servo-assisted brakes in curves

[christianf]

I heard that front breaking in curves brings the bike back straight which can be dangerous since it will tend to direct the trajectory out of the curve, even if using only the rear break since the servo assisted break will engage the front break, would it not be a good idea to disconnect this item?. Is this possible and what are the issues with doing this?

[lkraus]

.

 

[fatbob]

I’ve been riding 1150 RT’s since 2004.  Over 120,000 miles, many of which on twisty roads.  I’ve never experienced what you describe.   BTW I only use the front brake lever on pavement.   

[FlyingFinn]

There are two things, servo assisted brakes, and linked brakes.

What you asked about has more to do with linked brakes than with the servo assist.

 

MANY bikes have linked brakes, meaning that applying only front or rear brakes, also causes the opposite brakes to get activated by a varying amount.

and in most implementations, the end result is very balanced application of brakes.

 

The servo assist is much less common. And I agree with many, saying that it bit of solution looking for a problem.

The only issue I had with the servo assist was that it made it more difficult to just slightly drag the rear brake when doing a full-lock right U-turn. 
That, and the added to the complexity of servicing the brakes. 

[christianf]

Thank you for the distinction. It makes sense and I will have to check the manual

1150RT ‘04. I am not sure if the ratio of assist. 

I use the front break to stop or slow down before a curve if I want to stay safe. 

[dirtrider]

8 hours ago, christianf said:

I heard that front breaking in curves brings the bike back straight which can be dangerous since it will tend to direct the trajectory out of the curve, even if using only the rear break since the servo assisted break will engage the front break, would it not be a good idea to disconnect this item?. Is this possible and what are the issues with doing this?

 

Morning christianf

 

What BMW motorcycle are you working with?  Not all BMW 1150, or early 1200 I-ABS brakes are FULLY linked. Standard 1150RT ( I-ABS )  bikes do have fully linked brakes.  (added:)  I see you have an 04 1150RT, that bike has the later I-ABS system that has the larger rear master cylinder piston & power-saver rear servo so is a better braking system than the early I-ABS systems were.

 

If you have a standard (non-RT-P 1150RT then your brakes are both power assist (servo powered) & are fully linked with both the front brake  lever and/or the rear brake pedal applying both front & rear brakes.

 

The actual braking bias (how much front vs how much rear)  is computer controlled  by the ABS module and that computer control is based on learning from past braking events vs wheel spin-down speeds. (basically the BMW I-ABS system computer tries to keep the braking balanced during normal & heavy braking by continually adjusting ft/rear braking bias ). 

 

The actual ft/rear  linking is done internal to the ABS module with specially drilled cross-over passages so no easy way to defeat the linking.

 

You can install an 1150 RT-P (police bike) I-ABS module as those are linked front to rear but not rear to front so they have both front & rear linked  brakes from the front lever but still have stand alone rear braking from the rear brake pedal.

 

Or, you can totally remove the ABS system then have very nice standard braking front  brake from the front lever & standard rear braking from the rear pedal but will then have NO ABS.  You will then  have to work with the brake light & tail light wiring by adding a relay to control the brake lights form your current reverse logic  brake light switches (or install non ABS normal logic brake light switches).

 

 

 

 

 

 

 

 

 

 

[Shane J.]

10 hours ago, christianf said:

Thank you for the distinction. It makes sense and I will have to check the manual

1150RT ‘04. I am not sure if the ratio of assist. 

I use the front break to stop or slow down before a curve if I want to stay safe. 

I would suggest you research trail braking, properly used you will avoid the situation of mid-curve braking problems.

[Rider1260]

I have ridden your model and my 08 RT has linked brakes I have not noticed any tendency for these bikes to "stand up " with mid corner breaking now my old Yahama fj1200 with the 16" wheels that was a different thing , but easily corrected with countersteering and body position. 

The biggest change for me is how flat these bikes stay when on the breaks ( little or no ) fork dive so I'm not unloading the rear wheel like you do on a sport bike. 

[christianf]

@dirtrider i an trying to understand this information. The changes that you suggest are beyond me. I don’t think I will get myself involved with that at this point. Better to stay safe with what I have. Thank you for your detailed explaining. Be well

 

[AviP]

I have a R1100RT that does not have this feature which was added to the R1150RT. The geometry on both bikes is pretty similar and having braked quite aggressively in the curves, I can assure you that linked brakes will not make your R1150RT straight line the curve. Now try the same thing on my Kawasaki ZX11 (now sold) and it will instantly want to go straight. Just mentioning the ZX11 since I think I know what you are talking about.

 

The best thing you can do is practice in a controlled environment to build confidence in your bike.

[christianf]

Practice, Practice,Practice,

[RPG]

As an '04 RT owner, I just had to learn not to stab the rear brakes in low speed parking lot situations.

 

Other than that little idiosyncrasy, I think the stock I-ABS works marvelously and I've zero issues with mine in 110,000 miles.

 

Personally, I wouldn't want to take out the ABS. It arguably probably saved my life in my last deer crash.

 

RPG

[tallman]

400,000+ miles on every type of BMW made before 2013.

 

My .02.

These bikes are overdesigned, with quirks.

For most situations, the bike can outperform the rider..

 

Practice, straight line braking, from increasing speeds.

Dry.

Then repeat with wet pavement.

 I've had to use brakes in situations where the system performed flawlessly and trucks, trailers, deer, etc.

were handled in emergency situations. (examples: deer leaping from woods right in front, truck trailer in the dark with no lights, etc.)

 

BITD. David Baker to his R1200 GS to the track and provided detailed reports.

Many others have done this also.

Not one instance can I recall of extreme braking, under the conditions you outline, reported as the cause of a problem.

 

I've had to use the anti-lock features, in the rain, dark, 2up, fully loaded when idiodrivers ran lights etc.

Not a removal advocate.

Best wishes.

[cat0020]

 

I'm used to & prefer motorcycles without ABS, over 750k miles legged over two decades on over 40 different motorcycles. 

I'm on my second Oilhead with servo-assist ABS, in the process of deleting the servo & linked-ABS system, lose a few pounds near the top of the bike.

Reduce unnecessary battery drain while stopped at traffic lights and make less abrupt braking. 

IMO, brakes, who needs them; they only slow you down and limit your options in avoiding impact. 

 

 

[Sam Taylor]

I've eliminated the ABS on my early 02 1150RT, due to the system's demise.

 

The brakes without the ABS are superb, yes, but I am not so old or so bold as to know that it's better to have (good, working) ABS than not.

 

But now we're in oil thread territory so I'll just pass this on:

 

I'm pretty sure the reason my ABS packed it in was my brake hoses sloughed off internally and damaged the expensive ABS unit.  I could blame BMW for fitting some of their crappy rubber hoses but the truth is I should have swapped out those hoses years earlier for some Spieglers.  Which I have now done after the horses left the barn.

 

Another lesson learned.

[christianf]

All good, trAilbreaking works great. 

[AndyS]

On 4/6/2020 at 3:33 AM, christianf said:

I heard that front breaking in curves brings the bike back straight which can be dangerous since it will tend to direct the trajectory out of the curve, even if using only the rear break since the servo assisted break will engage the front break, would it not be a good idea to disconnect this item?. Is this possible and what are the issues with doing this?

 

You are looking for a problem that just doesn't exist on these bikes.

The system works fine.

I however had a servo failure, so I (like so many others) have removed the system. The brake feel is now great (particularly at walking speed). Otherwise, as I say, you are looking to fix a problem that doesn't exist.

[Rinkydink]

The first thing I learned on my 04RT was to not kill the motor early while arriving on my steep downhill driveway. I almost had to buy a new garage door AND a new seat. 

[AndyS]

3 hours ago, Rinkydink said:

The first thing I learned on my 04RT was to not kill the motor early while arriving on my steep downhill driveway. I almost had to buy a new garage door AND a new seat. 

 

 

 

True dat