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post #1 of 10 Old Oct 31st, 2006, 3:05 pm Thread Starter
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Brake Question

When you pull on the handlebar brake does it engage both front discs or just one of them? How about the foot brake, does it enage one of the front discs and the rear?
Jim

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post #2 of 10 Old Oct 31st, 2006, 6:46 pm
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You've an '05 LT, eh?

Answer is, it depends. Mostly on how fast you're going, but also on how hard you hit the brakes.

Yes - they're 'linked'. But you'll get action outta both only if you're going fast enough and hit the brakes hard enough for the computer to figure you want some help there. What exactly those threshold levels are, I dunno. Should be good info in your owner's book - assuming you've got it.

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post #3 of 10 Old Oct 31st, 2006, 9:51 pm
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Quote:
Originally Posted by jsciullo
When you pull on the handlebar brake does it engage both front discs or just one of them? How about the foot brake, does it enage one of the front discs and the rear?
Jim
The simply answer is there is no "fixed" relationship between the front and rear brakes. The front brakes are fed by a common hose, so they operate together. The info in the first 4 pages of this article will give some background info on the system arrangement:
http://www.bmwlt.net/ubbthreads/down...ch_id=6311?Cat=

For ease of explanation: The lines from front and rear master cylinders meet at the Integral system pump unit under the rider's seat. The Integral computer next to the pump determines (based on lever actuation, speed of lever actuation, road speed at each wheel, phase of the moon, etc.) how much pressure the two pumps in the pump unit should apply to their respective front and rear brake wheel circuits. The force distribution is infinitely variable, and thus is far more flexible and adaptive to conditions than prior motorcycle systems, such as Honda's one-front-disk-one-rear-disk linked system.

In addition, as I understand it, above certain speeds, in a panic brake application the computer can actually control the pumps to apply the brakes faster and harder than you can, thereby starting the energy dissipation process sooner, and shortening stopping distance (something like a bike-length shorter from ~60 mph). There are lots of folks out there that brag that they can stop in a shorter distance than an ABS system can, but I'd pay good money to see them try to beat this rig, even under controlled conditions -- let alone in real-world traffic situations, where the so-called expert doesn't have the benefit of working their way up to a maximum-performance stop.

Mark Neblett
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post #4 of 10 Old Nov 1st, 2006, 8:46 am Thread Starter
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OK - when I hit the foot brake (rear brake)- no squeek - when I hit the hand brake (front brake) at low speeds I notice a squeek. Sounds like I need to replace the front brake pads but do I replace pads on both rotors or just one of the rotors? If its jusst one of the rotors - which one?
Jim

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post #5 of 10 Old Nov 1st, 2006, 9:20 am
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Quote:
Originally Posted by jsciullo
OK - when I hit the foot brake (rear brake)- no squeek - when I hit the hand brake (front brake) at low speeds I notice a squeek. Sounds like I need to replace the front brake pads but do I replace pads on both rotors or just one of the rotors? If its jusst one of the rotors - which one?
Jim
Always replace both!!! They should wear evenly, but if they don't you need to fin the root cause first... and then replace both sets of pads at the same time.

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post #6 of 10 Old Nov 1st, 2006, 9:42 am
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Quote:
Originally Posted by jsciullo
OK - when I hit the foot brake (rear brake)- no squeek - when I hit the hand brake (front brake) at low speeds I notice a squeek. Sounds like I need to replace the front brake pads but do I replace pads on both rotors or just one of the rotors? If its jusst one of the rotors - which one?
Jim
I would say the squeak is from the rear as at low speeds and light application you do get a little rear brake action. How many miles on the bike? I am approaching 24 K and still have lots of pad left front and rear (but that is subjective to riding style). But my rear does squeak at light application of either front or rear. Visually inspect the pads ( I do every 6K) and that will let you know when to replace, there are no audible wear indicators on these pads.

John
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post #7 of 10 Old Nov 1st, 2006, 12:55 pm
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Quote:
Originally Posted by jzeiler
I would say the squeak is from the rear as at low speeds and light application you do get a little rear brake action. How many miles on the bike? I am approaching 24 K and still have lots of pad left front and rear (but that is subjective to riding style). But my rear does squeak at light application of either front or rear. Visually inspect the pads ( I do every 6K) and that will let you know when to replace, there are no audible wear indicators on these pads.
John's right -- the squeal's at the rear. When you use the rear pedal, the brake is usually applied harder than if the rear's applied by the front lever, so the rear caliper pistons dampen out the vibration (squeal). When you use the front lever, the front brakes are applied, and depending on the degree of application, a small pressure is applied to the rear -- a pressure which is insufficient to have the rear pistons really clamp the pads against the disk, and therefore the rear pads can sing.

FWIW, I believe this is part of the problem with rear brakes squealling as much as they do. I'm guessing that those of us that use the front brake a lot are unknowingly lightly applying the rear all the time, leading to the rear pads glazing (and thus becoming more susceptable to squealling). Accordingly, I try to remember to occassionally use only the rear brake to slow from a high speed run to try to eliminate rear pad glazing. It's not a perfect cure, but it at least seems to help while we all try to come up with a final solution.

Mark Neblett
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post #8 of 10 Old Nov 2nd, 2006, 9:13 am
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Quote:
Originally Posted by mneblett
John's right -- the squeal's at the rear. When you use the rear pedal, the brake is usually applied harder than if the rear's applied by the front lever, so the rear caliper pistons dampen out the vibration (squeal). When you use the front lever, the front brakes are applied, and depending on the degree of application, a small pressure is applied to the rear -- a pressure which is insufficient to have the rear pistons really clamp the pads against the disk, and therefore the rear pads can sing.

FWIW, I believe this is part of the problem with rear brakes squealling as much as they do. I'm guessing that those of us that use the front brake a lot are unknowingly lightly applying the rear all the time, leading to the rear pads glazing (and thus becoming more susceptable to squealling). Accordingly, I try to remember to occassionally use only the rear brake to slow from a high speed run to try to eliminate rear pad glazing. It's not a perfect cure, but it at least seems to help while we all try to come up with a final solution.
Mark, I always value your opinion and technical knowledge concerning the K1200LT. However, this is one time that I wish to challenge that knowledge. If I understand your statement that "applying the front brake lightly applies the rear brake" then I must assume that one can not apply full braking to the rear by using the front brake lever. Can you direct me to any documentation that leads to that conclusion?

I am of the opinion that both brake controls do essentially the same thing. Again, I value your knowledge and opinion.

Jamie
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post #9 of 10 Old Nov 2nd, 2006, 9:34 am
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Quote:
Originally Posted by mneblett
FWIW, I believe this is part of the problem with rear brakes squealling as much as they do. I'm guessing that those of us that use the front brake a lot are unknowingly lightly applying the rear all the time, leading to the rear pads glazing (and thus becoming more susceptable to squealling). Accordingly, I try to remember to occassionally use only the rear brake to slow from a high speed run to try to eliminate rear pad glazing. It's not a perfect cure, but it at least seems to help while we all try to come up with a final solution.
I found the same thing through trial and error. I make several stops from 50-60 MPH using the brake pedal if I hear any noise from the rear brake. This seems to deglaze the rear pads and eliminates, at least for awhile, the noise coming from the rear brakes. YMMV

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post #10 of 10 Old Nov 2nd, 2006, 4:59 pm
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Quote:
Originally Posted by bikebum
If I understand your statement that "applying the front brake lightly applies the rear brake" then I must assume that one can not apply full braking to the rear by using the front brake lever.
Sorry for the confusion -- I was referring to low amounts of front brake application, this typically results in small rear application (unless the front is in ABS mode).

As a general rule, the application of *either* lever results in application of *both* brakes, per the computer's programming. The only excecption of which I'm aware on the LT is programming which allows the rear brake lever to only actuate the rear brake when at a very low speed and with very light rear pedal pressure.

As I understand the system, it has the ability to infinitely vary the distribution between front and rear, depending on need. For example, when the braking level is below ABS activation, the distribution is determined on the fly in accordance with a predetermined distribution formula, which accounts for several variables (vehicle speed, application pressure, application speed, vehicle loading, etc.). This capability is also useful above the ABS threshold; for example, if above the threshold at either wheel, the brake force can be very rapidly increased at the other wheel to help bring the locked/nearly-locked wheel back below the ABS threshold.

That clear things up, or confuse things more?

Mark Neblett
Fairfax, VA
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