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Old 08-05-2013, 11:39 AM   #23 (permalink)
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Originally Posted by kach22i View Post
(about slipstreaming a semi ... )
That's 5-6 car lengths which is a recommended minimum highway speed spacing, right?

I would have thought a much closer distance would be optimal, as drafting.
Drafting (aerodynamics) - Wikipedia, the free encyclopedia) (link fixed)
This "suction" he talks about must be something different.
I slipsteam semis a lot at a greater distance than GP advices as I apply the 2 seconds rule.
What I find that if I come too close (less than 10 meter) the air becomes very turbulent. That reduces aerodynamic efficiency and increases resistance, so much so that when I leave the car in cruise control mode (which in eco mode responds slow to lowering speeds) makes it lose speed and self corrects the distance.

The benefits from slipstreaming at a distance are small, but noticeable. But low speed is the real winner. Most of all the presence of the semi provides a legit reason to drive slower than the rest of traffic, which is eager to overtake that semi anyway.

Drafting close by would only work if you draft really close, as like on the towhook. Needless to say that is not a safe driving strategy.
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