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Stop Right Now: ABS vs. The Man

ABS: good for those that wants it. Or is it even better than that? Can you handle the truth? Be prepared, as Prof Jon Urry and his performing lab rats demonstrate to us all the startling reality

Honda has stated that by 2010 most its bikes will have 'advanced braking systems'. Being a caring, responsible manufacturer Honda is doing its best to reach the best solution to cut bike accidents and deaths. But is ABS the way forward? Do we really need ultimate control of the brakes taken away from us?

Honda isn't alone. Most manufacturers are tinkering with ABS right now, and BMW have been at it for years. The problem with many bike ABS systems is that they aren't all that sophisticated. Bikes aren't like cars. If one of a car's wheels locks all the system needs do is momentarily reduce braking force, allowing the tyre to recover grip. Not a massive drama as a car has four large contact patches and reduced braking to one isn't going to affect the total braking force much. And car systems have been in development for years. The first car with ABS was a Jensen FF Interceptor launched in the late 1960s. Mass-produced bikes didn't have ABS until the BMW K series in 1988.

Crucially, bikes stop differently to cars. Most of a bike's braking force goes through the front tyre, so if the ABS reduces braking to prevent a skid, this has a very noticeable affect on the overall braking performance. Also bikes lean over. When a bike leans the tyre's rolling circumference changes, which confuses the sensors if the brakes are applied. The only real way to combat this would be to use gyroscopes, but then the costs and weight of the ABS system skyrockets. So bike manufacturers have to develop ABS that can deal with the unique circumstances of motorcycle braking.

So are the current systems actually any good? Not that long ago a decent rider could out-perform the ABS fitted to most bikes - the systems really were pretty crude. To see how things have moved on, we took two near-identical Triumph Sprint STs, one with ABS, one without, and put them to the test in damp-to-wet conditions. James Whitham acted as our experienced hand and TWO staffer John Hogan as the not so experienced one. A VBox GPS data recorder was also used to accurately measure speed, distance and time.

MAN V ABS

To give us some baseline figures Whit braked from an indicated 80mph (a genuine 75mph) to stationary on both bikes as hard as he could, first using both front and rear brakes, then only the front, only the rear and finally using engine braking alone.

Test 1:  Both brakes combined, 75mph to 0mph

ABS 4.18SEC, 227 FEET
NON ABS 4.35SEC, 237 FEET

Using both brakes together James stopped faster with ABS than without, which was a surprise to us. How come, James?
"With the ABS the rear's making a big difference. When you're braking hard the ABS kicks in and reduces the braking force on the front, which pushes weight onto the back as the forks uncompress. I was holding both brakes hard so the back would then be working to stop the bike even harder for the time before the front recovered grip. It almost see-sawed back and forth as the ABS reduced then increased the braking. On the non-ABS bike I lost this extra bit of braking from the rear. I concentrated
on the front's grip while keeping pressure on the rear constant."

Test 2: Only using the front brake, 75mph to 0mph

ABS 4.75SEC, 265 FEET
NON ABS 4.6SEC, 258 FEET

With only one brake James beats the ABS. He tells us how... "Once I had the bike settled with some braking force I only had to concentrate on what the front tyre was doing. I can feel when the tyre is about to lock and release the brakes slightly. The thing with the non ABS bike was I could reach a constant, near the limit of traction, and keep it there. With the ABS you jam it on and when it thinks its going to lock it releases, then brakes again, releases, etc, which loses time. But I was impressed by the level of braking before it kicked in, and it took less concentration."

Test 3: Only using the rear brake, 75mph to 0mph

ABS 8.15 sec, 435 feet
NON ABS 7.8 sec, 409 feet

Once again James beats the ABS. Once again he tells us how: "It doesn't matter so much if the rear wheel locks. A five-metre front wheel skid is bad; with the rear it isn't. Using just the rear I simply braked until the tyre locked, then backed off a bit. I could be a bit rougher than with the front because I wasn't worried about locking, but I beat the rear ABS for the same reason as I did the front: constant braking rather than on/off ABS."

Test 4: Engine braking only

28.8 sec, 905 feet

James: "I never thought I'd bloody stop."

MAN V MAN V ABS - THE GREAT LEVELLER

Although James did beat the ABS on two out of the three tests, the ABS won when he used both brakes together. But can ABS bring an average Joe's braking to a level close to James'?

Test 1: James v John 40mph to 0mph

The first test simulates probably the most common scenario for hard braking. As John discovered on his GSR recently, a lot of accidents happen in town at relatively low speed, for example the classic 'Sorry mate I didn't see you' situation, or when a pedestrian walks out in front of us. For this test it's stopping  to a standstill from 40mph, and it's in the wet.

ABS James:
2.25 sec, 71 feet
ABS John: 2.25 sec, 71 feet
Non ABS James: 2.28 sec, 71.9 feet
Non ABS John: 2.42 sec, 77.2 feet

John on the ABS bike has stopped quicker than James on the non-ABS bike, just, and matched his braking exactly on the ABS bike. ABS has equalled the riders' braking abilities. How?

John "I simply put all my trust in the ABS. I was confident that all I had to do was hit the brakes as hard as I could. With the non ABS bike I was really scared of locking a wheel and falling off. Beforehand I was thinking of all I knew about braking - getting the bike settled, starting gently then increasing the force, all that. But it isn't easy. On the non-ABS bike I simply couldn't force myself to brake that hard as I was sure I would fall off, while with the ABS I had complete confidence. The ABS took away all the worry of locking the front."

James "On the 75-0 test I could find a constant point and hold the brake there to beat it, but on this test the ABS was working faster than that. The ABS reached a maximum point faster than I could and because the speeds were slower and the distance shorter it made these crucial milliseconds count."

Test 2: James v John, 75mph to 55mph

For the second test we simulated a potential motorway incident -you know the kind of thing, when traffic brakes hard and slows suddenly, but without coming to a stop. In this test the riders slowed from 75mph to 55mph, again in the wet.

ABS James: 1.04 sec, 102 feet
ABS John: 1.17 sec, 111 feet
Non ABS James: 1.1 sec, 104 feet
Non ABS John: 1.22 sec, 118 feet

John couldn't match James's times - 75mph is very fast when you want your right hand to grab as big a handful as possible. James, used to the extremes of racing, had the confidence to grab. He's also a bit mad. Note the differences in James's times and distances between ABS and non ABS - only two feet and 0.06 seconds, but that could be the difference between hitting a car or not. The seven-foot difference in John's slowing distances is more significant - he'd hit the car much harder.

John "I knew the ABS would work, but the speedo was reading 80mph and that is fast. I tried to trust the ABS, but there was simply no way I was going to grab the brake and hope for the best. The ABS took seven feet off my stopping distance, which is good, but I probably could have stopped faster if it was a real emergency and I knew I had no choice."

James "The initial grab is the time when the tyre is most likely to wash out. I'm not surprised the ABS was better on this test. I've fallen off at high speed and it isn't nice, so I'm cautious when first applying the brake. With the ABS I had the confidence to simply hold the brake on. It took some doing, but worked."

TECHNICALLY SPEAKING

Anti-lock braking systems on motorcycles all work along similar principles, with sensors measuring wheel speed and adjusting braking force if needed. Honda and BMW lead the way with braking technologies. It's no coincidence that both those manufacturers are pretty good at making cars too
.
TRIUMPH
TRIUMPH'S ABS system operates through a single module to control each wheel separately. Once again, the ABS uses sensors mounted on a fork leg and swingarm to take readings from a toothed wheel - 72 teeth on the front wheel and 60 on the rear. When wheel deceleration exceeds a certain value the ABS
activates valves which divert brake fluid flow back to the master cylinder in a closed loop system. These valves can open and close up to 200 times per second - the pulsing sensation riders may feel when ABS is operating is these valves working.

At the moment Triumph's ABS module is quite bulky and the firm is looking to refine the system and offer it as an option on most models. Until then ABS will only be available as an option on the Sprint ST.

HONDA

Honda's ABS and linked braking systems have been developed to fit various models across the range. Hondas's ABS use a crank rather than a valve to regulate brake pressure and eliminate pulsing at the lever.

The Combined Braking System (CBS) activates both front and rear brakes from both controls. Pull the front brake lever and four of the front six caliper pistons are operated. An actuating arm on the left-hand caliper raises as the pistons apply, activating a secondary master cylinder which, via a proportionate control valve (PCV), operates the centre piston on the rear caliper. Push the rear brake pedal and the two outside pistons on the rear caliper operate, while a PCV diverts pressure to the
centre pistons at the front. The front left piston cuts in just after the right to reduce fork dive.

BMW

BMW has developed its Integral ABS using technology developed over the last 20 years. As effective as the previous EVO system was, owners didn't like it. The idea of minimum lever input for max braking force was fine in theory, but in use the servo assistance was too great when applying small amounts of lever pressure.

The new, servo-less ABS uses sensors to count notches in a toothed wheel. If the system recognises that wheel speed has decreased rapidly it operates the ABS.

It's also semi-linked. The rear can be operated independently of the front, but 40% of the rear's power is applied when the front is operated. BMW will integrate this system with the new Automatic Stability Control (ASC). Eventually most BMWs won't  wheelspin, skid, wheelie or stoppie.

CONCLUSION

There is one major flaw in our test results: both riders were settled and ready to brake hard. They
knew what was about to happen.

But real life isn't like this. In an emergency you have fractions of a second to react, then brake. And that's when the ABS can become a lifesaver. As James says, the most dangerous part of braking is the initial bite. This is the point when you are most likely to lock up and crash. James may have been able to out-perform the ABS on a few occasions, but add in adrenalin, panic and unscheduled sudden stopping and the results would have been different.

This test showed that an average rider's braking performance is greatly enhanced with ABS. In both tests John stopped faster with ABS, and in the two final tests James did too.

"I was really impressed with the Triumph's ABS system," said James, "but we were braking on a smooth, flat, surface in a straight line. Add in a few bumps and ABS does start to show its limitations. I'd want a system that isn't there except for the time I really need it. Then it would be a lifesaver."

John: "In the dry I still wouldn't want it, but this test has highlighted the reasons for having it in the wet. It undoubtedly made me stop quicker. Just a few feet can make a huge difference in an emergency situation."

ABS is certainly here to stay. With all of the current manufacturers developing systems it can only get better. If the next generation of systems can offer the benefits without the drawbacks, it will be hard to find an argument against it.