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Re: Semi-Trailing Arm Next Ralph Nader No No???

To: Mark Sirota <msirota@isc.upenn.edu>
Subject: Re: Semi-Trailing Arm Next Ralph Nader No No???
From: Paul Foster <pfoster@gdi.net>
Date: Mon, 16 Aug 1999 15:56:59 -0400
Mark Sirota wrote:
> 
> Paul Foster wrote:
> > I'm not sure if you can blame semi-trailing arm suspension. The early
> > 911 (til 993??), 914, 924, 928, 944, and 968 all had the same
> > suspension design without many tipovers...
> 
> Nonsense.  I'm not intimately familiar with the 911, 924, 928, 944, or
> 968, but the 914 did not have semi-trailing arms.
> 
> It had true trailing arms.  They run parallel to the car, and their
> pivot was perpendicular to the car.

Well, the 914 may not have, and also the 911 - certainly no air-cooled
expert, but the 924, 944, and 968 certainly use semi-trailing arms.

Paul Foster

> 
> The BMW trailing arms (from the 1600's through E30 chassis) had semi-
> trailing arms, in that the pivot was at 45 degrees to the axis of the
> car.
> 
> I also don't know if this is a primary factor in the rollover rate;
> after all, 2002's and 320i's don't have a high rollover rate.  I think
> it had something to do with the roll rate.  They built up a lot of
> angular momentum in roll, then abruptly hit the bump stops.  The 318i,
> I think, is worse in this respect than its E30 brethren, suggesting
> that suspension settings (spring and roll rates, shock rates, ride
> height) may be significant factors.
> 
> Still, to answer Peter's original question, I think I'd be afraid to
> run any E30 chassis as a combination daily driver/autocrosser, and I
> don't think it has much to do with tire choice or anything like that.
> I'd certainly be inclined to run ridiculous shock and swaybar rates
> in order to minimize roll rate, to minimize the impact on the bump
> stops.  But I scare easy. :-)
> 
> Mark

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