ABS woes

I have a bike with ABS and linked brakes (BMW R1150 RT). From what I have
been told and have verified, my stopping distance is the same if I apply
only front brake, only rear brake or both together. What I am not sure about
is how the ABS system works when both brakes are applied.

Yesterday I was going down the back of Mt Glorious and using fairly stiff
braking when the ABS started to cut in. Now on a dry downhill stop I could
imagine the rear brake locking but with so much weight on the front I could
not imagine the front wanting to lock. Now I could not be sure if the ABS
was cycling only the back wheel or if it was cycling front and back but it
was a bit disconcerting at the time. Also being linked even if I back off on
the foot brake it would make no difference.

Any comments or help (other than buying another bike)

 

The problem isn't the ABS it is the silly linked braking system.

See if you can get someone to delink the hydraulics and enjoy the
improvement in feel instantly


G-S

 

Don't listen to G-S. He replies negatively to every post about linked
brakes but never elaborates with any basis of substance for his bias.
He probably got beaten at a trackday by a bike with linked brakes. He
doesn't even realise the brakes on your bike are not feasibly
delinkable.

Both your brakes are linked to a single hydraulic control unit with
ABS, which seems, as you state above, will apply the same amount of
braking force whether one or both of the brakes are applied
(presumably if you apply more force on one than the other then the
greater braking force will be actuated on both wheels), but not
necessarily evenly, the force will vary according to a controller
which 'learns' what bias is required based on the way the bike is
loaded. It seems that the ABS is connected to the integral controller
so if one wheel locks, it will release both wheels. Maybe it's time
to read the chapter on how to brake in the owners manual? Did you by
any chance start the bike with the brakes applied prior to your trip
down Mt Glorious ?

Nev..
'07 XB12X

 

It's very common to de-link brakes on various models. I haven't read of
anyone doing it with that particular model but I *strongly* doubt it's
impossible. It might require new calipers and lines but that's all off
the shelf stuff.

As for replying this way about linked brakes I do so because they are a
bad engineering concept


G-S

 

But it works just fine in my cars..

 

Get back to me in 20 or 30 years when they finish designing one that
does then


G-S

 

True... but cars don't lean (well not most of them anyway!).


G-S

 

Come for a blast in the roadster
it leans

 

I quite like the linked brakes on my super blackbird. Never had a problem with
them and to be honest they seem to stop me better. I still have the option of
using just the rear to settle the bum down in hard cornering so to me it is the
best of both worlds.

Fraser

 

I don't have a problem with linked brakes per se. My previous ride was a
Guzzi Cali which had the rear disc and a front disc on the pedal and the
other front disc on the lever and I didn't have a problem with that. But
the BM (and I believe only on the RT) the system is set up so you get all
brakes whether you push the pedal or pull the lever. That being said with
the telelever front suspension I don't get much dive and I find I can use
the 'back' brake coming into a corner.

My main concern still is that if the ABS cuts in early on the rear wheel
(downhill, no pax or luggage) is the ABS releasing the front brake as well ?

May be I'll just have to go and find a steep hill somewhere and find out
what the story is.

 

Or read the owners manual?

Boxer

 

The Owners Manual gives a good general description of the system, but not
so informative when it comes down to specifics like I want.

Don

 

We're not talking about various models. We're talking about a
particular BMW model which has integral linked brakes with ABS.

Why?

Nev..
'07 XB12X

 

I'm 90% sure that my 1100GS did release the front brake when I locked the
back brake on gravel but I just can't remember clearly enough. (I know it
certainly released the back brake (and my sphincter) as I went sailing off
past the turn-off I was supposed to take!!)

Easy test; find some gravel or a dirt driveway and have a stomp on the
pedal..

 

Regardless how many owners of bikes with linked brakes tell G-S that he
is wrong, he refuses to accept the fact. Not riding a bike with linked
brakes somehow makes him more of an expert on the matter than those who
do. *boggle*

Nev..
'07 XB12X

 

Don & Cheryle Smith wrote:

That is what I believe it will do.

This is the reported behaviour of "sportier" motorcycles fitted with the
same ABS controller.

A tank bag with much weight on it, very spirited riding, and you _might_
get it near enough to a stoppie for the ABS to release the front brake.

regards,
CrazyCam

 

And why should not the general principle that unlinked brakes > linked
brakes (other things being equal) not apply to this model in particular?

Because it replaces user control of braking with semi-automatic control
by the bike, and leaves the rider with access to only a subset of those
braking behaviours that a non linked braking system can generate.

It's the same mindset that says 'traction control is good because people
can't be trusted to manage loss of traction'.

Me? I bought a 180kw front wheel drive car and chose to have traction
control fitted even though it was a zero cost option.

Result? The car is more *fun* to drive.

Nev... honestly I don't mind if people want linked brakes. And if they
are riding something like a GoldWing that weighs 350kg and will never be
punted hard then it won't make a practical difference.

On a bike that will be punted hard it can (depending upon the riding
style of the rider).


G-S

 

How many race bikes are fitted with linked brakes Nev?

Doesn't that say something about the ultimate performance limits of
linked brakes being less than that of unlinked brakes?


G-S

 

In aus.motorcycles on Fri, 07 Mar 2008 22:34:37 +1100

Explain the difference in intended use of a race bike and a road bike,
paying particular attention to the expected use of the braking
apparatus of both machines.

Zebee

 

The expected use of track bike is riding at 110% where the ultimate in
performance is the highest priority (so as to beat the other racers).

The expected use of most road bikes is riding at 110% where the ultimate
in performance is the highest priority (so as to beat your mates)

The braking appatatus of both machines are expected to be used to the
absolute limit and suffer from occasional over heating and regular fade.


G-S