Handbook Insert for bikes with ABS Brakes

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Starman

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I got a letter today from BMW UK with an insert page/leaflet for the handbook concerning the capabilities or lack of them of the Integral ABS system with the request to take my bike to a dealer for a free brake test/check. This is a result of a couple of isolated cases in Germany where riders of the press produced an extreme off-road situation where the brakes failed completely.

Basically the insert leaflet says that you have to have a fully charged battery and the correct dynamic load distribution (their words not mine) to achieve maximum braking by applying the correct pressure.

All very well, however one paragraph seems a bit scary:
'In emergency braking as it is often taught, in which the brake pressure is generated as quickly as possible and with all possible force, the dynamic load distribution cannot follow the increasing deceleration and the braking force cannot be completely transferred to the road. The ABS has to intervene to ensure that the front wheel does not lock up; this reduces the brake pressure and the braking distance is extended' !!!!

Scary stuff: so in an emergency stop, you'll hit whatever obstacle you're trying to avoid anyway cos the ABS cant cope with the sudden pressure and the braking distance is extended........ wasn't ABS supposed to increase safety ???

Well, off to the dealer to get them brakes checked, even if they wont help...... :thumb

Martin
54 GS12
 
Wots a handbook? :nenau

had bike for several months wth not a sight of one!!!
 
It's a worry!

I also recd, perhaps with all other 1200 users the insert.

Yes the battery has to be kept fully charged. So all you lot with the bike 'stored' should put on trickle charge.

What is scary is the comment that 'extended' use (heavy) would drain the battery very quickly hence the loss of braking or efficiency. It mentions not suitable for track use. What about alpine usage! It could be a very long drop.

None of my cars with ABS have mentioned this.

Perhaps the weight reduction small battery/alternator is a wee bit near the mark.
So I think I'll drag my foot instead
 
Gramps said:
None of my cars with ABS have mentioned this.
Click to expand...

AFAIK the servo on cars uses stored air-pressure to power the brake servo. The 1200 (from the sound that it makes when you operate the brakes), uses an electric motor to power the servo. Though I'm willing to be corrected.

(I got the leaflet too)
 
JerryP said:
AFAIK the servo on cars uses stored air-pressure to power the brake servo. The 1200 (from the sound that it makes when you operate the brakes), uses an electric motor to power the servo. Though I'm willing to be corrected.

(I got the leaflet too)
Click to expand...

I believe that in cars it is generated by the Inlet Manifold Depression.

I guess my leaflet must be on the way.

Went out last night and some of the roads were very greasy, therefore I was glad I had it just for peace of mind....

Piggers
 
ABS does not decrease braking distances in the dry. In optimum conditions, ABS will always increase your braking distance. It's not some sort of magic device that makes your brakes more efficient - in fact it makes then less efficient.

The only purpose of ABS is to stop the wheels locking on surfaces with poor grip - this helps keep control of the machine but it can not decrease the optimum braking distance. Of course, on a poor surface, the stopping distance with ABS will probably be less than the stopping distance with a locked up wheel.
 
JerryP said:
AFAIK the servo on cars uses stored air-pressure to power the brake servo. The 1200 (from the sound that it makes when you operate the brakes), uses an electric motor to power the servo. Though I'm willing to be corrected.

(I got the leaflet too)
Click to expand...

No - only Shitroen use air pressure. Wife's father had one which (unknown to everyone) had a leak in the reservoir. Wife took the parked car out of gear on a steep hill before starting the engine, Brakes wouldnt hold - she couldnt get enough pressure on the residual braking, and she had to deliberately drive it into a wall to stop it.

Air brakes should fail safe but not the French.
 
Well, that feels so much better............

................to have received my handbook insert today. :thumb

The fickle finger of fate has, however, pointed in my direction as, would you Adam'n'Eve it:

..

..

..

..

..

..

..........my servos have failed today. :eek

All by themselves sat in the office car park. Luckily, it was pretty obvious as soon as I got on the bike, helped by the rather noticeable flashing light.

60 miles home certainly helped me to explore the, er, characteristics of residual braking.

Any tips for me to investigate apart from the obvious brake lever against the guard and BMW Recovery?

G
 
Any tips for me to investigate apart from the obvious brake lever against the guard and BMW Recovery?
Click to expand...

I'm told that low fluid level, even an apparent one caused by dropping the bike, can set off a warning
 
Last Friday at the testing ground in Beds, whose name escapes me, a rider performed an emergency stop from 70mph on a police R850. The only strange thing is that he turned off the engine and did not have any servo assistance. Remember it is only petrol engines which run the servo from the vacumm in the inlet manifold. Diesel engines require a pump as well, but appear to have none of the surrounding 'problems' that have been mentioned.
 
Gonzo - check both brake lever switches, the footbrake switch can get trapped on the adjustment bolt on the footbrake lever. Hard to describe, should be obvious when you look. Also check your ABS sensor cable (left hand side of the front wheel). If the cable has been fitted incorrectly the brake disc can abrade through it.
 
BillWright said:
Last Friday at the testing ground in Beds, whose name escapes me, a rider performed an emergency stop from 70mph on a police R850. The only strange thing is that he turned off the engine and did not have any servo assistance. Remember it is only petrol engines which run the servo from the vacumm in the inlet manifold. Diesel engines require a pump as well, but appear to have none of the surrounding 'problems' that have been mentioned.
Click to expand...

Perhaps the brake servo pumps fitted to diesel engined vehicles are driven directly from the engine, rather than electrically? The trouble is lack of space on a bike to fit something similar, I imagine.

I've tested emergency stops on my 1200 with no servo assistance. The brakes feel very wooden, and you have to pull like hell, but they stop you well enough. A better way to do it, rather than turning off the ignition while moving, is to unplug the front brake lever switch before turning on the ignition. Obviously then you'll have no servo assistance until you reconnect the switch, so be careful :)
 
Starman said:
...

Scary stuff: so in an emergency stop, you'll hit whatever obstacle you're trying to avoid anyway cos the ABS cant cope with the sudden pressure and the braking distance is extended........ wasn't ABS supposed to increase safety ???
...
Martin
54 GS12
Click to expand...

No, what it means is that the ABS is doing its job by, in effect, pumping the brakes. Just like you would do if you found yourself in a car skidding on a slippery surface.

It releases and reapplies the brakes very fast to prevent front or rear wheel lock.

Nothing new, just badly worded.

We got the same thing here in the US as well.

Jim :cool:
 
Just be aware that, if your servo assistance has failed and you decide to ride it home/to a dealer etc, they may find that the servo cuts in again without warning.

As a result, the mega pressure you have been applying to brake without assistance is suddenly multiplied several times by the now active servo, resulting in an unexpected emergency stop to the surprise of all those behind you (who hopefully have very good reactions!).

Happened to me when the front brake light switch began working intermittently. The servo assistance went, and then arrived again with a bang just as I was braking to turn into a side road. Stopped dead and the alert white van man behind me just pulled up in time to avoid running me over.

Eek.
 
JimVonBaden said:
No, what it means is that the ABS is doing its job by, in effect, pumping the brakes. Just like you would do if you found yourself in a car skidding on a slippery surface.

It releases and reapplies the brakes very fast to prevent front or rear wheel lock.

Nothing new, just badly worded.

We got the same thing here in the US as well.

Jim :cool:
Click to expand...

And ... therefore, gives you control over where you're going. Hopefully then not into whatever caused the emergency.
 
My understanding of ABS is that it helps prevent the wheels from locking up in an emergancy situation, which in turn allows the rider to avoid hazzards by steering round them. If you are in a skid you will continue on the same course whatever you do with the handle bars (steering wheel). The pay off is increased braking distance which for some riders/drivers could be a problem.
:bounce1
 
Starman said:
All very well, however one paragraph seems a bit scary:
'In emergency braking as it is often taught, in which the brake pressure is generated as quickly as possible and with all possible force, the dynamic load distribution cannot follow the increasing deceleration and the braking force cannot be completely transferred to the road. The ABS has to intervene to ensure that the front wheel does not lock up; this reduces the brake pressure and the braking distance is extended' !!!!
Click to expand...

The way I read this is:

"Sorry everyone, but we have unfortunately over-servo'd the brakes on our bikes so they stop really well in normal use. Grabbing a handfull however will definitely lock up your front wheel, causing the ABS to release and reapply, by which time you will be half a mile further down the road than normal and in need of fresh underwear." :D
 
We can say the same about any high performance braking system (I'm thinking of my Aprilia RSVR) - over brake and you lock up (except if you're wise enough to invest in an ABS option). This doesn't just apply to BMWs.
 
Sorry guys, but it would appear that some skill is still required to ride a bike:)
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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