Replacing brake rotor bobbins only = safety issue???

[Theophilus]

I have a 2000 R1100RT, bought in October 2006. Clock currently shows approximately 34k. This is my first bike, and has been a joy (and sometimes a handfull) thus far.

 

After being told by my friendly BMW service manager that my front brake rotors were thin and needed replacing, I measured them myself at several locations and found that I was much closer to 5 mm (the new thickness) than to 4.5 mm (the minimum, or limit, thickness) on both front rotors. My bike is an R1100RT, so it has the floating rotors with bobbins.

 

When I told him the rotors were not thin, he said they were loose and said the only fix for that was to replace the entire rotor assembly, and that the bobbins were "press-fit" at the factory or some such explanation.

 

After reading the myriad posts here regarding bobbin replacement, I am less than happy with the information I am getting from the BMW man. When I pointed out that the bobbins are indeed replaceable, he then said that none of his mechanics would do the job because it would be a potential safety hazard. Apparently, the claim is that the carrier wears as well as the bobbins, and the right thing to do is replace the whole assembly. Since I have lost almost no meat from my rotor wear surfaces, I am reluctant to do this and am considering replacing the bobbins myself, although I have never wrenched on a motorcycle in my life.

 

This newbie would be interested in any insight regarding the potential safety aspects; I have already read enough posts to know that the job is very do-able, where to order the parts, what to expect, etc. What I did not find was a safety-based discussion, and that is my particular interest in this case.

[smiller]

Your service manager is dead wrong on just about everything related to this topic and there are no safety issues related to replacement of the bobbins assuming it is done correctly, and it's pretty hard to do it wrong. The bobbins are much softer than the discs or carriers and neither of these will wear significantly, the only possible issue being to offset the spring-loaded bobbins by one hole when you replace them (as you've probably read in the other threads.) Replacing the bobbins is all that is required and once completed the rotor assembly (assuming that the rotor itself is not below an acceptable thickness, and yours appear to be fine) will be nearly as good as new.

[glwestcott]

I think I would get another opinion. With only 34,000 miles on the clock, I doubt there is anything wrong with the rotors or bobbins. I have 72,000 on my 2001 R1100RT and have never done anything brakewise other than change pads and drain fluids. Rotors are still fine.

[smiller]

With only 34,000 miles on the clock, I doubt there is anything wrong with the rotors or bobbins.

That is also a good point. As mentioned in the other threads on this subject, a little axial (in-out) play is normal and nothing to worry about. The bobbins only need to be replaced when there is significant radial play and that usually takes considerably more than 34k miles.

[Edgar]

What city was this dealer located in, as we need to avoid them.

[David]

If they wear significantly, it could be a safety issue, but there's no way you're anywhere near that point. If you understood your BMW guy appropriately, he sounds like an incompetent tech or a thief. Neither gives me much confidence.

 

I replaced mine (on an 1100RT) at 51k, not because of safety but because they annoyed me when reversing with the wheel turned. It's time consuming but very simple to do. I didn't even take the rotors off.

[keithb]

Boy I do not enjoy reading this type of post. You are being fed misinformation my friend (I changed my original comment- it would have been edited out). I had a similar experience myself with rotors and tolerances, etc. at a dealership. There was an article in the BMW MOA magazine about replacing the bobbins several years ago and basically said they go bad in the 40K-50K mile range which is right on at least for my bike. You want the rotors to float left to right but you don't want them to float front to back on the bike. I had to change the bobbins on my K11RS at the 45K mile mark. You can order the parts for about $85-$100 (Chicago BMW/$85) and do the job yourself. It is easy. Remove the wheel, then the rotor and replace them. I put everything back together exactly the way I took it apart. The whole job took about 1 1/2 hours.

[DavidEBSmith]

When I pointed out that the bobbins are indeed replaceable, he then said that none of his mechanics would do the job because it would be a potential safety hazard. Apparently, the claim is that the carrier wears as well as the bobbins, and the right thing to do is replace the whole assembly.

 

Funny, there are parts like the brake master cylinder that BMW sells as a unit to avoid issues with piecemeal replacement. Yet BMW sells the bobbins separately. Hmm.

 

I'm not entirely sure that the need for bobbin replacement isn't just a bit of BMW owner folklore. I've done it on two front wheels, and it is a bit creepy when you can feel the rotational looseness of the front brake. But I've never heard of anybody wearing out the bobbins to the point that the disk fell off or something. And I've certainly never heard of any of the handful of people who've replaced the bobbins having any problem with them. How many would have to fail before the disk would come off the carrier?

 

Anyway, the rotors on your bike are supposed to be a little loose. If they aren't a little loose, they'll warp. I have two front wheels; one where the rotors are really tight (and warped) and one where the rotors rattle like a handful of pebbles in a tin can. I replaced the bobbins on each wheel when I could grab the rotor like a steering wheel and twist it left and right. Replacing the bobbins didn't have any noticeable effect on the radial looseness of the rotors or on their noisiness.

 

And the two sets of rotors have 150K miles between them, and aren't at the wear limit yet.

 

Yes, the carrier wears a bit. But it's hard steel and the bobbins are soft aluminum, so they wear much more. They're actually surprisingly flimsy for something holding your brake disks on, which leads me to believe that the chances of having a problem with them is even less than you would think. Bobbin replacement is an easy hand tool job. You could even do it with the wheel on the bike, although it would be an obnoxious job. Easier to remove the wheel so you can turn it the way you want. Easier still if you can get the carriers off the wheel and do it that way.

 

But at 34K miles, I wouldn't think you need to replace bobbins yet. Grab the disk like a steering wheel and steer. If it moves rotationally, replace the bobbins. If not, if it only moves in and out along the axle, don't replace the bobbins.

[Bonkorama]

I recently replaced ALL of the bobbins ( the dealer calls them spindles here in LA) just 2 weeks ago. There are 2 different types on your rotor. Its not obvious untill you remove them. One bobbin has a wire clip, and one doesnt not. There is a little machined groove on the bobbin that the wire is wound around, there are if i remember correctly 4 on each rotor, spaced evenly every 3 or so...

the other bobbins have no wires. After you remove a bobbin, you can look in the hole where it used to be in the rotor and see a matching little groove. If you find a groove in there, that is where the bobbin with the wire belongs.

 

I didnt remove the wheel or tire to do mine.

 

if you have this tool: E-Clip reover - installer you will make this job a ton easier.

 

Also buy yourself a pair of L O N G needle nose pliers.

 

Its a few hours work, but you can put the radio on and relax. Its a no brainer. It can be a knuckle skinner, but thats an added bonus if you ask me.

[Joe Frickin' Friday]

After being told by my friendly BMW service manager that my front brake rotors were thin and needed replacing, I measured them myself at several locations and found that I was much closer to 5 mm (the new thickness) than to 4.5 mm (the minimum, or limit, thickness) on both front rotors. My bike is an R1100RT, so it has the floating rotors with bobbins.

 

When I told him the rotors were not thin, he said they were loose and said the only fix for that was to replace the entire rotor assembly, and that the bobbins were "press-fit" at the factory or some such explanation.

 

After reading the myriad posts here regarding bobbin replacement, I am less than happy with the information I am getting from the BMW man. When I pointed out that the bobbins are indeed replaceable, he then said that none of his mechanics would do the job because it would be a potential safety hazard. Apparently, the claim is that the carrier wears as well as the bobbins, and the right thing to do is replace the whole assembly. Since I have lost almost no meat from my rotor wear surfaces, I am reluctant to do this and am considering replacing the bobbins myself, although I have never wrenched on a motorcycle in my life.

 

I would not trust anything that mechanic tells you ever again. As David said, he's either incompetent or dishonest, neither of which is acceptable.

 

This newbie would be interested in any insight regarding the potential safety aspects; I have already read enough posts to know that the job is very do-able, where to order the parts, what to expect, etc. What I did not find was a safety-based discussion, and that is my particular interest in this case.

 

You'd have to wear the bobbins down pretty far before there's a safety issue. The issue, I think, is about the wear progressing to such a point that the rotor can get cocked badly out-of-plane so that it binds in the caliper, or the braking forces cause further misalignment/buckling of the rotor and pins, all of which would be undesirable. People change them long before that point because the rattling just gets annoying.

 

BTW, welcome to the board. If you've never wrenched on a motorcycle before in your life, I'd recommend you keep your eyes on the Ride/Event Planning forum for a Tech Daze near you. It's a good chance to meet people from the site, and you'll learn a lot about your RT from people who have a lot of experience wrenching on it; it can be very helpful/encouraging to have a second set of eyes watching over your shoulder to help you through the tough spots and make sure you don't do anything you'll regret.

[topdal46]

What Dealership is this????

[JohnBeaven]

I replaced the bobbins on my R1100RT at about 100000km. It is an easy job but fiddly - took me about one hour to do the first side and 30 minutes to do the second. The trick being to remove and replace the bobbins one or two at a time.

[Theophilus]

What city was this dealer located in, as we need to avoid them.

I have received a hand-signed letter from the owner of the dealership in question asking about the service I received. I have some reason to believe that he is conscientious and will take steps to correct the problem. I am going to correspond with him first and see how he responds to my concerns. If you have an immediate and specific concern regarding an upcoming repair visit in Texas, please PM me. I will update the board on my progress.

[AviP]

I have a 2000 RT too. I checked my brake pads and rotors during my last service. But what are these bobbin thingies? Can somebody point it out in a photo or parts diagram? TIA.

[Joe Frickin' Friday]

I have a 2000 RT too. I checked my brake pads and rotors during my last service. But what are these bobbin thingies? Can somebody point it out in a photo or parts diagram? TIA.

 

look closely at your front brake rotor. The "bobbins" are a series of 12 small circular objects, each about 3/4" in diameter, arranged on a circle that is about 6-8 inches in diameter. Grab the edge of your brake rotor and wiggle it side-to-side; the bobbins are the pieces that loosely couple the rotor (the wear surface that the pads grip) to the carrier/spider (the central piece that actually is bolted to the rim).

 

Red arrows here point to 'em.

 

 

Note that '02 and later BMW bikes don't have these, and none of them have bobbins on the rear rotor.

[keithb]

I don't have a picture but will try to explain. When you look at the rotor it looks like two halves. An outer half and inner half. These two halves are held together by these bobbins. They are metal, round, and hollow. These bobbins are supposed to move side to side across the bike or left to right. If you try to pull the outer half of the rotor towards the front or rear of the bike and the bobbins have a lot of play in them they are bad and need to be replaced. As stated earlier they typically go bad in the 40K-50K mile range and should be replaced. Replacement cost is approx. $85-$100 for the bobbins. I hope the explanation makes sense.

[bmwmick]

I recently replaced ALL of the bobbins ( the dealer calls them spindles here in LA) just 2 weeks ago. There are 2 different types on your rotor. Its not obvious untill you remove them. One bobbin has a wire clip, and one doesnt not. There is a little machined groove on the bobbin that the wire is wound around, there are if i remember correctly 4 on each rotor, spaced evenly every 3 or so...

the other bobbins have no wires. After you remove a bobbin, you can look in the hole where it used to be in the rotor and see a matching little groove. If you find a groove in there, that is where the bobbin with the wire belongs.

 

This is INCORRECT! Go do some reading on the following link:

http://www.ibmwr.org/ktech.shtml page down to brakes.

 

IF you put the spring bobbins back in the holes with the groove worn in the carrier side, they will be almost impossible to get out the next time you do it.

 

You want to rotate the spring bobbins one hole away from where you remove them just to prevent the wire from sticking in the groove.

 

Mick

Tucson

[Bonkorama]

Thanks Mick for the info...

 

Shiver me timbers! This is why it must have taken me sooooooo long to get mine out the first time!

Of course I didn't think to look in a manual to see if the originals were put in wrong.

 

Sheesh.

 

Well, I got them out the first time, and the wires were worn to a hair's thickness on some. But it was the e-clip that was so stubbornly frozen on many that it took hours and hours of painstaking knuckle boneing work to get them off. I could NOT find an e-clip remover tool A N Y W H E R E untill of course i had completed the job using a super long & skinny flathead screwdriver i bent at a 30 degree angle and a pair of long needle nose pliers to help get the clips off.

 

Well, when i replace them again at 200k I'll make sure the right ones are in the right holes.

 

[JerryMather]

I didn't have to do this on my RT but, I have replaced all the front rotor bobbins on my Ducati to turn them into full floating rotors from the stock semi-floating rotors.

Basically it's the same thing for both BMW or Ducati. Unfortunately Brembo,( Ducati rotors), do not sell replacement kits to do this but they can be had through aftermarket manufactures.

The way I did it was to remove the rotors from the wheel and drilled out the center bobbin using a drill press, making sure not to drill any of the rotor.

 

WARNING: After installing the new bobbins with the E Clips, recheck them after rides. I lost one of the E Clips but not the bobbin within a 100 miles after I installed them.

[Theophilus]

What city was this dealer located in, as we need to avoid them.

I have received a hand-signed letter from the owner of the dealership in question asking about the service I received. I have some reason to believe that he is conscientious and will take steps to correct the problem. I am going to correspond with him first and see how he responds to my concerns. If you have an immediate and specific concern regarding an upcoming repair visit in Texas, please PM me. I will update the board on my progress.

 

Today, I received an unsolicited phone call from the General Manager of the establishment, who wanted to find out what had happened. I was planning to reply to the owner's letter, desribing the situation, but had not yet done so. So this is a welcome display of initiative on their part. I will continue to keep the board updated on progress.

[Dan Gleebitz]

Have a look at this site ... lots of photos and a blow by blow account ... http://www.ebbo.org/brake_discs.php