> FWIW the likely cause of the E30's propensity to roll
> is the semi-trailing-arm layout of the rear
> suspension. The roll center of such a design is very
> high compared to a strut or double A-arm design, which
> means that cornering forces tend to lift the body,
> which raises the roll center, which lifts the body
> more, and so on until the center of gravity moves
> outside the tire contact patch and the car rolls.
I can vouch for this. My E21 320i (first-gen BMW 3 series, for you
non-Bimmerheads - the E30 they're referring to is second-gen) has the same
type of geometry. I added the optional rear sway bar for a while, and
enjoyed reduced body roll, but the inside rear wheel spun a lot on tight
turns. I removed the bar for fun runs one day, and despite the additional
body roll the car handled far better WITHOUT it - I could get the power down
where I needed it. Lifting the inner rear wheel is OK for a FWD car
(Golf/Rabbit, Neon, Sentra), but NOT for RWD! In addition, after seeing
some pics that were taken that day, I was absolutely amazed at how much body
roll I had - WITH the rear sway bar! See for yourself at
http://www.channel1.com/users/ka1ult/igor/autoxpic.htm (there's some cool
general action shots too). After seeing this, I wouldn't want to put sticky
tires on this car. It rolls so much I'd be worried about playing "Roll
Over, Beethoven" in the middle of a run.
- Justin
'83 BMW 320i ST
'95 Saturn SC2 ES (more on this new arrival later)
|