Just thought I'd add my bit since I've probably had more seat time than most
this year and have run R1's, G-Forces, and Kumhos (haven't mounted the Hoosiers
up, yet). I also don't have any contract or brand affiliation (guess I don't
rate :-)). Anyway, here are my as objective as possible impressions.
G-forces:
It irks me a little to hear some comment about the "facts" on the tire when
they only put a few events on a set. Between Teresa and I we've gone through
the better part of four sets this year (~200 runs on various surfaces). It was
quite awhile before I realized how much we were fighting the tire because our
setup and pressures were so wrong. One day we ran R1's back to back with the
G-forces and were almost a second faster on the R1's. The light bulb wasn't
really the time differential, but how much *easier* the car was to drive on the
R1's. Much softer rebound settings on the shocks and much lower pressures
(than BFG recommends) made the car *much* better with the G-forces. We were
able to *drive* the car rather than constantly worry about the G-forces
abruptly breaking loose. Anyway, I'll try and summarize....
-G-forces are incredibly stiff, resulting in great turn in and dynamic response
-the quick response can be very difficult to control unless you compensate in
other areas (pressures, shocks)
-they are very susceptible to mistake damage (lockups, spins)
-with proper break in (a good heat cycle before running) I expect to get about
25% less life out of a set compared to R1's
-They're harder to set up on lighter cars. I drove an MR2 Turbo which was a
bit heavier than my car and it was a lot less twitchy with a near identical
setup. This just means I think you may not have to make as much adjustment on
a heavier car to soften things around the stiff tire.
-Even with a better setup, I still find it difficult to drive them consistently
at the limit. When you have limited runs, this can be a real problem.
-They're performance/$ is not nearly as good as the Kumhos.
-They take a little longer to heat up, but are more resistant to overheating.
-Reward a very smooth driving style. Aggressive inputs coupled with the fast
response will get you in trouble.
-I've found that as little as 1 psi can make a dramatic difference in the
response of the tire. Just being "close" may not be good enough.
Kumhos:
We've only put maybe 30-35 runs each on the Kumhos so the database isn't as
good. Also, as others have commented, they don't make the same size tire for
our car as BFG so that is a factor.
-Turn in and response of the Kumhos is not nearly as good as the G-forces.
It's like driving a grippy street tire in comparison.
-That said, the Kumhos are great at letting you push the car to the limit of
what the tires can handle and stay there. On Kumhos, I feel I can go out and
worry about how I'm going to drive the course, rather than just try and make it
through without any major mistakes.
-Wear is pretty good, though not any better than we used to get out of R1's.
In 50 runs on concrete, we've taken a full tread set (properly heat cycled)
down to no visible tread (no circumferential grooves).
-I haven't noticed any significant difference in braking than with the R1's or
G-forces. They're all relatively heavy tires.
-You can't beat them for the performance/$.
-They seem very susceptible to overheating and want to be kept relatively cool
to continue to grip well.
-They reward aggressive driving and make it very easy to keep the car pointed
in the right direction.
-We can flatspot them as well as any other tire, they just have more tread to
make up for it.
All of the above IMHO, of course.
-Andy McKee
MR2 CS
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