7" vs 8" wheel update

[Alan Stamper <stamper@iwaynet.net>]

Here is a follow up for all you auto-crosses following the 7" vs 8" wide
wheel comparison on my Scirocco 2.

It turns out that the answer is not as clear cut as I thought.  You may
remeber that I had decided that the 7" wide wheel combo was faster
combination on my car.  This is not completely true.  

I remounted my new (used actually) BFG's onto my old 7" wheels.  The
result, slower than the eights with the same set of tires.  I have a few
ideas why, maybe you guys can come up with a few helpful thoughts also.

I bought these BFG's from a friend of mine.  He purchased them new 2 years
ago and ran about 6 events on them (about 24-30 runs).  He then parked his
car and stored the tires until I bought them.  There is very little wear on
them and they look almost brand-new.  

Here is a list of ideas:
1.  This one is pretty easy, the tires have not been shaved and are at full
tread depth.  I can have them shaved locally for $60.

2.  This is the first set of BFG's I've put on the car that have had the
"cure" for the EGOD syndrom.  They are also the first set that I have had
that were made in the mold BFG created specifically for the 215/50/13 tire.
 The original was an 185/60/13 mold with a spacer added to the center.


The car has a decent balance, but behaves very differntly than before.  My
guess is that the stiffer sidewalls in the non-EGOD tires has reduced the
allowable slip angle in the tire.  In order to get the same amount of
oversteer as before I've had to really up my rear tire pressures.  I am now
running tire pressures in the ranges of what Shawn recommended.  This setup
feels O.K. but is really slow.  I just ran my first divisional of the year
and got my but seriously kicked.  Usually I'm the second or third fastest
car in the class and within 3/10ths of a second of the winner.  I was off
by over 2 seconds on each days course last weekend!!  This is not good!

At this point I'm going to try 2 things.  The first is to shave my BFG's.
Second, I'm going to try some of my buddy's used Hoosier bias-plys on my 8"
wheels.  These tires are 8/10" of an inch shorter in diameter than the
BFG's.  I've calculated that it I will be reving about 4% higher at any
given speed compared to the BFG's.  I will also have 4% less top speed in
any gear.  As a comparison the rpm difference between a 4K tranny (in the
car) and a 9A is 9%, with the 4k turning more RPM at speed than the 9A. 

Has anyone else tried this hoosier on their car?  I'm wondereing if the
increased acceleration and almost 1/2" lower stance that these tires will
give will make up for the speed I will loose in the top end?  Any
alignement recommendations for the bias-plys?

Sorry to be so long
Thanks
Alan
#17 DSP Scirocco (84)
87 16V Scirocco (newly designated project car)
89 240 Volvo wagon (driver & major parts getter!)


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