Subject: Re: Opinions on 96 Blazer and Bravada wanted
From: jschaefe@genesee.freenet.org (John W. Schaefer)
Date: Jan 23 1996
Newsgroups: rec.autos.4x4

In article <4dnlfh$p8v@zoom2.telepath.com>, michael@intellisys.net says...

>...GM's idiotic decision to release a redesigned vehicle
>without adding dual airbags...
>
>The Chevy and the Jimmy are the same except for trim/options
>differences.  The Bravada is the same except for drivetrain and...

>They are all nice looking vehicles, but I decided it does'nt matter
>how good they look if you're not around to look at them.  I'm buying a
>Ford Explorer for the safety of my family, they rate much better in
>the crash tests.

	Sometimes corporate market planning screws up. I reckon GM regrets 
the Blazer/Jimmy/Bravada airbag decision big-time, especially in light of the 
recent go-ahead on a suit against Ford for crash injuries suffered in a 
vehicle that was made before any air bags were mandated. The extension to 
injuries suffered by passengers now is obvious. But life is full of mistakes.

	Personally, I reckon that I have quite a bit of control over whether 
I hit anything, or anything hits me, via the front of my Jimmy. I have much 
less control over being T-boned, so that's where I would especially value 
extra protection provided by the vehicle, but no production SUV yet offers 
side impact airbags.

	With regard to that personal control over front impacts, I wanted 
very much to buy an Explorer, early in my search. An uncle of mine is a 
retired Ford corporate vice-president, and I could have gotten a deal. But 
the extraordinarily low front and rear lateral suspension resonance 
frequencies made me decide otherwise. Under impulse excitation--sudden 
steering input while at speed, such as an emergency evasive manuever--the 
Explorer takes at least twice as long as do the Blazer/Jimmy/Bravada to load 
up the suspension and begin to apply lateral force to the suspended body 
mass, meaning that the peak lateral speed differential between the 
contact patches and body mass will be much greater, meaning a whole lot more 
peak lifting force on the inside wheels. Skids start with peak lifting force, 
not average force, because sliding contact-patch friction is so much less 
stable than static or creeping friction.

	In idealized skidpad testing with gradual loading, the body lean 
angles and maximum turning G forces may be comparable, but real life 
emergency evasive driving always requires quick turns that create impulsive, 
not gradual loading. Even cone courses are unrealistic when driven by 
experts, because they intuitively compensate for the suspension windup by 
applying the steering excitation shifted forward in time from the desired 
result. Normal drivers don't have that skill, and besides the basic 
nature of on-the-road emergency driving is that you can't anticipate 
it--if you could, you'd get out of the way a lot sooner and more 
gradually.

	The evasive behavior of the Explorers I drove reminded me of a 1965 
Buick convertible my parents once owned, or maybe of an old shallow-V 
Chriscraft inboard. I feel much safer in that regard in my Jimmy. 

	Vehicle safety is complicated. You have to choose what parameters you 
want to optimize; some vehicles are better at some things, others at other 
things.
                                           John Schaefer