Alan Baker
Just a late, quick correction here. I think that would really be 179 ft-sec, not mph? In that case at 1g you're looking at 122mph rather than 179mph. 0.75g would put you at 105mph. I haven't seen any tire data that ran as low as 0.75mu, even for a locked tire. More than likely 0.85 would be a touch more reasonable, but in reality it's probably somewhere in between.
0.85g would put you at 112-113mph to stop to 0 in 500 feet. What really happened depends a lot on how the skid marks really looked. Chances are if the guy was drunk and spun the truck or got it sideways (I didn't read the article), the skidmarks started at a slip angle of maybe 15-20 degrees or so, which does not equate to a very large deceleration at all during that period (only around .25g). You'd only be decelerating in the direction opposite travel at 0.85g for the period of time where the truck was either sideways or all four wheels were locked. For all times at any other slip angle the deceleration would be lower.
If one buttumed he went from 20 degrees to 90 degrees slip nice and steady over the entire spin period before hitting the tree, the average deceleration in the direction of the road would drop from 0.85g to about 0.6g, putting the speed at about 95mph. If he spun past 90 degrees slip angle the speed could have been even lower than that.
Todd Wbutton
