BBB5S4 Dave

I may be slow or something, but this only occurred to me for the first time.

At the front end of the car, under compression, you will add negative camber, and in rebound, positive camber. As a result, during cornering as you transfer load, the camber dynamically changes in a "good" way in order to maximize the tire's contact patch.

However, I wonder if this dynamic camber is "optimized" to the roll-resistance of the stock suspension setup? Also, it may be interesting to see how this interacts with caster.

ryans4

...which is nearly identical to a B5 A4/S4 front.

Front camber gain/loss relative to ride height on a stock A6 2.7t (positive numbers are a gain in negative camber from spec., negative numbers are a loss in negative camber from spec.)
<img src="http://www.stasisengineering.com/images/multilink_q_camber_gain.jpg">


Front bump steer +/- Toe change relative to ride height on a stock A6 2.7t
<img src="http://www.stasisengineering.com/images/multilink_q_bump_steer.jpg">


So this gives you a good idea what the net affect is when lowering the car relative to geometry changes from stock height. So if you plug in an assumed stock ride height similar to the A6 2.7t (which is higher, but not by that much) and you figure an OEM spec. alignment at -.7 degrees of camber up front and a 1/16 or so Toe In, you'll see what the changes are.

allegro

how is the optimum ride height calculated?

ryans4

...period.

Unless you run no bump stops and you modified your upper fender well to allow the trailing upper control arm to pass up and through the fender, then you are going to run out of bump travel from the physical suspension before you jam the damper into the upper mount.

Or on the other hand, you run a longer spring that coil binds before the prior paragraph happens, which I don't know anyone doing.

As for bump travel, you'd want enough to handle normal loads, and accept bump stop contact under extreme non-cornering loads. So figure in the motion ratio of the S4 front (which is not linear in damper to wheel travel), and then figure back your max wheel movement.

So say you need 3" of wheel bump travel, and maybe 8" of rebound travel, that translates to about 2" of damper travel prior to hitting the bump stops and about 5 1/2" of droop travel, which may be a bit of an exaggeration, but not that far off.

So now lower your car till you have 2" of bump travel (or even more simply, you can see 2" of shaft on the damper), raise it back up and see how much droop travel you have, which should come into about 5" or so.

Or, figure you need to be around 25 1/2" fender to ground assuming a normal 225x45x17 tire on the OEM wheels.

Funkweasel

Great info. ygm btw.

ryans4

i live and die suspensions, so the rest of you don't have to...

Cup-a-Chow

and I seriously need to get my act together and get this ghetto-slammed *** car back up to a real ride height so that the car can actually handle well! Know anyone with 2000 perches FS?

Waseem // TMK

my car feels better lower than 25 1/2"

i completely agree on one point... I need
more suspension travel (dunno how low the car is, but it's low)

i had the car at 25 1/2" at each corner for
awhile... didn't like it. didn't feel like
the car handled worse when i lowered the car
more... in fact, it seems to have the opposite
effect... but i'm not a pro driver... so what do i know...

Singletrack

Thanks man.

MichaelTM

how do the numbers (2 inches bump, 5 1/2 rebound) translate into 25 1/2 fender to ground?