Hi Lars-ss:
Quote:
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Originally Posted by lars-ss
Are you implying that driving 70 + miles per hour in a modern car is unsafe? Or just with overinflated tires? I would never put my kids in danger unnecessarily. But when you are driving on a freeway trip of 14 hours plus and you are accomplishing it in one day and the speed limits are 75 miles per hour on the Interstate, you do what you have to do.
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___I am not saying over-inflated tires are un-safe at all.
___The proof of higher speeds being less safe can be proven with simple physics … Besides the increased emissions, increased fuel consumption, higher wear and tear by traveling at higher speeds, there is the safety issue.
Reaction Distance = Reaction Time * Speed
Speed is ~ constant during this period because you haven’t touched the brakes yet but you might have slightly pulled your foot from the accelerator? Perception + Reaction time = ~ 1.5 seconds for most.
Braking Distance = [(Initial Speed (ft/s))**2]/(2* Deceleration)
Deceleration is ~ constant during the severe deceleration phase at ~ 30 ft/Sec**2 using C&D’s 70 - 0 miles per hour braking distance of 181 ft for our Little Beauty’s. This was from
C&D’s January 2000 Insight Road Test.
88 ft/sec = 60 mi/hr.
Reaction distance + Braking distance = Total distance traveled before stopping.
At 50 miles per hour: Total braking distance = 110’ + 90’ = 200’
At 75 miles per hour: Total braking distance = 165’ + 202’ = 365’
___That is > ˝ a football field longer to stop from 75 miles per hour!
___So two things … Would you rather hit something at 50 miles per hour or less (
or possibly not at all!) given you might actually have time for some braking or accident avoidance steering correction in any distance > 110’ before the collision or at 75 miles per hour where you have probably already collided with whatever (165’ or less) before you had the chance to touch the brakes or make a correction? Remember that your perception + reaction + actual braking time at 75 is almost ˝ a football field longer then at 50 miles per hour. I am not even including the damaging impact energy that has to be dissipated! How many accidents could be avoided with that extra ˝ football field of distance anyway?
___Someone else can check my math from the following:
http://www.sci-ed-ga.org/modules/dri...stigation2.pdf
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
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Waynegerdes@earthlink.net