Floating disc tolerance?

[BlitzenGruv]

I've read quite a few posts describing whack with these brakes. BUT, nowhere can I find a tolerance spec for the play on the bobbins.
I always assumed that the pulsing weirdness at low speed was due to the ABS. Then when I mounted a new front tire even the guy who did the work commented on how loose the disc felt.
Before I spend $150+ on new bobbins, what is the runout spec on these, radially and laterally? As an ex QC person, I deal in NUMBERS, not how it feels.

[koapono]

I can't speak to specs, truthfully I didn't look too hard as my rotors were wicked sloppy and upon removal the bobbins were pretty well worn and chewed up.
I bought my bobbins and rollers from outfit below at a substantial savings compared with BMW OEM prices.
replacement was easy enough and straight forward.
make sure when you order you get 9 bobbins and 3 rollers (these have a spring ring around center) per wheel, total of 18 and 6 each.


https://www.euromotoelectrics.com/product-p/brotorroller086.htm

[Scott_]

I don't seem to recall reading of a specific "spec", other than a visual inspection of the actual bobbins.
The stock ones are aluminum so they will show signs of wear, they were designed as a wear item.
Remove them one at a time and look at them, if they are hard to remove because they have a wear groove in them, then I'd suggest you replace them, if they don't show signs of wear, then you are fine for now.
You will find that approx 1/3 of them are a special bobbin with a special 'spring ring', these will a bit more challenging to remove, but it can be done.

[volador]

No mention of it in K1100 repair manual just

Front wheel
minimum thickness 4.5mm

Rear wheel
minimum thickness 4.6mm
permissible lateral runout 0.2mm

[Laitch]

As an ex QC person, I deal in NUMBERS, not how it feels.

Sometimes feelings are more important—adapt or die. EBC considers axial play a detriment. I haven't found numbers yet and am quitting the search.

[alabrew]

Mine were purdy sloppy and rattled. Some were purdy chewed up.

I gotts new ones from some indy guy in the EU, can't remember the name, but found it here.

Purdy easy to replace.

[johnny]

greetings...

here is a visual aide...

nawt good...


IMAG0197.jpg (32.73 kB . 432x576 - viewed 476 times)


IMAG0222.jpg (36.65 kB . 768x576 - viewed 415 times)

good...


IMAG0224.jpg (29.92 kB . 432x576 - viewed 404 times)

j o

[Hilltopper46]

This would be a good project while one is practicing social distancing. But then, riding the brick would be a good practice while social distancing.

greetings...

here is a visual aide...

nawt good...

good...

j o

[BlitzenGruv]

Thanks Johnny.
Mine don't look anything like that bad. It's just that the radial play is so much that I'd like a concrete tolerance before I drop a lot of cash and time to replace them. Maybe that much slop is how they're supposed to work? I don't know all my other vehicles have fixed discs.
One would think that those anal Germans would publish a +/-

[Laitch]

One would think that those anal Germans would publish a +/-

Maybe they didn't realized the anal-ness of some Americans demanded satisfaction. 

Anyway, here's something wrtten in German for you.

[koapono]

if they're sloppy, replace them.
they will just wear more with each application of brake.
though mine (recently replaced) were not as bad as the ones JO posted, they were worn and starting to deform.
you can remove a couple from wheel while it is still mounted and inspect them for confirmation before purchase.

[alabrew]

I went looking for those bobbins I bought, butts didn't find them. Want to say TMG posted the link, maybe he still has it.

I did run across a thread where filmcamera replaced his and reported a .25mm movement with new.

[Filmcamera]

Here is the page they are on at Motobins


https://www.motobins.co.uk/bmw-parts.php?model=K%20Series&bikeref=K100


You should probably check they are the right ones for your model.


I did change mine but ended up getting complete new discs in the end.

[The Mighty Gryphon]

I went looking for those bobbins I bought, butts didn't find them. Want to say TMG posted the link, maybe he still has it.

I did run across a thread where filmcamera replaced his and reported a .25mm movement with new.

This link?

https://boxer-upgrades.webs.com/apps/webstore/products/show/3821625

I have it bookmarked.  Past experience seems to indicate that having a source for reasonably priced parts bookmarked on my laptop is almost as good as actually having the parts in the garage when it comes to preventing part failures.

[alabrew]

I didn't keep it because I never thought I would need them again and in a way have them bookmarked on TMG computer and I can get it by asking =-}

He noted: Check the brake rotors on your bike, side to side play is normal, but if the discs turn clockwise or anti-clockwise, that is not OK.

[The Mighty Gryphon]

I didn't keep it because I never thought I would need them again and in a way have them bookmarked on TMG computer and I can get it by asking =-}

Having them bookmarked on my browser didn't prevent your bobbins from wearing out, did it?

Meanwhile, mine are nice and snug.

Hope you learned something today.