Re: 7" vs 8" wheels (long)

[trnsfrma@ix.netcom.com (Shawn C. Meze)]

At 09:43 PM 4/30/97 -0400, you wrote:
>Here's one for all you auto-xers.

I can hear Mannix drooling...... :)

>I recently purchased a set of MRT 13" x 8" wheels for my 84 Scirocco DSP 
>auto-xer.  The car used to hace a set of 13"x7" reveloutions...............
>I've done everything I can think of to make the car work.  The problem is
>that the car doesn't in a corner.  Before I could control the direction of
>the car by throttle position & left foot brakeing.  The car rotated very
>nicely. Under power the car would pull into the corner.
>With the new wheels it always has a push.  I also can't get the tires to
>roll over to the area where they need to be.  


Well, for one, BFG's dont roll over very much. Stiff sidewalls. Very stiff!


>Here is a list of the old & new setups
>
>Old
>13"x 7" reveloutions with 225/50-13 bfg R1's
>Front pressure - 32 lbs
>rear pressure - 28 lbs
>front camber - neg 2? (all I can get)
>fron toe - 1/8" out
>shocks front/full soft - rear/full hard

>New (this is the best I've found so far)
>13" x 8" MRT (1/2' more offset than the rev's)with 225/50-13 bfg R1's
>Front pressure - 22 lbs
>rear pressure - 16 lbs!
>front camber - neg 1.5? 
>fron toe - 3/8" out
>shocks front/full soft - rear/full hard


Why did you go from 1/8" to 3/8" toe out?? That quite a change in the world of 
autoX. 

As I said before, the sidewalls in a R1 tire are extremely stiff. Just as a 
sidenote, I have one racewheel that leaks air. (Loses all the air in about 4 
days) The last time I went racing, I mounted the tires the night before and I 
didnt know it was flat until a few minuted later when I put a gauge on it. It 
looked a little low, but the pressure gauge read 0lbs.

So, going to a lower pressure isnt helping, especially the rear. I run 30 lbs 
front 34 lbs rear. (Sometimes I even run 29-28 lbs front and 30-34 rear.) Those 
numbers work the best for me (on a 13X6 wheel). Now, by going to a wider wheel, 
you have loss some of the side to side tire flex that it had with a narrower 
tire. The wheel is now optimized to that size tire your using. You should be 
kicking some serious butt, but, like anything else, its gonna take a little bit 
of time for you to learn how to be fast on the new setup. As a result, the 
steering inputs are gonna need to be even smoother for the tires to do their job 
for you. BFG's dont like to be suprised with jerky steering. (or so I learned 
after running on Yoko's for 2 years!) 


>With less camber the tires roll to close to where they need to be, but they
>do not have an even temperature across the suraface.  The old set up had
>very even temps & tire wear. I keep lowereing the front pressures bu I'm
>getting nervios at how low they are getting.
>Any suggestions woul be appreciated.
>Alan


Well, what are the tire temps, do you know?? Thats kinda important too you know. 

HTH!



Shawn

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