Re: one opinion

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Posted by Ben ( on 15:16:54 04/09/08

In Reply to: Re: one opinion posted by Jeff in CO

The DOT/NHTSA ratings are for stock vehicles. Suburbans genericly have a 3 star rating, out of 5
star (the best rating).

In a single vehicle crash, a vehicle with a rating of:
Five Stars - ««««« Has a risk of rollover of less than 10 percent
Four Stars - «««« Has a risk of rollover between 10 percent and 20 percent
Three Stars - ««« Has a risk of rollover between 20 percent and 30 percent
Two Stars - «« Has a risk of rollover between 30 percent and 40 percent
One Star - « Has a risk of rollover greater than 40 percent

The other things that affect roll over are:

1) CG and that changes with loading. A roof rack will change it a lot if it's stuff with heavy
things. What/where the other things loaded also affects.

2) Tires and wheels. Even tire PSI affects this, as a low PSI tire will have the sidewall bendback
more and roll over the sidewall to further exacerbate the tendency to roll over.

Wheel width and offset (track) has an even larger effect. Why my track is about 10" wider than

3) The suspension also factors. Poor shocks that allow the vehicle to lean easily. Anti-sway bars
married with too low tire pressure exacerbates the tendency.

This picture of a racer shows all of the above in play.

Notice that the inside tire has lifted off the pavement. The outer tire's inside tread rib has
lifted off the pavement. The outside tire outer tread rib is rolling over a bit, but the tire must
have very high PSI, wider rims and of low profile, so the sidewalls are short and stiff. Guessing
that his CG is just below the emblem on the nose.

BUT, Suburbans are not cars, but trucks, which should not be driven like this unless
re-engineering of the suspension and the rest of the vehicle has been done right.

All 8,600 lb GVWR Suburbans sit about 2" higher than 7,200 lb GVWR Suburbans, both in stock form.
Two things does this, in spite of the fact that both has the exact same body. The frame and
suspension are that much bigger.

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