at REALOEM to see what they were and could not find these washers on the system - it looks like it only shows disks with bobbins mounted in them:

RealOEM.com - Online BMW Parts Catalog

I'll phone BMW and ask.

Adrian
Old 06-04-2018, 11:59 PM
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