This week, we’ll return to steering systems after learning how to go around corners effectively last week.
Conventional steering systems for motorcycles involve telescopic forks. However, there are a few unconventional layouts that have advantages over traditional forks.
Dive under braking
One is BMW’s Telelever suspension, which they use on products like the R1100R. The Telelever suspension, to cut a long story short, reduces dive under braking. This ‘dive’ is nothing but the way the bike’s front goes down when you press the brakes. This compresses the forks, which makes it harder for it to deal with bumps, and it also changes the way the suspension behaves ever so slightly. What this means is that the motorcycle’s steering characteristics will change ever so slightly under braking, which may not matter to the ordinary Joe, but certainly does to riders of high-performance bikes. Another relatively unknown suspension system for a motorcycle’s front wheel is the ‘hub-centre steering’ system.
This steering system consists of two suspension arms that join the chassis near the centre, and not at the top of the front of the frame as in conventional forks. It isolates the forces that act on the front wheel when a rider brakes or turns, which makes the motorcycle’s behaviour more predictable.
The downside is that it has got lots of parts and linkages, so steering feel isn’t its strong point, which is probably why production motorcycles like the Bimota Tesi 1D and Yamaha GTS1000 didn’t sell too well, despite the former being designed by Massimo Tamburini (who needs no introduction to the enthusiast — to the others, think ‘Ducati 916’) and the latter coming from a manufacturer that has icons like the YZF-R1 and V-Max in its lineup.
How power steering works
Power steering systems for cars work by taking driver input from the steering wheel and amplifying it via a hydraulic or electric pump to turn the wheels. Hydraulic systems generally offer better feel, but electric assist works in favour of fuel economy, which is why manufacturers are gravitating towards it. There’s a very simple reason for this: the hydraulic pump has to keep running all the time, while the electric pump can switch itself on only when the steering wheel is turned. This is why it is dangerous to coast in a modern car with the engine switched off — without the assist, it is almost impossible to turn the wheel.
Variable braking assistance
Some cars now have what they call ‘variable assist’, which means that the amount of assistance provided is varied. This is done because the more the assist, the less the ‘feel’ one gets through the wheel. This is one reason why racecars usually don’t have power steering. Cars with variable assist reduce the assistance at speed, since the faster a car goes, the less you need the assist. For example, BMWs are great to drive quickly around corners, but parking them in South Mumbai will have you develop good upper arms in no time.
Some cars like the new Honda Accord have a system that increases or decreases the amount the wheel has to be turned for a certain amount that the front wheels turn, depending on speed. For example, if you turned the wheel all the way over to the right at a standstill, if it took a half turn (180 degrees), it’ll take a whole turn (180 degrees) at speed.
Now that you know all this, have fun with corners!