In a message dated 8/5/02 11:58:03 PM Central Daylight Time, "Brad Cox"
<COXB@tmfhs.org> writes:
<< Let's assume the "subject" is a typical nose heavy Honda Civic. With
respect to spring rates, some people go higher with rear rates compared
to front, while other folks will do the opposite (high front rates, low
rear rates), then still others recommed nearly identical rates front and
rear. And all on the same car! Everyone claims their way is very
effective. >>
I have also seen some very different setups, and have driven a couple of
them. What I write in here is based on how I drive and what I have seen. You
may not agree with my opinion, that is why there are so many different setus
out there. I have since switched to running rear drive, and the setup is very
different again, so I am re-learning.
<< I know the "enemy" of the FWD is understeer, but what's going on here?
I can't assume that a whole group of people is just delusional, although
I can be lead to believe that some of them don't know how to drive. ;-)
Do driving styles differ enough to create such a huge disparity? >>
Driving style has A LOT to do with the prefered setup. The fastest CSP
drivers usually have their cars set up very loose. Basically they are on the
edge of spinning on virtually every corner. The idea is that when you lift
off the gas the tail will get very loose and the car will rotate into the
corner. Then the driver has to apply throttle to transfer weight onto the
rear tires and make the car stop rotating. If done correctly the car will
actually be accelerating while near the cornering limit. This can be very
fast, but also explains why a hot driver will have cones and DNF's, then take
the lead on the last run.
<< How about traction? I can imagine that street vs. race tires might
effect the overall spring rates, but not necessarily the ratio between
front and rear rates. Is this correct? >>
Having the car set up with extreme rear roll stiffness will give the best
posible front tire traction to pull out of the corners. The inside front tire
will be loaded the best with all of the roll stiffness in the back, but there
is a serious practical limit. Once the inside rear tire is in the air, more
rear roll stiffness will have little effect. At that point increasing the
front roll stiffness will have more ability to reduce body lean. Whether it
is done with springs or bars does not seem to matter much. For very rough
surfaces, it seems that more bar and less spring works a little better, but
this is argued by many drivers.
Now what this means is that many front drive cars like very stiff rear
suspension to go fast, but it makes a greater demand on the driver. Slaloms
are far easier to drive with a car that has some push instead of always being
loose. This may bias the balance based on your local events. From what I
have seen on several cars, it all comes down to how much body lean the driver
will tollerate. The cars with the rear far stiffer than the front usually
lean more and have the inside rear tire well up into the air. Stiffening the
front rates closer to the rear makes the car lean far les, and as long as the
inside rear tire still lifts the weight transfer ratio front to rear is the
same and with less body lean the camber of the outside tires will be much
closer to static allowing for less static camber which gives better braking
and acceleration grip. The fastest cars I have watched only tift the inside
rear tire about an inch, but it is up there all the way through just about
every corner. It touches down as the throttle is pushed, just as expected.
Your mileage may vary, and how you throw a car will change what will be
fastest.
Gary M.
Old "1983" rear drive Celica in SM now.
Just faxed my Nationals entry
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