>Listers,
>I'm kind of ignorant when it comes to discussing or understanding
>handling as it
>relates to TRs or any other car for that matter. I was hoping the racers,
>autocrossers and generally aggressive drivers could chime in about
>what it takes
>to make a TR handle well and what compromises are inevitable when doing so.
Just thought I'd clarify one thing right off the bat that I think is
very important
the laws of physics pay no attention to national
boundaries. In other words, making a British car handle is no
different than making a Japanese car handle. All the same rules
apply, regardless of where the manufacturer of the car is, or WHO the
manufacturer of the car is. Of course, some makes and models will
lend themselves better to certain solutions and not to others.
>
>For those of you that know, how does the complex interaction of springs,
>bushings (rubber, urethane, nylatron), shocks and swaybars (oops! anti-roll
>bars) front and rear effect handling? How is this different on IRS suspensions
>(4A-6) and solid axle (2-4A)? Also, how do ride height, castor, camber and
>toe-in modify the equation? Tire sizes and composition, temperature, humidity,
>moon phase, day of the week, stem cell research...anything that I missed?
Of course it would take an entire book to answer all these questions,
and I do suggest that you go pick up a copy of Fred Puhn's 'How To
Make Your Car Handle' for just that reason. But I'll give it a shot,
anyway. As a rule, the thing you sacrifice when you make
modifications for the sake of roadholding is ride comfort. Of
course, you gain a measure of safety because your car becomes far
more stable under all sorts of conditions and as such it becomes
easier to control. Fitting uprated springs, urethane bushings, big
anti-roll bars and stiffer shocks all have the effect of degrading
the ride comfort on ANY car. I've chosen not to be bothered by such
things
a Triumph is not a Cadillac and so I don't mind the rough
ride. But all those modifications can have a PROFOUND effect on the
car's behavior and on roadholding. Go get that book (library
maybe?). Your car's steer characteristics will be transformed by
these modifications. 'Steer characteristics' refers to whether your
car has a tendency toward understeer or oversteer while cornering.
Understeer generally refers to the condition where your car is not
turning as tightly as the steering wheel angle would suggest. In
other words, the front end is 'pushing' or 'plowing.' Oversteer is
the condition where the rear of the car comes unstuck before the
fronts do, resulting in what you generally see a lot of at sprint car
race. Usually, the objective is to set a car up so that it is
'neutral' or perhaps oversteers just a bit. Most road cars are
designed with a lot of understeer built-in, because an understeering
car is generally easier for the huddled masses to control.
Lowering ride height lowers the center of gravity, primarily. (for
'real' race cars this also has an aerodynamic benefit) Tweaking
castor, camber and toe all affect the steer characteristics as well.
Camber is particularly useful for dialing out understeer, however too
much negative camber on a road car will have you wearing out tires
prematurely, so don't get carried away.
Tires are a big issue for me
I sacrifice what would probably be far
better roadholding because on a road-going TR6 I think low-profile
tires look ridiculous. Generally, the shorter the sidewall of a
tire, the better the handling will be. (and the tire will transmit
much more shock into the car, as well which translates into even
worse ride quality.) A TR6 looks GREAT with the big, tall tires they
were supplied with. My TR6 wears 205-70/15s, which is the closest
you can get to the OEM tire size. Your choice of true 'performance'
tires in this size range is extremely limited, because with such a
tall sidewall there's really not much point to it. Your really
sticky tires are usually disappear from the tire catalogs when you
get past an aspect ratio of 60. So I just put some Toyo Z800 Ultra
tires in the size I mentioned above and call it good. Incidentally,
tire pressures front and rear also affect steer characteristics to
some degree.
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