Read all about it here:
http://www.nhtsa.dot.gov/cars/rules/rulings/Rollover/Index.html
The abridged version of the report is that after mucho testing they found
that dynamic on track testing did not provide any more data than simple
metric calculations. The calculation they have so far settled on is The
Static Stability Factor (SSF) which is simply one half the track width, t,
divided by h, the height of the center of gravity above the road. This is
proposed to be represented on window stickers and/or product literature in
the format of 5 stars:
" This estimate of rollovers per single-vehicle crash represents the risk of
rollover given a single-vehicle crash:
Estimated rollovers per single-vehicle crash = 13.25 * e(-3.3731 *
SSF).
The computation of SSF at meaningful increments of estimated rollover
risk, using this equation, offers a basis for a star rating. The risk of
rollover indicated by the star rating
pertains to the likelihood of rollover in the event of a single vehicle
crash of sufficient severity to cause a police report. It broadly estimates
the risk, per event, of a single vehicle crash
becoming a rollover; it is not a measure of the risk of rollover over the
life of the vehicle. We are defining the rating intervals as follows:
ONE STAR (): Risk of Rollover 40 percent or greater is associated with SSF
1.04 or less.
TWO STARS (): Risk of Rollover greater than 30 percent but less than 40
percent is associated with SSF 1.05 to 1.12.
THREE STARS (): Risk of Rollover greater than 20 percent but less than 30
percent is associated with SSF 1.13 to 1.24.
FOUR STARS (): Risk of Rollover greater than 10 percent but less than 20
percent is associated with SSF 1.25 to 1.44.
FIVE STARS (): Risk of Rollover less than 10 percent is associated with SSF
1.45 or more.
The relationship between SSF and rollovers per single vehicle crash
which is reflected in the star ratings above was derived by the statistical
method described in the Appendix to
best estimate the national trend between rollover risk and SSF. The
relationship appears to be constant over the four years of state crash data
analyzed, but the agency intends to continue
to monitor it as newer crash data becomes available. Should changes in road
conditions, demographics, or vehicles alter the relationship, the levels of
risk associated with the star ratings
would be adjusted."
It would be fun to rate the vehicles Kevin put forward with the system
listed above, but it requires CG height data, which us bench racers don't
have easy access to...
-Carl
> -----Original Message-----
> From: Darren P. Madams [mailto:darren@madams.com]
> Sent: Wednesday, October 18, 2000 1:17 PM
> To: ba-autox@autox.team.net
> Subject: Re: Vehicle eligibility...
>
>
> Ok, I'll bite... damnit... :)
>
> Isn't there a better way to predict rollover stability?
> Didn't this come
> up when that idiot at the insurance department or something
> used a formula
> similar to Kevin's numbers comparison (sorry Kevin, not a jab
> at you) and
> came to the conclusion that any SUV has a 95% chance of rolling over?
>
> It was disputed that even the height of the CofG does not have a
> substantial effect on rollover probability. I think it was
> also discussed
> on the national list that rear suspension and shock function
> at full (and
> over) compression and full extension contribute to a large portion of
> rollovers. I would think it would have to do more with roll
> centers and
> polar movement and inertia than just track/height.
>
> Now, whether you want to make that a requirement for vehicle
> eligibility is
> up for debate... and what other cars might be excluded
> (Larry's Focus? BMW
> 318ti's?) too...
>
> --D
>
> p.s. I wouldn't allow the Previa to run just on the "why push
> our luck"
> common sense rule, but you're right in that there's no
> specific rule. I
> don't have my rulebook handy but I'm sure there's an out for
> the Safety
> Steward or Solo Chief to override anything in the name of safety. Of
> course, then the action is protestable, but a PC will most
> likely agree
> with the chiefs.
>
> At 12:31 PM 10/18/00, Kevin Stevens wrote:
> > >A Previa is not an acceptable vehicle for Solo II.
> > >
> > >--John Kelly
> >
> >(paraphrased: "Ditto." -- Charlie Davis)
> >
> >I'm wondering about the grounds for these opinions? I don't
> particularly
> >care about the Previa, but let's look at it.
> >
> >What the (1999) rulebook says:
> >
> >=========================
> >3.1 ELIGIBLE VEHICLES
> >A Solo II Event is open to any vehicle that can pass safety
> inspection...
> >except that vehicles with wheelbases exceeding 116 inches
> may be excluded...
> >
> >Unstable vehicles with a high center of gravity and a narrow
> track must be
> >excluded (e.g. Suzuki Samurai, Jeep CJ series, and GEO Sidekick).
> >==========================
> >
> >Vehicle Track Height
> >Samurai 51.4 65.6
> >Wrangler 58.0 70.6
> >Sidekick 55.x 64.3
> >Previa 61.4 68.7
> >Camaro 60.6 51.8
> >
> >Clearly the Previa doesn't have a narrow track compared to
> anything. High
> >CG would have to be measured; however of note is that each
> of the exampled
> >vehicles are taller than they are wide. The Previa is two
> inches wider than
> >tall. It also carries its engine and drivetrain
> significantly lower than
> >most vehicles. Its wheelbase is 112.8 inches, the 4x4s
> range from 80-93.4.
> >
> >If we intend to exclude all minivans and SUVs, we better say so - the
> >rulebook quite carefully does not. If there's some more
> subjective criteria
> >y'all are using, what is it? I don't have enough experience
> with non-coupe
> >cars in autocross to have a valid opinion - I never see them run.
> >
> >KeS
>
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