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Re: G-Force Tires Report and For Sale

To: "Robert M. Pickrell Jr." <brnrubr@midusa.net>
Subject: Re: G-Force Tires Report and For Sale
From: Byron Short <bshort@AFSinc.com>
Date: Thu, 18 Feb 1999 20:14:16 -0700
Robert M. Pickrell Jr. wrote:
> So for autocross and stock cars the BFG is a much better comparison to
> the Hoosier. It seems the G-Force is wearing fast for some people, but I
> am sure there are som die hard BFG fans out there that will counter that
> idea. Like Byron or Goeke.

Well, if you're gonna mention me by name...  ;-)

I haven't run on them yet, which is driving me crazy.  I've been too 
busy working on the G-Cube to even bolt on our new sway bar, much less 
get tires ordered, etc, etc, etc.  But I can tell you that I've seen 
GEEZ data on a series of back to back tests between the Hoosier and the 
G-Force, and it's very revealing.  Although both drivers *felt* faster 
in the Hoosier, and both felt that the Hoosier was *easier* to drive, 
both were faster on the clock on the G-Forces, albeit by small amounts, 
about 0.2-0.3 seconds on 50 second runs.  

Looking at the data revealed why.  The G-Forces produce MUCH higher 
transition rate numbers.   On the order of ~4.5g/sec vs ~3.5g/sec for 
the Hoosier.  Most have reported the tire's snappiness similarly.  But 
the real surprise was the peak lateral g's.  The G-force was 
consistently 0.05g higher in absolute peaks.  However, both drivers 
reported that the increased work of keeping the G-Force on the edge made 
them suspect that the Hoosier would maintain higher levels throughout 
the entire turn.  But it didn't.  While the margin between the G-force 
and the Hoosier closes as the sustain goes up (I compared at 1/2 second 
sustain and 1 second sustain levels), the G-force produced more grip at 
each level.  In fairness, though, by the time you get to one second 
sustains, the G-Force is only pulling 0.01-0.02g on the Hoosier.  

The conclusion we reached was that the G-Force telegraphs information to 
the driver.  Therefore the driver more readily feels when he is falling 
off the edge.  This results in the driver expending one heck of a lot of 
work to try to stay on that thin edge.  However, even when he feels that 
he's fallen off the edge, he's still often pulling more g's than the 
Hoosier.  In other words, the BFG makes you work by showing you where 
you can improve.

More data will be needed to see if this is a consistent result.  The car 
in question was a well sorted stock car driven by 2 different National 
quality drivers.  The car had about 1.2degrees negative camber, and 
weighed around 3000 pounds.  That day, on that course, with those 
drivers, we saw the subjective information matching what many have 
reported, but the analysis showed much more insight into the nature of 
the G-force tire.  At least one of the testers is a netter, so I'll let 
him speak up if he likes.

Maybe I *am* just a BFG die-hard, but I was pleasantly surprised by the 
results.  

--Byron


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