R1200GS Servo/ABS brake failure tests

[BBB61]

My test results (which I posted months ago) did contradict Aurelius's in that I found no detrimenal effect on stopping distance with the servos off. BUT my stopping distances were longer than his, which leads me to suspect that when I was doing the "servo on" test I was not braking at full efficiency. I only tested at 40mph but the stopping distance of my bike with and without servos was half the Highway code figure.

I'm not surprised that your stopping distances were longer than the ones Aurelius posted. He is claiming a braking distance of 14 feet when stopping from 30mph. With a braking force of 1g, that will equate to a braking distance of 30 feet. Few road going cars and motorcycles are capable of achieving braking forces in excess of 1g. This site makes interesting reading and confirms the g force under braking that most vehicles can attain is up to 1g. To stop a bike in a distance of 14 feet from 30mph suggests a g force of just over 2g. That just doesn't add up.
This is why I find the data supplied by Aurelius is flawed.

Bob

 

[Aurelius]

I'm not a "diehard advocate" but I probably lean in that direction.

My test results (which I posted months ago) did contradict Aurelius's in that I found no detrimenal effect on stopping distance with the servos off. BUT my stopping distances were longer than his, which leads me to suspect that when I was doing the "servo on" test I was not braking at full efficiency. I only tested at 40mph but the stopping distance of my bike with and without servos was half the Highway code figure.

Mouse, if you found that braking with the servos disabled made only modest differences in stopping distance, I can guarantee you that you weren't using the servo/ABS brakes to anywhere near their full capacity. Try it at a very slow speed first and you'll see what I mean. At say, 10mph, apply both brakes as hard and as fast as you can. You should hear the tires lose traction instantly, at which point the ABS system takes over. The bike will buck and lurch like a wild bull, with the tires squealing as they continually lose and regain traction. You'll feel like you're about to be thrown from the bike, but suddenly it will stop as if you'd hit a stone wall. It takes a while before you get accustomed to it, so I wouldn't advise you to try doing a stop from 40mph the first time; work your way up to it. I used this method of braking to simulate a "real world" panic stop and to eliminate variations resulting from progressively applying brake pressure, the way we're taught to do it. Consistent technique is paramount to obtaining reliable measurements, and the way to achieve that is by relying entirely on the bike's ABS system to modulate braking.

I'll be looking forward to your results.

 

[BBB61]

At say, 10mph, apply both brakes as hard and as fast as you can. You should hear the tires lose traction instantly, at which point the ABS system takes over.

On a ABS equipped 1200GS, there is no need to apply the front brake lever and the rear brake pedal. All the braking can be done through the front brake lever thanks to the semi integral braking system.

Bob

 

[obewan]

Improved brakes

Interestingly the non servo result at 30 mph is well within the Highway Code stopping distance of 46 feet. Even though these distances were "set" in the dawn of time, it shows how much brakes have improved when a bike will stop in less than 2/3rds the distance and it is considered bad!


Paul, I believe there are two factors in operation here.

1. As these are tests the riders have set out a marker for where to start braking so the "thinking time" is not included in the overall stopping distance

2. Whilst brakes have doubtless improved I believe the Highway code has not be changed as others argue that reaction, or Thinking Time, has not improved and so overall stopping distances have not dramatically reduced with modern brakes.

I wonder what would happen with the above test results if the tests were carried out with the rider being told when to brake by a third party (a mate on the other end of an intercom system). Of course this becomes more complex as the third party has to identify the point where they first said "stop". But it would perhaps give a better idea as to the relative braking distances with and without ABS/Servo when reaction time is taken into account.

 

[Gonzo]

Re: Improved brakes

I wonder what would happen with the above test results if the tests were carried out with the rider being told when to brake by a third party (a mate on the other end of an intercom system). Of course this becomes more complex as the third party has to identify the point where they first said "stop". But it would perhaps give a better idea as to the relative braking distances with and without ABS/Servo when reaction time is taken into account.

Anyone got a data-logger?

There isn't a teeny-weeny chance we're over-engineering this debate, is there? I'm clear that this is a VERY serious subject................however, I don't need a the highway code or a tape measure to tell me that, on my morning commute, if I've planned to stop or manoeuvre based on my NORMAL braking power being available and it suddenly and dramatically isn't - I'm probably going down unless I'm very lucky or highly skilled (the former occasionally, the latter never!)

I also love the brakes and the confidence they give me - and will continue to enjoy and trust the bike. I believe that I'm more likely to be decked by a cage-driver in London than brake failure!