A lot of people new to the Mini-Z world
have the same first question: “Which Mini-Z should
I get?” Well, the choices are MR01, MR015, MR02
and F1. Due to their much taller center of gravity,
the MR01 and MR015 are passable if you are just bashing
around or want to use a particular body that doesn’t
fit on the MR02. For racing, you only have 2 real options,
the MR02 or the F1. This article is dedicated to the
differences between the MR02 and F1 chassis.
Originally, I thought that the F1 chassis was far inferior.
I raced in the F1 class only because I was an F1 enthusiast
and loved the way their Mini-Z counterparts looked.
I couldn’t figure out why, but the F1 chassis
just wouldn’t handle power like the MR02, getting
squirrelly with anything more than a stock Mabuchi motor.
Recent testing showed something interesting though.
For some reason, my F1 laptimes were tantalizingly close
to the top MR02 times, sometimes even faster, regardless
of how slow the car felt. I could only imagine how quick
they might be if the car actually felt fast! Armed with
my piqued curiosity, I headed for the track to determine
the cause for this unexplained speed and explore the
limits of the F1 chassis.
With any form of racing, the most important aspect
of tuning is TIRES. If you don’t have the right
tires, then you’ll literally be running around
in circles. My previous logic was that since we were
indoors (no threat of overheating) on a relatively forgiving
surface, the hot ticket would be to run the softest
tires possible. I chose Kyosho 10 degree rears because
of this. I noticed that when the tires wore down to
slicks, they had more grip and a more predictable traction
envelope. I determined that the increased progressiveness
was due to the reduced squirm of the tire after the
tall grooves had worn off. I thought that the increased
grip was simply a function of a larger contact patch
once the grooves had been worn away, but in hindsight
I was way off base on this assumption. Thanks to some
input from fellow racers, I made a leap of faith and
it paid off.
By testing Kyosho 20/23 degree grooves and slicks,
I discovered that the flex and deformation of the grooves
actually generated MORE traction than their slick counterparts
on the RCP surface. But everything in moderation. Deformation
in excess causes an unpredictable breakaway at the limits
of traction, especially in transition. The sweet spot
for traction-generating deformation for the rear tires
seems to be 20 degree grooves. The 10 degree tires from
Kyosho (and especially Atomic) have far too much squirm
and make the car a handful on corner exit. With the
Kyosho 20 degree grooves on a Speedy NM-powered F1,
you could abuse the throttle with NO wheelspin on corner
exit. The car simply hooked up in the rear and fired
out of the corner, even more easily than a stock-motor
F1 on 10 degree tires. The “shopping cart”
feeling was now gone, replaced by a much more neutral
steering characteristic. This led me to the following
conclusion: with the proper tire selection, the F1 chassis
is faster than the MR02. But how and why?
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