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Shopping models with or without servo assist

Bill Montgomery

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Bill Montgomery

My current bike is a '97 R1100RT. I'm considering the step up to a R1200RT. Question: what to make of the servo assisted braking system? My budget would much prefer an 05 or 06 model, but I'm real skeptical about the servo assisted braking. I wondering if I should save my pennies awhile longer in order to afford an 07 or newer model without the servo?



Bill Montgomery

Stanville, KY

'97 R1100RT

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I have both; an 05 (for sale), and an 09. While I don't know why BMW decided to build and install the servo assist in the first place, it has been no problem on my 05. I've had it serviced regularly, to prevent any mischief, and it's worked just fine, with no problems at all.


Interestingly, the amount of effort to stop is, IMO, essentially equal; the 09 takes no more lever effort than the 05. I like the fact that the brakes work with or without the bike running on the 09, while on the 05, they work but with much more effort when the motor is not running (similar to a car with power brakes).


Another potential down side to the 05 is if the servo goes bad, it's very expensive to replace it. So, there's no worry of that on the 09 bike.


Just my two cents worth. I'm sure others will give more technical information...

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I've had both. I would go with non-servo...more of a natural feel, less complicated to service and the people who know it best, BMW, decided to do exactly that -- go without servo -- in 2007. They know best - right?

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I currently have both 04 & 09 RT.


On the 04 I've had servo failure & i can confirm they are not cheap to fix. Whilst I'm not anticipating another failure it does remain fixed in your mind that the possibility remains.I don't believe failures of these servos are common but they do happen. And to make matters worse the units are not repairable.


If you can step up I would go non-servo & completely eliminate the potential of a servo failing.




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Save yourself the worry and expense. As the bike gets older you will surly run into $2500 plus bills for that servo system. Don't buy one. There is a reason they are cheaper. beech

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According to the service department of the dealer in Albuquerque the servo brakes are trouble free, if serviced which is a fluid change, in New Mexico and other low humidity states. They are more of an issue in high humidity and coastal states. The failures are usually caused by water contamination in the brake fluid. True or false, who knows? I asked about this when buying an 06 RT from a private party. It was cheap enough that I could add an extended warranty and still have less invested than the low blue book price. I found the brake service to be simpler to perform than changing the brake fluid on my ABS GL1800.

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Bike brake systems are a matter of doing decent maintenance and because that costs $ and many owners don't ride that much, brakes on a used bike might well have been neglected. Its the time that fluid is sitting in the system that is the issue- factory says 2 year changes but many experienced riders do it every year.

Despite the common belief that brake boiling fluid point deteriorates rapidly in humid climates, this is untrue - I've got the tools for measuring boiling point and have done enough measurements (mostly in NC) to know this from my own data- even 4 yr old discolored junk is not far off the dry bp of new fluid. (The wet boiling points published are obtained from what is essentially equilibrium after exposure to a water-saturated atmosphere- that's not at all like the sealed reservoir (with its internal rubber gasket) of your bike which is why real world data doesn't match the "worst case" wet bp specs.

However, DOT 3, 4, and 5.1 fluids are very sensitive to oxygen and many of the best brands are packaged either in plastic with nitrogen gas in the headspace or in metal cans precisely to keep oxygen out. It is oxygen that darkens the fluid, eats up the anti-corrosion additives in the fluid and causes the fine particulates you can find in the bottom of the reservoir. Oxidation is also responsible for the clogging gums that can form (especially in older DOT 3 types).


So if you buy any used bike, written evidence of brake services would be good to see and reduces the chance but does not guarantee no failure.


Were it me, I would spend more for a non-whizzy bike simply to reduce potential failure points and maintenance work. That's the same reason I own an 08 RT rather than a K bike- simpler to maintain and less to break. Of course, there is always the chance of getting an 07 or later the quickly develops some sort of expensive problem with ABS, the FD, or clutch just as a new bike could have problems. Its about the odds....

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Again, if BMW decided to quit making it for the R bike, I'd think twice before buying one with it. May be they know something about that system that led them to quit using it. Just another one of those BETA testing applications that didn't make the grade...apparently.

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Morning Motodan


The older power assist BMW I-ABS systems were state of the art when released for production. The older ABS-2 systems were just too slow to get the ABS response times needed for single track vehicle use and maintain short stopping distances. The ABS-2 systems were really lacking on rough roads or crosswise tar snakes (slow response times and slow reapply due to piston stroke movement).

BMW needed the make-up pump and pump pressure to obtain the brake re-apply rates to get decent rough road stopping distances. At the time piston type ABS systems were in common usage and valve systems were not fully developed yet. Don’t forget that BMW would have needed to have the I-ABS systems in use and continuous durability testing a couple of years prior to production release.

The later valve/accumulator systems were not fully developed yet.


The I-ABS system has (and still has) a lot going for it in quick response wheel brake control, learnable brake apply management, quick apply pressure build rates, short stroke lever to full pressure, etc. It’s main problem is the need for pump-run for normal braking and the lack of an accumulator in case of pump failure. The accumulator is the sticking point as the older I-ABS system uses a constant pressure/flow bleed-off that gets trapped for brake assist. Not a good system to have accumulation back up. If the I-ABS system had a means for accumulation or a back up secondary pump there would be no major complaints about the system.


With the advent of the later valve type ABS controllers with internal accumulation BMW found a lighter, less power consuming, fast re-apply rate ABS system that also lent itself to including traction control.


Even the current new generation ABS system is getting long in the tooth as newer systems now have lean angle sensors that are being used for lean angle braking modulation and faster recovery rates including multi settings for different riding conditions or riding styles or track usage.


I remember when signal plane drum brakes were state-of-the-art—Time marches on. Won’t be long before all the hydraulics are gone and brakes as all electrical/electronic with each wheel reporting to all the on board computers via can-bus.


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Thanks for the tech perspective.


I always thought of it as being something between me and the actual "braking feel" I'd become familiar with over all the years. I didn't realize the lack of linear feel and banging of my passenger's helmet on mine was just a way of making me safer.


I do appreciate your insight...at least now I don't think they were totally crazy for creating it.

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I had some problem adapting to the servo brakes after switching from 30-year-old-mushy Honda brakes but have since "found my groove" with them and have no issues using them smoothly. I've only had one day's worth of experience on an '07 RT and that was almost two years ago but I can say with certainty that the servo brakes will stop the bike VERY quickly when the need arises.

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Morning Motodan



before all the hydraulics are gone and brakes as all electrical/electronic with each wheel reporting to all the on board computers via can-bus.


Please tell me that the brake electronics are not going to be made be the same guys that make the fuel pump control modules!

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Add me to the list of owners with servo brakes, no problems with the servo system closing in on 60,000 miles. I never give the servo "feel" a thought.


I don't really see the need for them, but as I said, they've been no problem. I've serviced mine every two years, sort of.

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Weii Bill, I can tell you I really like the brakes on my 06 R1200RT.


Only problem I've had was cleaning the inside of my glasses. When I first started using them, under hard braking my eyeballs used to pop out and hit the insides of my glasses. :D (they really work)


Flushing the fluid can be a bit more of a pain. All and all I really like my brakes! One way or another if they have been properly maintained I don't think it's a big deal.


Good Hunting to you!



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Mine is an 05 with ~42K miles , no problem with the servo brakes.

I really like the two finger breaking at just about any time.

That is two fingers to actuate front and rear at the same time. What else can you ask for?

As far as the "don't buy it because more things can go wrong" is non sense.

We should then all ride carburated bikes with mechanical ignition system, with no CDI or ECU.

Also for get the new k1600 if "things can go wrong with" is your motto.


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I have an '07 R12RT without servo brakes. On a trip I rented an '06 with servo brakes that had not been very well maintained. In a parking lot I had to grab a handful of brakes and the next thing I knew I was on my side with the bike on me. I had a badly bruised knee which was sore for the rest of the trip. Personally, I would not buy a bike with servo brakes because of this but also because of the extra maintenance and the cost if the servo unit goes south. I've never had a problem with the brakes on my '07. By now the '07's are about the same price as the '06's.



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Soo . . your point is that you were new to servo brakes and grabbed a handful in a parking lot and dumped the bike . . therefore, servo brakes must be evil. Like anything new, one must acclimate themselves to things that are different. Sorry about your experience, but that hardly makes a case against the brakes. Just sayin'

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'05 with 42K, no problemes. In fact I like the servo brakes, I just grab the front brake and never touch the rear brake pedal. Works for me. I bleed the brakes every 2 years.

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After owing 20+ bikes with normal brakes including another RT, I acquired an '06 RT with servo brakes. Although it's the answer to a question nobody asked, I've become acustomed to this system, the bike is now at 112k miles, and it works fine.


Interestingly, getting on a bike with normal brakes is not a problem, and jumping back on the RT is no issue either.


It's a bit like the turn signsl cancellation issue... takes some time to get accustomed.

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My 'o4 GS had the buzzy brakes, bled them yearly as I had servo failure fear ($2k++) It was a time consuming job. The fluid, even after only a year, looked like crap.

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I love the brakes on my '05 RT, very powerful, easy to modulate and 100% reliable so far. I am aware of no failures of this system on bikes whose fluid is flushed every 2 years, though I am sure there are one or two exceptions.



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Have a 08 r1200rtse without the servo assist and find the brakes to be excellent ! Would be more concerned about the servo assist as to the added electronics . Seemed BMW were too as they decided to do away with it !

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