Need Advice On K1200rs Rear Brake Problem!! - K-Bikes.com - Excellence in Motion
 
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post #1 of 8 (permalink) Old Jul 12th, 2008, 4:34 pm Thread Starter
 
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Need Advice On K1200rs Rear Brake Problem!!

HELP!!! I have a 1999 K1200RS and the dealer said the rear rotor was warped. I checked it at home while it was on the bike with a dial indicator and it showed about .020 out. Next I bought a complete new BMW rotor and put on... STILL out!!! I took BOTH rotors and checked them off the bike for runout and they BOTH checked out true. Put the new one on, bolted and torqued up, and is still out! Is there something in the drive that is not sitting square? The bike had 17K miles on it when I bought it and I had it serviced at 18K. Any suggestions???
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post #2 of 8 (permalink) Old Jul 12th, 2008, 11:37 pm
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well I would set up the ind. on the face of the crown wheel and see if I still have that .020 runout....

if so then you know ya gotta dig deeper, outboard bearing is prone to failure, BMW gets about $120 for the bearing, its a BMW specific part and bearing suppliers will not have them in stock or priced lower.

old ones had 19 balls in the cage, newer (better) bearing is 17 balls.

not a job for the 'mechanically declined'

Mike Kelly

Triple M Engineering

K12RS

Stanley, NC
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post #3 of 8 (permalink) Old Jul 13th, 2008, 5:27 am
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Interesting question. As MikeK suggested you might have the RD bearing worn, but see first if you can feel any play at the wheel?

A few tests might turn up something. The were some reports a while back of people replacing rotors with oem and getting runout. You could first check your new rotor on a surface plate or plate glass with some blue to make sure it's not warped.

Have you first checked what your ABS rotor to sensor clearance is doing? Measure with feelers at 3 equidistant points of wheel rotation bike on and off center stand. Compare results.

It's not guaranteed to work but here's a couple of ideas: First mark on the rotor where max runout occurs. Then check at the wheel rim, remove wheel and rotate a stud at a time. If the wheel is true (unlikely) your 20 thou comes out as 30 thou at the rim. As you move the wheel around, If the position of max runout on the rim moves, then that suggests it's an error in the rim to be ignored. If however max runout stays at the same position, relative to the frame, then that suggests the axle bearing. You could take this a step further by rotating the rotor to different positions to- changing max runout position likely to be the rotor or it's not seating properly on the flange. It's easy to get some dirt behind.

I tried measuring runout on my front rotors. It's not that easy, particularly as the front rotors have holes in them. The real test is also if you feel it during braking?

If you remove the ABS ring and rotor you can get a dial gauge on the face or edge of the mounting hub just forward of the seal without dismantling further. Fit a temporary long piece of flat steel with a couple of holes picking up 2 wheel studs. Heave on the bar whilst watching the dial gauge. If you get big changes look at bearings. If there is a fixed runout that doesn't change position when you heave - that's real bad news.

Your dealer won't be diving in there with dial gauges - they probably felt pulsating braking on the rear. If you guys have brake test machines, they can tell this by slowly applying a brake and watching for the fluctuations in braking measured on their roller wheel. Make sure you have a set of decent pads in there and check ALL pistons are free and move easily. They can seize or stick on older bikes.



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Last edited by voxmagna; Jul 13th, 2008 at 5:37 am.
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post #4 of 8 (permalink) Old Jul 13th, 2008, 6:55 am
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make sure you torq them in stages and pattern...and that the bosses are clean
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post #5 of 8 (permalink) Old Jul 13th, 2008, 7:59 am Thread Starter
 
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Thanks for all of the suggestions! Later this afternoon I'll dive back into it. Here's what I did already: Made sure the mating surfaces were clean (there was buildup under/around the old rotor/drive), torqued -2- screws for rotor to 21nm evenly, torqued caliper to 40nm evenly and set ABS sensor at .50mm, torqued wheel bolts to 105nm evenly. The pads are brand new on the caliper. The rear brakes have always seemed to make a chunk chunk pulsating noise when braking since I bought the bike with 17K miles on it. I mounted my mag base on the paralever arm and set the dial indicator on the rotor just outside of the last set of drilled holes for my reading. BOTH rotors showed out the same amount in the same spot when mounted... that's when I took them both and checked runout on the rotors. Both rotors showed perfect when off the bike. (Looks like I'm going to have a spare complete used BMW rotor assy for sale!). I couldn't get a very good reading on the crown wheel, but it appeared to have one area at about .004 My friend suggested that perhaps the bearing inside was not fully seated. Also, I don't think it would show .020 runout on the crown wheel, the further out the runout is checked the greater the runout, correct? I do have mechanical aptitude, just don't want to start tearing into the drive and replacing parts without knowing what's causing my problem. If I have too, I would apprieciate any helpfull hints. Oh, and YES I do have a BMW service manual on CD. I'll post my findings later... Thanks again!
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post #6 of 8 (permalink) Old Jul 14th, 2008, 3:45 am
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Sounds like you are doing the right things. Checking the runouts for change with wheel on/off the ground and some weight on the pillion should confirm if it's a bearing issue.

Looking at the relative radii of the crown flange and rotor I'd estimate your 20thou corresponds to about 5 thou at the flange. I never found runout measurements that precise and repeatable on the bike, but the calculation is a bit close to your 4 thou figure.

I kind of alluded to it, but the only thing I thought could put out the crown flange is a very nasty whack hitting the rear wheel. Pulling the RD apart is a real nightmare even with experience. If you have to do it just for your own conscience, you can probably put the crown between centers and re-check runout on the flange. I managed to pick up a Boneyard RD complete for about $100. Cheap insurance and something worth thinking about before going where few have gone before.

Good Luck, keep us posted.



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post #7 of 8 (permalink) Old Jul 14th, 2008, 11:41 pm
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just scanning down thru this again.... run-out at the crown wheel would translate not only to the brake rotor but also to the rear wheel wouldn't it?

I'm guessing that a guy with the wherewithall to set up dial indicator on the rotors and crown wheel would have noticed any massive rear wheel runout.

still both rotors showing the same runout at the same spot when mounted is telling us that it not the rotors.....keep digging, something simple/goofy will turn up.

Mike Kelly

Triple M Engineering

K12RS

Stanley, NC
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post #8 of 8 (permalink) Old Jul 15th, 2008, 2:29 am
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With that much run out at the rotor would be amplifide gratly at the tire...would think that would be to the point that the tire would rub on the swing arm in that spot?....not only that but should be felt by just rolling along....IF...it were a bearing problem..I would place the dial on the swing arm and check run out...mounting the dial on the frame or free standing fixed to anything but the swing arm would also pick up an off tracked swing arm and might not be the bearing at all or the rotor but the swing arm itself..I think..just woke up........DOH..nother day
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