RE: awd vs rwd braking

[Eaton Dave <dave.eaton@minedu.govt.nz>]

> 
> Date: Wed, 21 Oct 1998 09:19:04 -0500
> From: Luis Marques <marques@rtis.ray.com>
> 
> I have to agree with Scott that braking performance has less to do about
> which wheels are driven and more to do with the weight distribution
> under braking and how big your contact patches are.  All else being
> equal (read equal weight, wheels and tires), the car that approaches
> 50:50 weight distribution while braking at over 1G will have the best
> performance.  In other words, something like a Porsche 911.  RWD or
> AWD.  With the rearward static weight bias, more weight is available at

ummm, the porker is nowhere near 50:50 weight distribution.  also large
contact patches tend to work against you in the wet.  to much rearwards
weight distribution though and you'll get snap oversteer once you turn the
steering wheel.  basically also any car that brakes at 1g brakes at 1g,
regardless of the weight distribution.  as posted my 20v posted 1.09g with
it's g60's and mintex pads...

> the rear under braking allowing the rear end to do more of the work. 
> Any car with a 50:50 or front-biased weight distribution will have less
> traction available at the rear to let the rear brakes work as much as
> the fronts.  Hint: if you want to know what car has the pottential for
> better braking, look at which one has the biggest rear brakes.

with 50:50 weight distribution, the rears aren't working anywhere near as
much as the fronts.  the ideal for braking in a staight line would be a
*rear*wards weight distribution.  just like a porker 911.  this is where the
torsen with it's shifting of engine torque forwards assists by taking the
engine braking torque from the rears.  the newer "active" setups do this
also...

> 
> Oh, about the gen. I quatto, a locked center diff doesn't split torque
> 50/50, it varries between 0-100% forcing the front and rear ends to runs
> at the same speed.  

yes, so this has the effect of forcing braking torque through the rear
wheels.  which is exactly not what you want....

What this does is it acts as a "poor man's ABS"
> preventing premature lockup.  It will also brake better than a torsen. 
> Now, if we wanted the ultimate handling car, we would want 50/50 weight
> distribution under cornering and 50/50 under braking.  We would need a
> ballast that moves back and fourth inside the car.  Humm... a certain
> DTM Mercedes comes to mind.

no the locked centre (no abs) will not come close to a torsen (w/abs) setup
in braking terms.  in the wet? nope.

the m-b was an interesting concept, and one which seems to work pretty well
in practice....

dave
'95 rs2
'90 ur-q