Servo Assisted Brakes - Safety Announcement

Danny · Ask Me About Stoppie School Joined: 26 Jan 2003 Karma :

This is a safety announcement that all applies to any bike with servo assisted brakes.

Never, ever, buy a bike with these brakes, they are imo extremely dangerous as I found out earlier today.

While riding my BMW K1200R to work this morning I started to approach a roundabout and as normal applied the brakes.
A split second after I applied the brakes the ignition key turned itself to the off position.
This meant that I only had 'residual braking' as the servo assist doesn't work when the ignition is off.
At best, 'residual braking' gives you 25% of your normal braking power.
I very luckily managed to avoid the cars on the roundabout and eventually stopped in the middle of the roundabout.

I later found out that on my bike and possibly others, a small electrical fault such as a loose brake light wire can cause the ignition to turn off or reset.

NB. the bike did the same thing in November, but I thought it must be a 1 in a billion chance of it happening so just ignored it.

Servo assisted brakes are pointless anyway, as a normal good quality calliper can easily stop a big bike with one finger.
So people. please don't buy these stupid bikes, they are death-traps!
So much so, that BMW are phasing these brakes out.

The Rest of My Day:
After my own bike trying and failing to kill me, a cabbie thought he'd try and kill me too by pulling out on me 5mins later. Rolling Eyes

I called BMW Breakdown when I got into the office and asked for recovery to my dealer, they said they have to send out a technician first.
He arrived 11am, then proceeded to call me a liar (not in so many words) on two separate occasions. He eventually agreed to get a recovery truck.
BMW Breakdown quoted me a time of 1:30pm for the recovery truck to arrive.
I called the free breakdown policy I got with my E-Bike insurance and they were there within the hour.

When I got to BMW Oxford I dealt with the head of after-sales who was extremely helpful and did everything in his power to help me.
This included lending me a helmet as I'd forgotten mine at work.
Giving me a R1200GS as a loan bike; I should have gone for the F650 as the R1200GS is FAR to tall for me.
The tip of my boots only just touch the ground; also I think the bike may actually be taller than me Embarassed

He also gave me a discount on a pair of gloves.

I have to say that I was and still am very shaken by this experience, I can deal with people pulling out on me etc.. but not my brakes randomly failing. Confused

..... · Quote Me Happy Joined: 15 Jan 2005 Karma :

I'd be giving the bike back to them for a full refund.

That is not on and not worth risking your life for.

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Just about every car made has servo assisted brakes.

When a servo fails pull harder on the lever.

mr.z · World Chat Champion Joined: 04 Feb 2004 Karma :

I very much agree, there prone to failing for no reason at all and thats a bad bad thing (as clearly illustraited here!)..

Not only that when they do its bend over time since allot of servo/abs brakes can't be fixed at home, which is fuck all use when your in the middle of nowhere with no working brakes (anyone watched the long way arround Shocked

)

"safety" feature like these really do worry me Confused

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>RidingSkills<->Tech Tips<->MyBikes<

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

As said, if power assist fails, pull harder.

A (female) friend of mine called me up last week saying that her car brakes no longer work. She was driving along and the pedal went hard and had no braking power.

So, had a poke under the bonnet and found that the vacuum pipe from the pump (diesel) to the servo had split at each end.

New unit fitted and got her to test drive it. As she pulled out of the space she complained that the brake pedal was too soft and the brakes were too powerful. Quick test myself to confirm what they were like and they were normal servo assisted brakes.

Turns out she'd been driving for years with a split hose and hardly any brakes and it took a total loss of assist to make her question it. (and passed MOT's which raped her for new suspension arms, but not faulty brakes) Rolling Eyes

She's now amazed at how easy it is to brake . . . Shocked

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"because one stroke isnt enough and four strokes waste two"

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

'tis all true - you can get exactly the same amount of braking effort without the servo just by pulling harder. You're using the same master cylinder and the same calipers and all the same brake hardware, the only difference being the servo isn't helping you push.

I was a bit surprised (never having seen a bike with a servo) that there isn't enough of a vacuum reservoir to give you one good go on the brakes after the engine has cut out.

What I thought you were going to say was that the diaphragm in the servo had failed, resulting in it eagerly feeding all of your brake fluid to the hungry engine. Now, that's funny and I get the cookie.

finpos.

Stalk · Brolly Dolly Joined: 26 Dec 2005 Karma :

Give me a cookie!
Iveco 35:8, normal hydraulic brakes with servo assist. (vacuum pump and tank for servo) If the tank is empty first thing in the morning the first application of brakes can sometimes be before the vacuum is built up in the tank. Both feet on the pedal, arse in the air and hanging off the wheel. Its not stopping.
It has happened to me on more than one occasion and I am never ready for it.

Finglonga · World Chat Champion Joined: 27 Jul 2004 Karma :

Got ABS on my bike and I always turn it off in dry conditions as I can out brake it...In the wt it is handy though.

As for servo brakes the new 1200GS's are being made without servo's as there have been that many complaints about them failing. Have ridden one that has failed I can understand how people could panic but the brakes do still work (as said above). You just need to squeeze that bit harder.

I must be getting old, I remember and have owned cars without servo's. Embarassed

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Andy Sez....
F.Y.Y.F.F.

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Danny · Ask Me About Stoppie School Joined: 26 Jan 2003 Karma :

Joe, I will be writing to BMW and asking for that or for a different bike that doesn't have these brakes.

Sickpup, I was pulling as hard as I could on the front brake lever, while I was stamping as hard as possible on the rear brake.
As I mentioned earlier, when the servo is not functioning you get roughly 25% of your normal braking force.
This is the figure given to my by the head of motorcycle after sales at BMW Oxford.
I would estimate that this was the sort of braking force I was getting.

Stalk · Brolly Dolly Joined: 26 Dec 2005 Karma :

But the servoless brakes require more force than the driver can produce. End result vehicle not stopping.
Go on, compromise, Half a cookie?

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Danny · Ask Me About Stoppie School Joined: 26 Jan 2003 Karma :

Sickpup, I assumed that figure was calculated based on the strength of your average person.

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Danny

I'm not accusing you of being a crap rider or any such I'm saying you were surprised, you probably even looked down at the master cylinder to see what was happening. Anyone who has forgotten to pump the lever after changing pads has done the same thing. I have.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

I've always appreciated the simplicity of the braking system on a 'normal' bike. It is so utterly direct.

More to the point, I can't see any need at all for a servo assist on a motorcycle. You can stand a modern 1000cc sports bike on its nose using two fingers and you could certainly lock the front wheel at three figure speeds if you so desired.

It is adding unecessary complication to a system that already works perfectly adequately, I've never heard anyone complain about not being able to pull their brake lever hard enough to stop. I've ridden bikes with totally shit brakes too, but that is nothing to do with the force applied and everything to do with the braking system itself.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Danny · Ask Me About Stoppie School Joined: 26 Jan 2003 Karma :

Stinkwheel, I couldn't agree with you more!

Sickpup, out of interest does the MOT power test take account of the weight of the bike?

plugger147 · World Chat Champion Joined: 13 Mar 2005 Karma :

My first (legal)car was a Mk1 escort that had no servo It also had drums all round, after I changed the front struts for 2.8 capri ones with disc brakes but still no servo the brakes were the best i've ever had on a car. more feel than i've had in a modern car and half the hastle.

It's just the same as towing somebody they automatically think the brakes don't work and jump on the pedal as hard as they can. They still work just need more force as said although in a moment like that I don't know what i'de have done.
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Tristan the wrote: just whipped off my trousers to find a big bruise on my arse, caused by matt rear ending me...

Danny · Ask Me About Stoppie School Joined: 26 Jan 2003 Karma :

sickpup · Old Timer Joined: 21 Apr 2004 Karma :