Author Topic: Replacing the Roller Bobbins on Front Floating Disks  (Read 23485 times)

Offline frankenduck

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Replacing the Roller Bobbins on Front Floating Disks
« on: October 06, 2011, 01:04:09 PM »
4 valve K bikes have floating brake rotors in the front.  What holds the rotors onto the carriers are "Roll Pins." (a.k.a. "bobbins")  These are a wear item that need to be replaced periodically.  They will let you know when it's time to replace them.  At first you'll hear some slight rattling when backing your bike out of the garage.  As they get worse you'll start to hear them rattling when riding at low speed.  At a minimum, I'd suggest replacing them when the latter starts to occur but doing it sooner is preferred.

Each rotor is held to it's carrier by 12 roll pins, 9 of them are regular roll pins and 3 of them have an internal spring around them and are equally spaced at every 4th position.  The roll pins are #3 in the diagram below. On wheel side of the carriers/rotors are washers(#2) and E-clips(#4) that hold them in place.

There are three approaches to replacing them. The first is to do it with the wheels on the bike.  Personally, I wouldn't do that unless I had a bike lift.  The second approach is to remove the front wheel from the bike. (The rider's manual that came with the bike shows the proper removal and installation procedures for the front wheel.)

The third approach (what I do) is to remove the front wheel and then remove the carriers from the wheels and replace the roll pins on the workbench.  This makes replacing the roll pins very easy and also gives me a chance to get the inner parts of the wheels very clean.  If you take this approach, make sure that you are using a good Allen wrench (like the one in the factory toolkit) and that it is well-seated.  The carrier bolt heads tend to be a little soft and can strip easily if you are not careful.  Using a torch to preheat them or some Kroil (or other penetrating oil) prior to removing them isn't a bad idea either.

I use a small screwdriver to pop the E-clips off.  If you look inside the holes where the "springy" roll pins are, you will notice that the spring on the roll pin has caused some wear inside the side of the hole where it mounts.  It's a good idea to rotate the location of the springy roll pins by one hole when putting the new ones in.

The regular roll pins go back in easily but the springy roll pins can be stubborn due to the spring around the center.  I've found the compressing the spring around the roll pin with small needle-nosed pliers helps get the springy roll pins back in. In order to avoid scratching the rotor or carrier, I use a plastic tool (the rear end of a plastic pen) to push the E-clips back on.

I usually also replace the washers and E-clips but you could probably get way with using the old ones.

Parts required:
 
Diagram #QuantityPart NumberBMW Part Description
31834112310086Roll Pin
3634112310995   Roller with Snap Ring
224   34112310088   Flat Washer
424   34112310089   Lock Ring
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Offline Wescoe

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #1 on: January 18, 2012, 11:08:41 PM »
So my parts came in today and I went to the dealership to pick them up.  They alerted me to a discrepancy in the parts diagram.  Apparently there are no "Roller with Snap Ring," part no, 34112310995 listed for the ABS model  If anyone has replaced the bobbins on an ABS bike, can you please confirm or deny the use of the snap ring rollers on the left disk.  Thanks.

Offline frankenduck

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #2 on: January 18, 2012, 11:37:20 PM »
So my parts came in today and I went to the dealership to pick them up.  They alerted me to a discrepancy in the parts diagram.  Apparently there are no "Roller with Snap Ring," part no, 34112310995 listed for the ABS model  If anyone has replaced the bobbins on an ABS bike, can you please confirm or deny the use of the snap ring rollers on the left disk.  Thanks.

Show them this link and ask them to explain it:
http://www.bmwmcchattanooga.com/products/BMW-Motorcycles/ROLLER-WITH-SNAP-RING/1038925/34112310995.html

And it's both disks, by the way, not just the left one.  Not  to mention that ABS has nothing to do with it.
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Dug a hole and covered him up
Now I sit there by the hour
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Offline Wescoe

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #3 on: January 19, 2012, 01:06:00 AM »
Yup, they were reasonable about it.  The right rotor between ABS and non-ABS models is the same part number.  The left disk has different part numbers, at least in their computer.  They said they couldn't see any reasonable reason why there would be a difference between L/R and ABS/non-ABS disks. They told me to pay attention when I take it apart and make sure there were spring bobbins in each side. 

Just wondered if there was some previously gained wisdom floating around.

Offline johnny

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Offline F14CRAZY

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #5 on: October 26, 2015, 06:37:13 PM »
I've got maybe 1mm of rotational play...I take it I should replace mine before too long
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #6 on: November 30, 2015, 09:05:32 PM »
Hey Johnny,

Were your rollers making a lot of noise that alerted you to change them?
The pic shows them all mangled up. Was this the result of your extracting them? (I think I know the answer to this one)
One more thing, are the stainless cheaper than stock...(stock aren't stainless?) ? If not, what do you see as the stainless advantage?

Thanks
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Offline johnny

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #7 on: November 30, 2015, 09:46:33 PM »
greetings...

no noise... was just getting used to a little preload on the bobbins when fineesing the rs through the canyons of death...

then lior the tior man pointed out they were beyond whack and insisted they be replaced before my next ride... i agreed...

what you see is what i had on the moto... no damage when taking them off...

the stainless kit made more sense than the oem... they gotts 50 thou on them now and still look nearly new...

id getts them again...

j o

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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #8 on: November 30, 2015, 09:53:11 PM »
Johnny, thanks for that review. Motobins it is.
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #9 on: December 01, 2015, 11:46:48 AM »
Hi again Johnny,

***Did you take the wheel off or did you replace one ant a time with the wheel on the bike?

***The Motobins rollers/bobbins all look the same in their pic but the BMW kit, I believe, from Duck's description has a few that are different ...rollers with snap rings, so...did your kit have the roller snap rings?

(From their website: They are now black vs the stainless look you got...)

For those interested, it will now cost $98.62 to replace both discs...inc shipping through the Royal Mail - first class..(cheapest way)

Link to motobins rollers/bobbins       https://www.motobins.co.uk/bmw-parts.php?model=K%20Series&bikeref=K100
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Offline johnny

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #10 on: December 01, 2015, 03:14:31 PM »
greetings...

i recall them to be all the same... all c clip... no spring ones in the motobins kit... wheel off...

mark the disk and carrier... if you dont you will have to rotate the disk on the carrier until you getts all the bobbin holes matched up cause all the holes are not the same...

j o







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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #11 on: December 01, 2015, 04:24:18 PM »
Hi there Johnny and every0ne

Ok, The reason your old bobbins looked so bad is that they are made of Aluminum  :yow , as you might already know. Why are they made of that? Seems like an inappropriate metal.
Therefore, my guess is that the SS ones from motobins will last the life of the bike.
I spoke with motobins via email today and they said that the SS version does not need the circlips as the Alu version does and they are all the same.

I have read, can't remember where, that these things can be installed with the wheel on the bike. What do you think?

Thanks
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Offline Laitch

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #12 on: December 01, 2015, 04:35:54 PM »
The first post of this thread indicates that these parts can be installed with the wheel on the bike, beemrdon, but recommends using a lift for the attempt; however, that post was made four years ago.
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http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #13 on: December 01, 2015, 05:02:44 PM »
Laitch, Thanks for that.
I guess I missed it.
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #14 on: December 01, 2015, 05:16:05 PM »
I just remembered where I had read it. IBMWR KTech - Check it out.


http://www.ibmwr.org/ktech/floating-disk-rollers2.shtml

And

http://www.ibmwr.org/ktech/floating-disk-rollers3.shtml


 :clap:
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Offline Laitch

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #15 on: December 01, 2015, 05:20:02 PM »
Every successful memory retrieval is an unqualified victory! Congratulations!
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http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #16 on: December 01, 2015, 05:53:02 PM »
Aye-yup.    :clap:
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Offline Scott_

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #17 on: December 01, 2015, 05:59:13 PM »
When I replaced mine I did it with the wheel on the bike.

My impression of the Aluminum over the Stainless: The rotor to carrier is a loose fit, ie there is motion, friction, thermal expansion/contraction and wear. Compared to the cost of brake disks and the carrier(if even available), I'd rather pay to replace worn bobbins, than to have to replace the brake disk or carrier from egg shaped holes caused by the harder stainless bobbins....

Just my opinion. YMMV.

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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #18 on: December 01, 2015, 07:05:23 PM »
Thanks Scott,

That's an interesting take. hadn't thought of that.   Looks like that's why they are ALU.
I will talk to a few others on this to get a consensus.
Maybe Rusty at Max and the guy at Motobins

What was the mileage when you replaced them?

How many miles on yours since the replacement?

Has there been any change in the fit or looseness since the replacement?

Questions, questions, questions... :dunno

The BIG question, for me, is ....why floating rotors to begin with? They seem like more of a hassle than they are worth.
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Offline The Mighty Gryphon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #19 on: December 01, 2015, 08:24:57 PM »
Floating rotors are self centering in the calipers.

I changed mine at 108,000 miles.  When I did mine I did it with the wheel off since I was installing a new tire.  Wasn't that hard to pull the wheel, and it gave me a chance to detail the disc, carrier and wheel.  Also threw a coat of paint on the carrier to pretty it up.  New pads, stainless lines, anti-seize on all the fasteners and proper torque when I reassembled.  Looks and works like new.

I agree that aluminum is a lot easier on the disc and the carrier. 
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #20 on: December 01, 2015, 10:25:56 PM »
Yeah, thanks for the info MG. Mine work great too. Stops on a dime. They're just a bit loose and noisey.  76,xxx miles on the clock.
Don
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Offline Scott_

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #21 on: December 01, 2015, 10:38:26 PM »
I replaced the bobbins on the '95 around 104K miles, not long before I replaced the rotors.
I have no history prior to my ownership, so I really can't say if they were still original or not.

While I was changing them on the '95 I also went ahead and changed them on the '97 as well.
I probably could have left them be as they were only at 50K miles, but there was some wear so I changed them anyway.
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #22 on: December 01, 2015, 11:12:50 PM »
Well, I've got 76,xxx miles on the LT. The rollers/bobbins are loose. I can wiggle the disc a bit with my fingers and they are also noisy at times.

They definitely do not look totally shot like the ones in JO's pics.

*The bobbin thing is a part of my search to get rid of any sounds that I hear that are not the motor.
(I also hear something that sounds like an exhaust heat shield rattle on a car when backing off on the throttle. It is annoying and I can't locate it.)                 
                                                                                                 
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Offline The Mighty Gryphon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #23 on: December 01, 2015, 11:38:53 PM »
(I also hear something that sounds like an exhaust heat shield rattle on a car when backing off on the throttle. It is annoying and I can't locate it.)                 

Check where the bottom end of the clutch cable is relative to the muffler.  I can't speak for the 1100, but on the 75 the arm can just touch the top of the muffler and will make a clanking sound like a loose heat shield.  On the 75 you can hear it with the engine off by pulling the clutch all the way in and then letting the lever snap out.  You can hear the arm clank on the muffler.  Take up a couple millimeters on the cable and readjust the clutch pushbolt for the correct freeplay.  That fixed it on my bike.
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Offline beemrdon

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Re: Replacing the Roller Bobbins on Front Floating Disks
« Reply #24 on: December 02, 2015, 12:09:52 AM »
Thanks, I'll check it out.
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Tags: bobbins