RE: another quattro goes down & locked diffs underbraking

[glen powell <gpowell@acacianet.com>]

There are at least a couple of different effects going on here, and I'm
sure I'll miss some, but here are a few, both good and bad:

good:
1) with both diffs locked the braking power is nicely distributed between
    all of the locked-together wheels, if one wheel's brakes tend to grab first 
    or more Vs the others, the locked diffs will prevent this one wheel 
    from locking and the other locked-together wheels will force this one to
    keep rotating till all the locked wheels loose traction completely,
    also known as 'poor man's ABS'

bad:
1) if you do brake hard enough to lock one locked-together wheel you
    will lock them all and you will instantly loose all control and stability

2) if the above occurs you will kill the engine eliminating the possibility
   of instantly applying power to try to power out of the emergency and
   if traction is rely low simply releasing the brakes may not get the
   locked-together wheels rotating again as they must overcome the
   inertia of the entire drivetrain, all 3 locked-together wheels and also
   the inertia and compression of the engine - that's a lot in a low/no
   traction situation such as wet ice

3) if the above happens it will be very difficult to regain control because
    now you must overcome the inertia of all three locked-together
    wheels and also the inertia of all of the diffs, prop-shafts, axle-shafts,
    engine, etc, Vs if only one wheel locked you would only need to overcome
    the inertia of the one wheel and axle-shaft that locked

Nasty huh?

-glen

<You have locked that rear diff as well? (might have made the spinn 
worse as it makes it easy to lock up both rear wheels under braking)>

I thought I was following this thread (interesting real world info) 
fairly well until the above statement.  I can't make the jump to ease of 
brake lock up being attributable to whether the wheels are driven or 
not.  Are you saying the locked diff helps transmit braking power wheel 
to wheel as well, implying that locked diff allows brakes to be more 
efficient than when seperated by open diff?
Mike

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