Re: Rubbing fenders on a 5k...

[AUDIDUDI@delphi.com]

> It's my belief that this adjustment effectively moved the rear wheels
> outward, away from each other, and therefore increased the track
> of the car.  I'm sorry I did not actually think to measure this.

The track width hasn't changed (well, perhaps slightly but not more than a
fraction of a millimeter or so) but the wheel camber certainly has.  

Since most suspension systems are designed to have negative camber gain in
bump (i.e., they go more negative when the wheel moves upward and positive
when it moves downward thus helping keep the tires flat on the ground when
cornering), lowering the car generally increases the static camber setting
thereby increasing wear on the tire's inner edges.  Since most people find
this unacceptable for normal street use, the extra camber's often adjusted
out.  For racing, though, exactly the opposite is true and extra camber is
often added ... look closely at how much camber the SuperTouring cars will
run at some tracks, especially the BMWs.

> There do seem to be personal experiences which both contradict
> and support my theory.  Some guys say they run 225/50R16
> rubber on 8" rims and 35 mm offsets with no sweat, while others
> can barely fit 205/55R16s on 7" rims with a stock offset.  Some
> of it may have to do with the degree of suspension lowering but,
> other than that, I really have no explanation for the apparent variation.

Two points here: 1) Like it or not, but there are production tolerances for
bodywork just as there are for every other part on the car; and 2) when you
use larger diamter wheels, you often avoid clearance problems.  In my case,
I guarantee that an 8x15 wheel with 45mm offset will hit the rear shock but
my 8x17 with the same offset won't ... also, some brands of tires differ in
actual size despite having the same nominal dimensions.  Check out my ASCII
art for a clarification about how wheel diameter affects clearance...

            
    17" ->  [________]/ /    
    15" ->  [________] /<- See how the 15" wheel hits the strut and the 
                I   / /    17" wheel doesn't despite having the same
                I  / /     overall diameter?       
                I / /
                I/ /
                Il l



     _             _             
    / l       l o l  \       l o   Jeffrey Goggin
   /__l l l / l l l  l l l / l l   AudiDudi@delphi.com
  /   l l_l \_l l l__/ l_l \_l l   http://people.delphi.com/AudiDudi