Tuesday, September 2, 2008

About a common misconception.

I went to a mechanic near my place to tighten the front brakes of my Bajaj Super scooter. IMO, the brake shoes have pretty much worn out. I was complaining to him about the the brakes not working well etc. His comment on my plaint surprised me quite a bit! He said 'rear brakes are the important ones, front brakes are just for support'
I have heard a similar statement from more than few people. It seems to be a common misconception that rear brakes are to be used to do major braking and the front can be used for little assistance. Doing so is inviting trouble! Of course, for four wheelers, the driver cannot control how much braking force is applied to which tyres. The problem remains only for 2 wheelers.
A lot of people even think that pressing the front brakes will make their bike slip, which actually is exactly opposite of what happens(unless the braking is done on a sharp turn at an inappropriate speed). Due to weight dynamically shifting from front to rear during deceleration, the front tyre is loaded and, only a small amount is friction(traction) remains between the rear tyre and ground. At that time, if the rear brake is used more than the front, the rear wheel gets 'locked' i.e it stops spinning, and this is the worst thing to happen to any vehicle! The vehicle will go out of control and will usually skid on the road. The front wheel always has more traction during braking, so the front brake must always be used and not the rear one. No wonder, disc brakes are put on the front wheel rather than at the back.
Cars and high end bikes from Honda, BMW etc have an Anti-lock Braking System(ABS), which continuously monitors the wheel rotations. If the system senses that the wheel is about to 'lock', the brakes are released(even if the brake pedal is pressed by the user) so that, the wheel gains some traction and the vehicle does not skid. ABS overrides user command for his own good. Actually, ABS reduces the overall braking efficiency a bit. A skilled rider can bring his bike to halt in less distance and time without ABS than with ABS. I've heard that, TVS India is coming up with a bike having ABS.
Some bikes have disc brakes in the rear too(Bajaj's Pulsar 220 has). Discs are excellent for braking, but if not used carefully on the rear, they can exacerbate the problem of skidding.

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Rohan said...

i wonder if this is correct for scooters like bajaj. Bajaj has wierd design and the weight distribution is lot on the rear side and i dont think it changes a lot while deceleration in case of bajaj; in others it might change. like M80, kinetic etc.
also the wheels are so small that i alwways fear 'turning while braking' (worst of all).
yeah i do understand skidding is a prob, so a combo of both brakes is the best, but 30-70 use in favor of rear.
Saying this i admit that i have always used front brakes on my bicycle and pulsar. both had almost no rear brakes.

Anonymous said...

ABS brakes shorten stopping distances not lengthen them :)