BMW R1200 / R1200GS Rear Wheel Carrier / Brake Disk Flange
See also: R1200GS Torque Settings (and scroll down the page that opens for service/maintenance schedules)
Always refer to the relevant manufacturers instructions and/or BMW workshop manual – usual warnings apply! Disclaimer
EBC Brake Shop – market leading EBC replacement brakes for BMW motorcycles – see here for DISCOUNT codes
BMW R1200 / R1200GS Rear Wheel Carrier / Brake Disk Flange
Comment: by Keiron M 03/2011: I agree this problem may still exist. My 2005 model with 52000 kms to date. Changed rear brake flange at about 42000 kms had all “fingers” where disc is attached cracked. Just had rear wheel off for tyre change. Have now noticed two “fingers” are now cracked again! Bike is a street use bike, a bit of gravel road occaissionly. Some say water may cause problem, if thats the case it is a design problem. As far as over torque , I used a torque wrench and changed last one myself.
Inspection of the rear wheel / brake disk flange for cracks* and how to change the rear wheel carrier / flange.
* There have been a few cases of the rear wheel carrier / flange developing cracks in the lugs securing the rear brake disc to the flange (from the threaded holes for the brake disk retaining bolts). See the discussions on ukGSer.com here: R1200GS Flange defect, take note and here on ADVRider.com: 1200GS Rear Disk Flange Cracks?
A number of possible causes are considered in the discussions mentioned above although to date I don’t think anyone has come up with the definitive answer. Interestingly BMW have modified the flange in some way and the original part number has been superceded with this new part number: C126.96.36.1999.631 (USA P/N: 33117694910)
Inspection – If you have cast alloy wheels the brake disk mounting lugs on the flange can be seen easily (circled in red above) through the wheel as you rotate it without the need to remove the wheel. For bikes with spoked wheels, the wheel hub is a larger diameter and obscures them so you need to remove the wheel to check the flange lugs for cracking.
This is what you’re looking for:
Above photo by ADVRider AldenB (Update Feb2010: “Just to up date you and the guys @ UGSer.com, while changing tires yesterday I checked the flange as usual and two of the lugs are cracked. Called the dealer and now they want the bike for a couple of weeks to show the factory rep…….Here we go again!“
And I’ve also seen a case of the flange / carrier having cracks from the wheel bolt lugs mentioned on ADVRider.com – most likely due to overtightening of the wheel bolts (torque wrench;-)
NB: IMPORTANT Also check the wheel for play, to check for wear of the flange splines / final drive wheel axle splines and/or final drive bearing wear. Whilst the flange to axle fit should be a tight ‘friction’ fit wear can occur which could prove dangerous if not identified. See here:
The following article is based on posts by ukGSer ‘Pukmeister’ (Adam) in the ukGSer.com thread mentioned above.
BMW R1200 / R1200GS
Installing a new rear wheel carrier / rear brake disk flange
I went out to check my 2004 R1200GS. The three ‘arms’ I could see through the rear wheel easily on my rear brake disk/wheel hub were fine (as I expected). But I turned the wheel to see the remaining lugs and to my horror, the other two arms had the cracks!
When I recently changed my rear disk, due to warping with a tight spot, I did a cursory glance rather than a proper good eyeball. I’m normally a stickler for all things engineering so can’t believe I didn’t find this earlier (unless its only just occurred). In hindsight, it may have been the cracked brake disk hub that allowed the disk to warp or the warped disk that stressed the carrier/flange lugs?
Either way, a trip to Bahnstormer Motorrad was called for to ask them about possible goodwill or discount on a replacement hub. This sort of failure is not good on a component which is meant to stay together for the life of the bike and its failure could have potentially life-threatening consequences. (AndyW: NB: no catastrophic failures known of to date).
My local dealer had never seen/heard of this happening and took a look out of interest. Eyebrows were raised as the same flange is fitted to the entire R1200 motorcycle range plus the K1200 model range.
A replacement ‘flange’ under the new part number of C188.8.131.529.631 for £115.99+vat (£133.38) was ordered as the old part is no longer available ( I wonder why??).
The photos below show my jury-rig of a cheapo 3 leg puller with an old metal test piece from my apprenticeship days as a plug in the hollow spindle to give it something to pull on. Note that it has to be pulled off-centre to get the 3 legs around the 5 armed flange. I heated the flange with my Turbotorch taking care to avoid the ABS sensor and wiring. Once hot enough to expand the flange, it easily slid off the splined rear drive hub with little effort. Without the application of heat it would never have come off as it is an interference fit.
Edit=AndyW Quote from the BMW Workshop Manual (RepRom):
BMW special flange removal tool / puller
Attempts to install or remove the wheel flange without applying heat can result in damage to the coating of the wheel axle. Always heat the wheel flange for removal or installation. If a new wheel axle or a new final drive is installed, the wheel flange has to be replaced at the same time.
Release temperature, wheel flange, rear-wheel drive – 100/110°C
Installation / fitting a replacement carrier/flange: Heat the wheel flange to the mating temperature, if necessary allow the axle to cool.
Mating temperature, wheel flange, rear-wheel drive – 100…110 °C
Mating temperature, wheel axle, rear-wheel drive – max 30 °C
Using the mark for alignment, mount the wheel flange on the axle by hand and without lubricant. The wheel flange must slip into position easily.
Attention: The rear wheel cannot be installed correctly if the circlip is installed wrong way round. In addition, the wheel flange can move and cause the brakes to overheat. Make sure that the circlip is correctly seated.
Install circlip (1), making sure that it is correctly seated in the groove. The circlip snaps into position with an audible click.
Second picture below shows the naked splined drive hub once the flange is removed. The yellow spots next to the rear bearing seal is granular rock salt thrown up from the roads. How did that manage to get in there ?? A scrub with some WD40 and an old toothbrush was in order.
And heres the new versus old flanges shown in the pics below. Note the new item has a fibre thrower ring bonded to the flange, whereas the old part is simply a large diameter section of the flange metal. That appears to be the only difference, the brake disk mounting lugs are the same thickness.
The final two pics below show the cracks in the arms of the flange where the rear brake disk mounts. The first pic isn’t too obvious but the crack is directly above the shadows edge. The second pic of the other lug is obvious.
Fitting the new flange is easy enough, just heat in a domestic oven to 100 degrees centigrade then slide it onto the splined hub and refit the circlip to keep in place. As it cools and shrinks onto the hub it stays put. You can just hear the lip of the fibre thrower ring rubbing slightly against the final drive casing recess as the wheel is turned by hand, so presumably that will now prevent the rock salt getting in past the flange unlike the previous design.
A new set of five brake disk mounting screws / bolts costs £4 inc VAT (and they are supplied with a dry film of loctite pre-applied) so not worth re-using the old screws 😉
Hope this helps anyone else with the same problem.