car braking question...

[Journer]

ok, so most of us should know what electronic brake distribution (EBD) is. simply put, the computer adjusts individual wheel braking depending on the situation. now, one thing i've always wondered, has there ever been any manual brake distro systems?

what i was thinking, is motorcycles always have front and rear brakes. when racing, the way you use them is extremely important. want to take a faster, tighter turn? then pull the front brake and it'll pull you into it. need to slow down and straighten out? a little more back brake helps.

now, this is a lot simpler on a bike because of the way you ride and control it, but, has something similar been implemented on a car? i mean, does it not make since to be able to control the front and rear wheel brakes differently? drifters often utilizing the hand brake (rear, non hydraulic, break line) to help whip the rear end out. but what if you had a brake peddle (or hand brakes on the steering wheel) that if pushed in the center hits both brakes like it always would. but, if you so desired, you could hit the left for rear and right for front. i suppose if you could eat with your hands you could make a four peddle version for all the wheels, but that is just too complex.

what does AT think?

 

[Zenmervolt]

With the amount of braking force required to stop a car, a hand-operated service brake would not work well. (Ever tried to use only the emergency brake to stop?) Additionally, aside from very specialized uses like the drifting use you described and line locks (which actually are effectively the same as what you describe for drifting, they just use a solenoid) there aren't really advantages to driver-controllable variation in brake force distribution (a driver simply cannot react fast enough to make this worthwhile, it takes the computers used in EBD systems to make them truly useful).

That said, cars have been using proportioning valves to vary the front/rear braking force for decades. In street cars these are usually fixed and are set up such that the front brakes will tend to lock before the rear brakes (this as a safety measure to prevent oversteer). For racing they make adjustable proportioning valves that can be adjusted to suit certain racing circuits, brake pad types, tire type, weather, and driver preference, but these are not typically adjustable from within the car; they are pre-set during race prep and tweaked between practices.

Even some motorcycles are using proportioning valves to automatically activate both brakes when either is applied.

ZV

 

[thomsbrain]

Journer, one really good reason why we don't have this feature is that most people (including you) don't yet understand how grip or driving dynamics work.

Pull only the front brake harder in a turn and you will understeer more, not tuck into the corner. As Zenmervolt said, this is one reason that the front brakes get so much more bias in street cars; to help them "safely" understeer rather than oversteer. Pull the back brake harder and you're more likely to oversteer, not understeer. You had it completely backwards, so be glad you didn't have to find that out the hard way!

There is a great book from Skip Barber Racing School that explains (among other things) how tire grip works with combinations of forces (like turning while braking). I'd highly recommend it to any driver. There are countless other little lessons in that book, from understanding racing line strategy, understanding how the internal mechanics of a drivetrain necessitate certain techniques, etc. Just a fascinating read that made me a much more conscious driver in general.

 

[Journer]

you sure this isn't different on a motorcycle? because when i pull the front brake it digs me deeper into the turn. hit the back brake and the bike tries to straighten out, but since it is in a turn this usually ends up badly if you back brake too much. i happened to have learned this one the hard way... >_<

also, what is the name of said Skip Barber book?