Quote:
Originally Posted by Alex
Purspeed - can you expand upon that a little? Applying the rear brake, sometimes a fraction of a second before applying the front, is used to settle the rear suspension and bring it down slightly so in fact less weight shifts to the front. That technique can in fact keep the bike a little more balanced in non-emergency stops. But that seems to be slightly at odds with what you're saying...
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Most modern bikes get 100% braking from the front. Think stoppies. The friction of the tires to the road is the biggest factor in reducing braking distance. So, tire technology is key for improvement in braking (other than thermal conductivity in transforming mechanical energy into heat within the brake pads, calipers, floating rotors, etc.).
When you begin to brake (by either squeezing the front or rear brake lever on a motorcycle) weight shifts to the front of the bike. This prevents one from locking the brake.
This is why using the rear brake as a standalone brake is not suggested. It locks far too easy because the weight will transfer to the front of the bike rapidly causing the rear to lock.
So, if you first apply the rear brake, you shift weight to the front (in race applications, you are either accelerating, braking or turning 100%...or a combo thereof), and then apply the front brake now that the weight is shifted.
Some experts argue that you do not need to use any brakes at all (think Valentino Rossi & Keith Code) when corner carving or that braking doesn't give you a net lower lap time. But, for those of us mere mortals, tapping the front or rear brake (I like rear because that is weighted before I begin the braking process) transfers weight to the front and then you can firmly squeeze the front brake for maximum braking potential (engine braking not included).
Any input in the bike can potentially be a destabilizing force (things in motion tend to like being in motion...newton, et all), so being smooth with your inputs is key.
If you are coming out of a turn, the oscilllaitons from the "third" spring (the frame) depending on the material, structure and inherent dampening abilities of said stuff may unsettle the rear (you see this in racing quite a bit...not so much with 250GP though), but this would not relate to braking too much.
The rear is unsettled by friction loss (fore aft) and the tire searching for friction with lateral movements. This happens in both acceleration and braking.
When forcefully braking, using the rear brake can settle things a bit, as well.
Most MotoGP racers do not use their rear brakes, however...69 Hayden does though (and considered a bit strange by that virtue) but that has a lot to do with his roots in dirtbike riding...KEntucky.