MR2 Oversteer

Description

The MR2, being a mid-engine car, has handling characteristics which
differ from most.  Oversteer, the tendancy for the back tires to lose
traction during a hard turn, can result in the back end suddenly 
becoming the front.  As the center of this discussion, we will not
label the *oversteer tendancy* a "problem", indeed, used properly it
is a valuable characteristic.

Rather, the substance of this discussion is the tendancy towards oversteer in
the 91-92 MR2 as compared with the 93-95 and whether the MR2 is
'tail happy'.

[Ed. - I suggest all posters to the MR2 digest avoid the
term 'tail happy' lest you are asbestos coated!]

It should be noted that neither the early nor late Mk2 has an
oversteering tendancy in normal use.  The rest of this missive
will be aimed at extreme driving; the edge of the envelope.

The Basics

In extreme cornering, as in all, the momentum and weight of the car
shift entering a corner, allowing the outside tires to increase their
grip on the road which enables the car to drive with the curve.
In the best circumstance the driver will neither accelerate 
or brake while in the corner preserving the momentum and weight 
characteristics.  

If, however, the driver slows or brakes within the corner, the momentum
characteristics will change and the weight of the car will shift towards
the front resulting in traction loss in the back tires.  If the shift is
drastic enough, the rear tires suffer a catastrophic loss of grip and
the back end of the car will break loose.  There are other instances
that will cause oversteer also, for instance, going over a large bump
while in a hard turn or having to suddenly slow in a corner because of
an upcoming accident  -  basically anything that results in a drastic change of
weight will almost invariably spin an MR2.  Of course this could happen 
in *any* car, the *degree* of the tendancy to oversteer is the point 
of examination.



The MR2

The 91-92 year MR2 has a different rear suspension geometry as compared
with the 93-95.  It is true that the change in geometry was intended
to reduce the tendancy to oversteer and most would agree that the 
modification does just that.

The hotly debated topic is whether the 91 MR2 has a "problem" with
oversteer.  I'm not sure that there is one answer to this question.
so best to enlist the comments of those who know.  Abridged comments from 
the digest are below:

"  With an *experienced* driver the '91 has 
better holding capabilities.  With its shorter (trailing) arms, the car 
is VERY responsive to all movements;  it is ADVANTAGEOUS to have control 
over the rear-end.  In corners the '91 holds 
harder than a comparably configured '93 suspension *if* you maintain your
speed.  Let up (on the gas pedal) once and the tail will wake you up and 
tap you on the shoulder.  

My feelings with the '93 is that for the general public the 
suspension changes were an improvement.  SCCA drivers typically drive 
the '91-92 models if they have a choice.  I feel Toyota made the (91) car to 
fit the vision of a production racer.  Realizing the general public 
needs saftey built into their cars (because they aren't competent 
enough drivers) Toyota made the suspension changes.  " 

					- Pete Feret (91T and 93T)

"  Yes, the rear suspension of the 91-92 is somewhat quirky for the 
uninitiated, but anybody with a strong familiartiy of rear wheel drive 
and power induced oversteer will relish in the enhanced 'point and shoot' 
driveability of the car. (Very quick through a slalom with the right rhythm.)

The nay-sayers of the 91-92 MR2 have never really driven one hard.  It 
requires a special finesse that rewards a skilled driver. "

					- Kip Anderson


Regarding the uninitiated driver or those who drives the limits but
prefer predictability:

"  If you like driving the car at the limits you may want (a 93+ or
modified 91 which is more like a 93+) because it is a bit more predictable 
and forgiving.  That is not to say, the 91-92 suspension is not predictable,
but rather the time from rear end breakaway notification to actual breakaway 
is a little longer for 93-95."

					-Jeffrey HoSee (91T)


[End comments]

So, the choice between a 91 and 93 with regards to oversteer is a personal
one.  If you can master the characteristics of weight, momentum, and
cornering then possibly the 91 is for you.  If you are unsure or want
a more predictable oversteer response, then a 93+ (or modofied 91) would 
probably be a good choice. 

Overall, one should remember that *both* cars have a tendancy towards
oversteer.  The degree of that tendancy is the difference between
the two years.  In either case, one mistake during extreme cornering
may have dire consequences.


rev A