[torsen] Re: [s-cars] "Correcting" understeer

QSHIPQ at aol.com QSHIPQ at aol.com
Thu Jan 18 12:56:03 EST 2001

In a message dated 1/18/01 10:19:32 AM Central Standard Time, 
Jani.Peltopuro at poyry.fi writes:
>  We Finns have a saying that goes something like "quotes like the Devil 
>  quotes the Bible", meaning you take one sentence and use it to argue your 
>  point. Which is, surprise surprise torque distribution. 

I don't see "oversteer" mentioned in the article listed.  This really has 
nothing to do with torque distribution (and frankly torque distribution all 
along is only a secondary or causal interest to me), it has to do with 
chassis dynamics.  

>  By definition, IMHO,
>  -Neutral is neutral, goes where you point it 
>  -Understeer goes straight in turns, or turns less than you'd like
>  -Oversteer it turns more than you'd want
>  Neutral is what you ideally would have, then it would be easiest to adjust 
>  the car's attitude by driving style to the preferred state of the driver, 
>  be that U or O. 

That would be oversimplifying things a bit Jani.  Applied torque makes a huge 
difference to the characteristics of the car.  At the limit of applying that 
torque to the ground you have O or U.  Then you have a device that affects 
how much of that torque gives you what chassis dynamic.  The summation of all 
this might indicate (and appears to from the articles) that you can reduce 
the inherent U characteristics of a quattro chassis by putting more meat in 
the front.  But, by definition they haven't changed to O characteristics, and 
your definitinon of "neutral" can't be applied quite so easily.  Less U in a 
U chassis, is less U, that's all.

>The fact is the modification makes perfect sense, at least 
>  to me, when considering 100% driving on track. The part about the VW-Audi 
>  Car article that annoys me is the comparison of rear roll bars between RS2 
>  and S2, since the weight bias is different,you can't directly compare 
>  diameters. RS2 has 56f/44, S2 has 60f/40.

You miss a couple of points.  Neutral doesn't go where you point it, 
sometimes quite the contrary...  A front weight bias car that is drifting in 
a turn isn't going where you point it, and it's understeer by definition.  
The problem with front heavy cars is that you can reduce U to a point, but at 
the limit of adhesion (and beyond) the neutral drift you experience is a U 
phenomen.  Secondly, the fact is that a stiffer rear end with a smaller ASB 
can achieve a car that doesn't LTO as much.  The article doesn't list spring 
rates of either car.   What the article is alluding to, is that to achieve 
higher effective spring rate MTM chose to go after the spring rate instead of 
the bar rate (they could have done either)  Consistent with street vs 
performance aspects of the RS2 vs MTM execution philosophy.  One has to 
question Jani, given the ease of availability of the RS2 part here, why it 
wasn't used.  In the context of rear ASB discussions vs spring rates on this 
list something to consider.

>  Sorry I don't have time to scan the German article now, or argue this 
>  further than maybe tomorrow, leaving for Bali on Sunday. Even Scott can't 
>  ruin my mood :-))
>  Regards,
>  Jani

Not trying to ruin anything Jani, only explore what was done and why.  This 
isn't something new, at the time this article was written, I had driven 
Graydon's execution of the same concept (and graydon kinda fell into it the 
same way if I remember the Z car wheel apps correctly).  The concept works, 
no question in my mind.  It is also quite consistent with what Jeff G has 
argued all along, if you tune a quattro with a FWD handling mindset, the 
benefits can be much greater.

All that said, it certainly would appear that one of the articles listed the 
wrong tire size.  I'll hold off exploring this idea further until we can get 
an agreement on that.


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