Originally posted by AutocroSSer:
[QB] More details :
Moving the arms back (extended arms) does a few things geometry and weight wise....NONE of them good!
- Worse weight distribution (more front-biased). Besides hurting handling on a car that is alredy front biased (albeit not as bad as an F-body), it isn't helping your launch either. There's a reason that folks are moving that battery to the TRUNK and not out on the edge of the front bumper </font>
- Springs/shocks now cocked at more of an angle (cocked spring angle means the spring is no longer straight up and down, but rather sort of "sideways"). Can be solved on the shocks with longer bolts/shims, requires custom spring perches to be installed on the axle.....which presents geometry problems all it's own (your springs aren't really "on top" of the axle now!)</font>
- Shorter wheelbase = better for handling. Pretty much a universal one there
All these general statements are true. But let's take a look at the actual impact, on a mathematical basis. Based on factory specs of curb weight 4180#, wheel base 116", Front/rear weight distribution 55.48%/44.52%, I did a "Sum of the moments" calculation: moving the rear axle .75" rearward will shift the weight distribution by only 12#. This will change the ratio to 55.77%/44.23%, a shift of only 0.29%. I don't know if this would be noticable, even on the autocross. This would have about the same impact as putting a set of decent speakers in the front doors, adding the chrome fuel rail covers, three guages to the A-pillar, a cell phone, toll change, some CD's and a Big Mac in the glove box. Switching to Aluminum heads or moving the battery to the trunk would reverse this "damage" 3 times over.
The spring/shock angle change is also miniscule. Assuming a spring height of roughly 12", a lateral change of .75" will change the spring and shock angle by only 3.6 degrees, and the ride height only .02". I don't know if this will have a noticable effect on anything.
The change in wheelbase is 0.65%. Noticeable? You wouldn't think so.
Conclusion: Unless my numbers are whack, if you want to spend the money to move the axle back (correctly), go for it, unless you are trying to get that last .1 second off your time at the track.