So now, the meat of the message, what your ABS equipped bike CAN'T do:
Can certain conditions make ABS a killer instead of a life saver?
ABS only works with the bike straight up or with VERY limited lean. If you think you can apply the brakes in a lean like you can straight up and think the ABS will save you, IT CAN'T. ABS systems have no "lean angle sensors" to work with the ABS and limit brake application while leaned over. Remember, even a moderate lean angle uses a lot of traction. If you add braking while leaned over you can still loose traction and ABS can do nothing to save your butt. Leaning and ABS braking combined could PUT YOU DOWN!
Keep in mind, ALL ABS systems are intended to maintain vehicle stability and have nothing to do with reduced braking distance. On a bike, ABS ONLY applies to straight line stopping. It is still up to you to keep your head/eyes up, and apply steady progressive braking effort. If you think ABS systems will make you into some kind of Uber-Braking God you could be rudely awakened by a meeting with a Buick grill. The braking is still up to you, ABS simply improves your odds of survival.
Now, THIS IS CRITICAL, and really think about this: in a car with ABS, you can mash the pedal all you want and steer the car clear of an obstacle. On a bike with ABS, if you hammer on the brakes and engage the ABS, and then think you are gonna steer around the grey-hair's Buick bumper, YOU ARE GOING DOWN!!!!!! Remember that bike ABS systems have no lean angle sensor to modify the ABS function while leaning, and a bike HAS to lean to manuever. Leaning in all its glory requires a lot of traction. If you think you can use any of that traction for an ABS stop I pray for your survival. ABS is solely for straight up stops.
So gramma turns the Buick in your path and stops. You hammer the brakes and the ABS kicks in. Then you try to swerve to avoid impact while still on the brakes? Sorry, traction gone, face plant on the hood or ground. ABS or no ABS, the old rule of seperating braking and swerving STILL RULES! This is one scenario where I think ABS could be a killer if you think it does the same control functions as in a car.
Here's another one. Let's say you are riding a nice straight stretch of road, when suddenly a truck ahead pulls out from the Sand/Gravel Pit driveway in your path. You apply the brakes on the clear dry road and sense the ABS engage. But as you get closer and still braking, the bike is now on a sloped sandy apron near the driveway. The front tire now slides down the slope with ABS doing all it can, and the bike has achieved a slight lean. This is a situation where the front tire could now lock up if brake pressure is maintained.
Do speed variations between each wheel sensor and the speedometer effect the ABS controller? Making it default to standard or residual braking? As far as I know, there is no link between the ABS controller and the Speedo on any bike. As I described in my earlier message, the ABS system determines bike speed by getting signals from both wheel speed sensors and calculates a MUCH more accurate real vehicle speed from that info. A speedo is way to inaccurate for that.
ABS is ALWAYS comparing wheel speeds any time the bike is moving just over walking speed. When braking, a variation in wheel speed greater than 20% less than the vehicle speed will enact ABS on that wheel.
If you were to fit one oversize (diameter) tire on your ABS equipped bike, it could mess up the ABS if the resultant speed sensor info was not within expectations of the controller algorithms. If both tires were increased the same diameter it should not matter. But an error signal from one sensor, say due to an oversize tire could cause a fault and the ABS would revert to standard braking and record a fault code. It is also possible that a fault code repeated over and over to the ABS controller could become PERMANENTLY burned into the ABS system memory. In essence "frying" it. I uh, found out the hard way.
Speed variations between each wheel sensor is exactly how the ABS determines whether or not to engage. Let's say you are very adept at spinning the rear wheel through a low traction turn (sliding the bike feet up, no braking), the ABS would sense a broad speed differential between the sensors, but because it also would not sense applied brake pressure (brake system pressure is also a function for ABS engagement) it should not record any fault. Same for a fast take-off with rear tire spining.
How does brake pressure applied and controlled by the user affect ABS, and how can that adversly affect the ABS controllers function? Again, the ABS control is based on 20% wheel slip DURING BRAKING for either tire. No matter HOW you brake, gentle or hammer it on, if the ABS senses 20% wheel slip it will engage ABS control. this applies for any surface, dry road, asphault, concrete, snow, leaves, sand, gravel, oil, anti-freeze, you name it. If the bike is vertical and braking, and one or both wheels slip at the -20% compared to the bike speed, ABS will engage.
Because the amount we brake is dependent on our skill level, preference, traction available, and all the other factors, ALL the ABS knows is whether one or both wheels are "slipping/sliding" under the 20% thresehold below the bike speed. You are the real brains in the braking system. So it is STILL up to you. ABS helps, but don't bet your life on it. |
19-07-14, 23:18
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