Re[2]: Most dangerous braking situation...

[jmbrodsky@domain.elided]

        Guys, In all the Bicycle racing and League of American 
     Wheelmen certs, and Motorcycles, etc, classes, they've all said 
     that a rear wheel lockup is the result of brake bias too great to 
     the front.  Solution, let off the front brakes for just an 
     instant and grab them again.  Worst thing is to grab too much 
     front in a two-wheeler.  Same thing has always been taught in the 
     comp driving classes too.  Now, I don't understand the "i didn't 
     have time to blip the pedal' or 'How am I supposed to let up on 
     the pedal ina crisis?' stuff.  The first time I drove Mom's New 
     Jeep Cherokee (no ABS at the time) it was unfamiliar to me, but 
     an idiot pulled out and I had to slow from 50 to around 20mph in 
     no space at all.  I distinctly remember hearing the tires chirp, 
     then none, chirp, quiet, chirp, etc. as I did this.  I have been 
     using the technique for years, since my dad taught me from his 
     racing days.  
     
        Now, the question becomes, how much of a pedal 'blip' do you 
     need?  Only enough to reduce the braking pressure to let the 
     wheel turn again, and then grab pedal again.  An instant in your 
     mind is an eternity in actuality, and I must've heard the tires 
     do the move 5 times when I made ths panic stop.  It's natural for 
     me by now.  And this is exactly what ABS does.
     
        The front wheel lockup usually ends with a violent crank of 
     the front end pulling you into danger worse than the rear end, I 
     thought.
     
        Maybe I don't understand.
     

     -Joel Brodsky
        www.physics.arizona.edu/~jbrodsky

         '76 IHC Scout II Spirit 345/tf727 RE8000, Cibie40s, custom 
                rear tire rack, 6 different color body panels.
                Not much sport, all utility.
         '75 IHC Travelall 150 4wd 392/tf727 Hummer brush guard, 
                3/4T rear springs, Hella Rallye 2000s, Con-Ferr 5x7,
                Class IV hitches front and rear, 3" Exhaust.
                1st Place, Rocky Mountain IH Rendezvous,
                3rd Place, Tulare IH Western Regionals.
         '74 IHC Travelall 150? 2wd 392/tf727 "The 'new' one"
                Factory AM/FM, Cruise, Tilt, AC, Captains Chairs,
                Rblt: Alt, carb, fuel pump, ps pump, water pump, dash,
                seats, rear door, starter, master cyl, what could be left?

-----INCLUDED MESSAGE FOLLOWS-----

Author:  tjhemh@domain.elided at mime wrote:

Guys:
     
General consensus is rear wheel lock up before fronts is to be avoided at 
all costs.
     
Rear wheel lock up tends to cause rapid spin out that you cannot control. 
Front wheel lockup causes loss of steering, but vehicle tends to just 
"slide forward" in a straight ahead fashion. Go check any brake system book 
such as HP's.
     
On top of that, due to the physics involved (wheight shift) the front 
brakes are doing the majority of the stopping in the first place. That, 
combined with different operating pressure requirements between disks and 
drums, is why we have a proportioning valve in the first place.
     
Tom H.