Linked brake question

[MIKE R]

My 07 1200GSA has linked brakes. Use the front brake lever and both front and back brakes are applied.

Now here's my question

How much bake brake is applied?

When braking normally I often miss the back brake even though I have an extender fitted. In an emergency, OH MY GOD, braking situation if you only used the 'front' brake lever, would you get optimum braking due to the linkage?

I am asking this before I adapt something to make the foot brake easier to apply.

Thanks in advance for any info.

Mike

 

[SpyInTheCamp]

Why not practice if you are so worried? Or train yourself to be able to better use the rear...

Out of interest, what kind of boots do you use or size feet do you have?

Kai

 

[cookie]

i suspect the back brake is applied at near maximum force, just below the ABS threshold.

this would explain the ABS pulsing if the rear pedal is given any significant pressure when the front is already applied.

it would also explain the ridiculous pad & disc wear on these bikes.

 

[BBB61]

The rear pad wear on the 1200 is no worse than it was on the 1150 on the original BMW pads, in my own personal experience.

As for how much the rear brake is applied I would suspect that will depend on how much pressure is applied through the front lever rather than being applied at near maximum force every time the front lever is applied.

 

[Slartibartfast]

I haven't done a lot of miles on the GS yet but did have to "hunt" for the standard brake pedal on the demonstrator (lack of familiarity rather than a long term problem).

The bike I bought had a brake extender and it feels about right.

My limited experience feels like adding rear brake whilst using the front brake doesnt make a huge difference ... which probably means I haven't got a feel for the right amount of pressure yet. That initially led me to think the rear brake was weak ... but that clearly isn't the case now I am getting used to applying in on it's own for slow manoeuvring and pillion duties.

I'm not sure what type of extender is on my bike but I assume Touratech. It's pretty big and I would have thought making it much bigger would cause a different problem

 

[1Rider]

It all depends

Mike,

my understanding is that it all depends. Basically several situations to consider (and if you have ABS):

(1) Is the ABS turned on (Normal) or,
(2) is the ABS turned off (Manual)

(A) do you apply the hand brake handle/lever for "max" breaking
(B) you apply less...

(*) is (road/tire) friction and brake applied sufficient to "lift" the rear wheel
(**) not so...



1A* hardly...
1A** close to as much as available

1B ??????

2A* as 1A as (at least the 07GSA) the rear still is under ABS (only front manual) -
2B ?????

But you may of course manually applie the rear breake - (1) ABS functions, (2) ABS rear overridden an manual braking applies also to rear.

Rgds,

Paul

 

[cookie]

The rear pad wear on the 1200 is no worse than it was on the 1150 on the original BMW pads, in my own personal experience.

As for how much the rear brake is applied I would suspect that will depend on how much pressure is applied through the front lever rather than being applied at near maximum force every time the front lever is applied.

you don't have the 07 brakes though, or do you?

 

[cookie]

Mike,

my understanding is that it all depends. Basically several situations to consider (and if you have ABS):

(1) Is the ABS turned on (Normal) or,
(2) is the ABS turned off (Manual)

(A) do you apply the hand brake handle/lever for "max" breaking
(B) you apply less...

(*) is (road/tire) friction and brake applied sufficient to "lift" the rear wheel
(**) not so...



1A* hardly...
1A** close to as much as available

1B ??????

2A* as 1A as (at least the 07GSA) the rear still is under ABS (only front manual) -
2B ?????

But you may of course manually applie the rear breake - (1) ABS functions, (2) ABS rear overridden an manual braking applies also to rear.

Rgds,

Paul

fecking hell

 

[nedflanders]

Pressure must vary from bike to bike, my rears were down to the metal at 1600miles normal riding, and no I wasn't resting my foot on the lever (impossible anyway) and the dealer says theres nothing wrong, oh well best see what it's like in another 1600miles.

 

[MikeP]

How much bake brake is applied?

You may have to ask the "Swindon Poisoner" that!

The way I understand BMW's semi-linked system is that the force applied to the rear brake is dependant upon the effort applied to the front lever.

If you use both brake levers together, then the force the rider applies to the rear will supersede the 'link' unless it's less than the bike recognises the hand lever is being applied.

In other words, use of the front lever will distribute braking to front and rear according to need. If the rear wheel sensor detects lock-up, the ABS will release the braking action to that wheel momentarily before re-applying it.

Light front brake use will apply even lighter rear brake effort, if any at all.

 

[MIKE R]

Out of interest, what kind of boots do you use or size feet do you have?

Kai

Size 9 Altberg boots.

I have a brake extender from N/N. As the bike s a GSA, it is the serrated type and is not as long as the one that fits the standard 12. I have managed to bodge fit a standard 12 extender and it is better. At present I am considering modifying a standard 12 one (it needs a couple of grooves cutting out where the extender meets the height adjuster). Unfortunately the downside is that it will not allow the height adjuster to be used.

Thanks for all your replies.


Mike

 

[JayGee]

My take on this is that you should forget the rear brake pedal in an e-stop, maximum pressure on the bar "front" lever will get you maximum braking effect. Even with traditional unlinked brakes the rear is only going to contribute about 10% in an e-stop as the rear tends to lift whilst the front digs in and is where the real stopping power is. The linkage will give enough or maybe even too much rear brake when just the hand lever is used at maximum braking.

The rear is just for slow speed manouvering and off road work where the rules are completely different.

I've practiced a few e-stops and from about 60mph with just squeezing the lever ever harder there is a sensation of the rear brake having some intital effect but soon the rear starts to lift and all the braking is on the front. BMW designed this system so riders could stop quickly without having to try and modulate their braking between front and rear, it's designed so that you only need use the "front" lever. Earlier BMW ABS were fully linked and it made no difference which brake you used, they partially delinked it so that riders could apply only the rear for slow speed control.

Mine an 04 bike with servos but I suspect the same is true of the newer 07 bikes that don't have a servo (actually they do have a servo on the rear but BMW call it a pump and the system is far better fail safe)

 

[BBB61]

you don't have the 07 brakes though, or do you?

No, but I do have linked brakes and I suspect the only difference between the '06 and '07 systems is the servo assistance. The same brake calipers are used on both model years so I would imagine there is little if any difference in pad wear between the '06 and '07 models.

 

[cookie]

No, but I do have linked brakes and I suspect the only difference between the '06 and '07 systems is the servo assistance. The same brake calipers are used on both model years so I would imagine there is little if any difference in pad wear between the '06 and '07 models.

imagine away

i've seen quite a few people complaining on these forums about ludicrously high rear pad wear on 07 bikes (including me).

 

[BBB61]

And I've seen plenty of people on here complaining about high rear pad wear on pre 2007 GS's too

 

[conncarr]

Unlink my brakes please (in bad conditions)

My take on this is that you should forget the rear brake pedal in an e-stop, maximum pressure on the bar "front" lever will get you maximum braking effect. Even with traditional unlinked brakes the rear is only going to contribute about 10% in an e-stop as the rear tends to lift whilst the front digs in and is where the real stopping power is. The linkage will give enough or maybe even too much rear brake when just the hand lever is used at maximum braking.

Yes, on well surfaced, dry roads.

NO on muddy, cowpat strewn, gravelly, icey or wet roads.

Some conditions might require up to 70% rear brake (and correspondingly 30% front) to stop in the minimum distance without dropping the bike! You can't always choose your conditions for an emergency stop, but it's nice to be able to control braking forces accordingly.

 

[Deleted account 210609001]

I have an '05 bike. Mechanic at my nearest dealer reckoned that if you don't brake very hard very often, rear pads will wear much quicker, as they system initially starts with a relatively even split between front and rear, and only weights it towards the front when the brakes are applied hard enough for rear grip to become a problem. After 14,000-odd miles, I'm more than halfway through my second set of rear pads, whereas the fronts look virtually unworn.

Makes sense, I suppose, but can't say for sure whether this is correct.

I rarely use the rear brake pedal at all these days, unless I'm on a really dodgy surface. Although I had to do an emergency stop the other day and reverted to both brakes on instinct.

(I like to think I don't brake very hard very often because of my outstanding riding skills, exemplary anticipation and massive cornering speeds. In reality. I suspect I'm just slow. )

 

[Wapping]

Lifted from the BuMW blurb:

BMW introduced the world's first antilock brake system on a motorcycle via the 1988 K 100 RS. Over a decade later, the company has more than 200,000 ABS-equipped motorcycles worldwide and remains the only maker in the world to include ABS as either optional or standard equipment on all of its motorcycles.

Despite this industry leading position, BMW pushes braking technology a step further with the introduction of its EVOlution and Integral brake systems.

The EVO design provides significant improvements by means of reduced lever effort, improved braking power and reduced unsprung weight. Combined with EVO, is BMW's all-new linked brake system, which provides simultaneous operation of the front and rear brakes. This electro-hydraulic design differs from less-sophisticated, hydraulic only arrangements in two key areas. First, it dynamically monitors the front-to-rear wheel load to provide optimal brake balance. Secondly, its adaptive circuitry compensates for such variables as a changing fuel load or the additon of luggage and a passenger.

I take it from this that the balance between the front and rear brakes is not, say, a constant 75% - 25% but rather that it varies according to demand. This makes it different from, for example, the much simpler (cruder?) system on my old Blackbird's linked brakes (hydraulic only), where the front lever opeated a couple of the pistons on the front and one on the back (or whatever the ratio was) - whilst applying the back brake at the same time, brought the other pistons into play. Honda would have liked to have gone with the electro-hydraulic system as well but, so I am told, were scuppered as BuMW held the patents. The crafty huns apparently only granted licences to competitors to 'copy' the simpler hydraulic systems.

So to answer Mike R's question. Slam 'em on: the 'brain' in the machine will (should?) sort out the balance out for you. If you crash though it may, or may not, be your own fault anyway.