Re: Rubbing fenders on a 5k...

[DeWitt Harrison <de@aztek.com>]

At 06:47 PM 4/22/97 -0600, Jeffrey Goggin wrote:
>>For example, fender clearance is particularly tight for the 5k series and made
>>worse by lowering the car (which increases the track dimensions).
>
>I disagree ... unless you move the suspension mounting points, lowering the
>car simply moves the static ride height to a different position on the
>camber curve for that wheel.  If the tire's going to rub, then it will rub
>whenever it reaches that point on camber curve no matter what the static
>ride height of the car is ... I should also point out that tire flex varies
>by wheel diameter/tire width/section height and this does affect how much
>clearance you need to allow.  I've got 8x17s on my 200q, didn't do ANY
>bodywork whatsoever and they don't rub anywhere with 215/45-17 BFG Comp TAs...

Well, maybe some of the guys who have really studied the rear suspension
geometry can help us out here. My own suspension lowering observations
went something like this:
 1. When the rear wheels move up and down, they and all points on their
tires travel along their arcs or camber curves, as you say. This accounts
for the observation that the wheels "tuck" into the wheel wells as the
rear suspension moves toward full bump.
 2. When I put in shorter springs, but before I realigned the rear
suspension, the wheels appeared to be partly "tucked" just
sitting still since they had effectively moved upward along their arcs of
motion an inch or so. I didn't measure this new amount of negative camber.
 3. When the rear suspension was realigned, the tops of the wheels
moved closer to the inside of the rear fenders. I think this is because
the rear hub carrier (upright?) is located by a fixed length link at the
bottom and an adjustable length control link at the top. The upper
link had to become longer to move the camber toward zero and, I
think, moved the top, outside edge of the tire onto a larger radius arc.

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.

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.

DeWitt Harrison   de@aztek.com
Boulder, CO
88 5kcstq