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Discussion starter · #21 ·
OK...I'm not asking to re-invent the wheel. I have the bike at a dealer, albiet not a BMW dealer because of where I live. The suggestions in this forum were given to him. I was hoping that a BMW owner would have experienced the same problem at some point and offered the obvious solution. The wheel is true as is the rotor as initially stat :dance: ed. I am aware that others have posted questions about the similar problem and don't want to start a 'knowledge war'. Thanks so much for all of the input. When I solve the problem, I will re-post.
 
You talk about pulsing. Is the ABS unit kicking in even on light braking? Like someone said pull the relay for it and then you will know for sure.

Could it be one of the brake calipers is frozen and you then get uneven braking pressure and binding?

Being you have a 2000 I believe the front brakes have 2 cups per side. Are they put back in right and both moving freely.

Let us know what you find.
 
deanwoolsey said:
I'll bite.

Ron, if a rotor cannot warp answer me this. When I take one to the auto parts store and have it "turned" or "cut" and the machine takes a smaller amount off part of the disc than it does off the other doesn't that mean that it's not symmetric? If it's not symmetric then isn't it warped? Have you never seen lateral run-out on a rotor sometimes caused by a bad hub? If I understand your position correctly you are saying that basically the rotor has more drag on one part of the rotor than the other. I do not believe this could physically cause the brake lever to push back out which is obviously due to hydraulic pressure, yes? Now granted, inconsistent drag or coefficient of friction on the rotor would cause pulsing in the vehicle but it would transfer into the tires and you would feel it in the entire vehicle, not the brake lever. While I don't doubt your scientific data, I do doubt it's interpretation. Then again, I've been wrong before.
Here's some excellent reading to describe what is going on.

It's the most concise "laymans" description I've ever come across. There are volumes of published SAE papers (that go into extreme minutiae and are excellent bed time reading since they are guaranteed to put you to sleep) and come to the same conclusion:

The "warped" brake disc myth

Correct pad and rotor bed in
 
peair said:
OK...I'm not asking to re-invent the wheel. I have the bike at a dealer, albiet not a BMW dealer because of where I live. The suggestions in this forum were given to him. I was hoping that a BMW owner would have experienced the same problem at some point and offered the obvious solution. The wheel is true as is the rotor as initially stat :dance: ed. I am aware that others have posted questions about the similar problem and don't want to start a 'knowledge war'. Thanks so much for all of the input. When I solve the problem, I will re-post.
There is no knowledge war. This is about getting your issue fixed. If you believe the mechanic where you've taken your bike, fine.

In my experience about 1 out of 100 are not knowledgeable about ANY issue, the other 99 will either completely bs you, make wild guesses or parrot what they've heard from other "expurts" that went before them. Most of these guys didn't even graduate high school...

Ask him if he believes if rotors can warp. If he does you need to find another mechanic.

Simple. :check:
 
Ron, I don't think our positions really conflict. The author does cover both of our positions in his writing. As usual you have valid points, but it is possible for a rotor to warp (lateral runout) as the author indicates. I would grant you that the majority of the time the symptoms are likely caused by what you describe. To tell the truth, I never even considered measuring the thickness for variation as every issue I have ever seen was with lateral runout. That's always been my interpretation of warpage. I have never personally seen lateral runout on any of my motorcycles. Thanks for the new perspective.
 
JPSpen said:
You've either got a warped rotor or a bent wheel...Only thing that will make the brakes pulse..

It's most likely a warped rotor...... You should be able to put the bike on the center stand. Spin the wheel and figure out which it is right quick...If it's as bad as you describe it shouldn't take a rocket scientist or a dial guage to figure it out.. One of the calipers may actually move around...Just spin the wheel and very gently apply the brakes..Just enough to make them drag. It should be as obvious as the nose on your face...


Sorry you're having problems... Got to be a rotor...The ABS is pretty harsh so I think You'd know it if it was the ABS..After re-reading your post I guess the ABS could be a possibility... Definately disable it temporarily to check ....1/2" of movement in the lever is severe at best...And you'd hear the ABS pump doing it's thing if it was the ABS...Might listen for that...

Good Luck

John

John
There is a 3rd possibility and it is actually the most common - uneven buildup of pad material on the rotor. Sometimes this can be cured by several hard stops to really heat up the rotors and then let them cool without using the brakes.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Matt
 
Ye gods I almost got a headache reading all the posts! As an ASE master tech for over 25 years I have seen many odd things involving anything with a motor that moves. I have pictures of vented brake rotors which have worn down to the point of only one thin slice of metal is left, razor sharp. We use the term 'warped rotors' because MOST of the public is not really up on studying brake issues, they simply want the dang thing fixed. Much like the term "tune-up" it is misunderstood and misused. When I hear 'tune-up" along with "check engine light" I know I have some explaining to do. My favorite customers? Bike riders!! Go figure.... :D
 
RonKMiller said:
There is no knowledge war. This is about getting your issue fixed. If you believe the mechanic where you've taken your bike, fine.

In my experience about 1 out of 100 are not knowledgeable about ANY issue, the other 99 will either completely bs you, make wild guesses or parrot what they've heard from other "expurts" that went before them. Most of these guys didn't even graduate high school...

Ask him if he believes if rotors can warp. If he does you need to find another mechanic.

Simple. :check:
ron
although i refuse to get involved in your rotor theory i do take offense to your comment about mechanics.... most if not all of us ARE knowledgeable on many issues. in the areas we are not knowledgeable in we can usually figure it out. please do not confuse mechanics with the latest generation of "technicians". as vehicles become more and more electronic and the desire to r&r instead of repair the need for a real "mechanic" becomes less and less.
ya i did graduate from high school.
oh you misspelled experts
thanks, john
 
Hi there!!!!
I am new in this forum, and I am writing from Venezuela, excuse my bad english.
I got the same problem of pulsing front brakes, so I was seeking the cause, and put my bike (K1200LT 2007) on her center stand and was checking the pads and calypers for any leaks.
I tried to lift up the front wheel by pushing a little the headligth up, and for my surprise all the front wheel came down. Thats when I realized too see that the Ball Joint in the LOWER FORK BRIDGE is complete broken and loose free, thats why when I used the front brakes, all the front wheel shaked like if it were pulsing brakes.
Take a look on your ball joint if it is loose or broken, maybe it is the worm that are you making nuts.


Best regards,

Anton Danzer
Maracay, Venezuela.
 
drjohn55 said:
ron
although i refuse to get involved in your rotor theory i do take offense to your comment about mechanics.... most if not all of us ARE knowledgeable on many issues. in the areas we are not knowledgeable in we can usually figure it out. please do not confuse mechanics with the latest generation of "technicians". as vehicles become more and more electronic and the desire to r&r instead of repair the need for a real "mechanic" becomes less and less.
ya i did graduate from high school.
oh you misspelled experts
thanks, john
It's not a "theory" like some dark matter blathering from Steven Hawking.

It is a well documented fact backed up by MANY, many technical articles published by SAE . - you know who they are, right? I'm a member, are you?

Well, I certainly agree with you about the new breed of "Technicians" and apologize profusely for lumping true mechanics in with them. I should have used the term technician in the first place. My bad.

I salute anyone that calls themselves a mechanic :thumb: - since mechanics actually figure out why it's broken and know how to fix it! ..and if they don't know right off the bat they can usually figure it out. They also know how to fix it without first throwing a bunch of expensive parts at the problem. :yeah:

It's kind of like the great Julia Childs. Everyone referred to her as a chef - and she despised the title. She preferred to be called a cook, since that's what she really did. And man, could she cook: MORE BUTTER! ;)

My big issue is that the "art" of knowing how to actually fix things is being phased out of every aspect of our industrial society. "Just buy a new one or replace it" is how most problems are handled. Major corporations find it is easier and more expedient to buy failure prone products from China then to actually figure out how to improve the quality of their products. ...and boy howdy, is it EVER showing: Just this morning BMW cars announced a recall of 241,000 vehicles for a tail light issue. How hard is it for the Ultimate Driving Experience to engineer a tail light that works as expected?

BMW recalls 241,000 3-Series models over taillight failure

The GREAT news about all this is that there is a tremendous demand for well trained and experienced mechanics. You sir, obviously, are the exception to the vast majority and will have job security forever!

By the way, I misspelled expurts on purpose and put quotation marks around it. It's a play on words, kind of an extended metaphor. Never mind. :rolleyes:

When I graduated from high school they taught me to start sentences with capital letters. Touche. :D
 
My new to me 2000 K1200LT came with pulsing front brakes - seems both previous owners used the brakes very lightly, last owner said he used front brake lightly not a fast driver, I've used the brakes my normal way and pulsing is slowly fading after 200 kilometers and some 130 kph HWY use, I also get a hissing sound from one of them I can only hear when wearing a 3/4 helmet - seems there was something deposited irregularly on one or both disks which is being removed by more vigourous braking - might take some sandpaper to them this weekend
 
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