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Re: Spider Bite

In a message dated 9/21/99 11:13:25 AM Central Daylight Time, 
peterb@mysysltd.com writes:

> Regarding the debate as to it's existence, I have to ask if this is possibly
>  a flaw in an aging system?  Does the torsen suffer from poor or old gear
>  oil, or wear caused by same?

The first time I experienced it was in a brand new 90q with less than 1700mi. 
 The other times I experienced it was everywhere from 10k>220k.  We are 
talking about torque shift across the center axle of 56% affecting the u-o-u 
of a given chassis.  Wear and bad oil would either cause the effect to get 
better (less torque across the axles), or worse (more torque across the 
axles).  I don't find mileage has really any effect, get the combination of 
factors right, it shouldn't have any effect.  If wear, etc affects a torsen 
by 15% over it's lifetime, then we are talking a 50% shift in torque, or a 
63% shift in torque.  Either way, you only change when it becomes significant 
in the slip angle - wheelbase - cf - Trg matrix.

>  "Power on" has definitely pulled me out of this on an on-ramp - wet
>  conditions, car started to push, pushed the pedal down - not sudden or
>  hard - but quickly, and had the front end track true.  More power then gave
>  me a four wheel drift to nicely finish the adrenaline rush that came on 
>  the first hint of understeer. That was my 200TQ, an A6Q (98 model) thrown
>  hard in a parking lot cone course managed a nice four wheel drift - 
>  predictable and under power. Is this also a torsen in new condition or is
>  that haldex?

Torsen in both.  However, your best hope is a four wheel drift.  There will 
be a time with the right conditions, your best hope becomes your worst 
nightmare, BTDT.  When a torsen is fooled by slip angle differences across 
the axle, you *can* remain in an infinite loop where the device sends power 
to the front and rear axles as they speed up and slow down relative to the 
slip angle differences.  Controlling, rather predicting this device in all 
conditions is impossible, IME.  Too many variables to try to predict.  Glad 
it's worked for you so far...  My first warning to all, just when you think 
you can predict it, you find you can't.  
>  I know well the effect of simultaneous brake/throttle from my old Golf 
>  on the front wheel drive, but the power to TORque SENsing diff will send 
>  power rearwards and neutralize the effect of the breaking. (me-thinks)

What we want is braking to hit the faster spinning wheels.  That will catch 
with left foot braking on the U part of the pendulum, since the front brakes 
have  more power than the rears so slowing the fronts while applying power 
keeps understeer more predominant.  Still not a comforting concept...

>  Higher tire pressure at the back (or harder rubber compound) without
>  changing tire sizes should/might have the desired effect (nicely
>  demonstrated in RONIN) of power induced oversteer and/or the optimum for
>  all-wheel drive; four wheel drift/powerslide.

Hmmm, I enjoyed the chases in Ronin, but using them for any driving example, 
not with ya.  Higher pressure in the back will send the back out sooner, that 
really doesn't help your u-o-u.  Because the highest pressure you can put in 
the back, doesn't make a 60f/40r understeering chassis oversteer.  However, 
you can make it understeer more, much easier.  
>  Stiffen the rear suspension and take traction ability away from the tires
>  (pressure/compound) and I would think a reduction on the u-o-u "spyder 
>  would be in order.

Not my experience at all (I've put stiff linear rate c/o on the rear of a 
couple dozen 44 chassis cars, with no reduction in 'bite'), and really 
understanding the physics of what causes the bite, this really can't reduce 
it.  Just the when, not the 'if'.

my .02

Scott Justusson