Jawa

Out of curiosity, when you guys talk about "drafting a semi", how close do you need to be to the back of a semi to get some effect?

Siskiyou

I was drafting last weekend and I stayed far enough behind so I didn't get the buffeting from the semi. It's not so close as to be considered tailgating.

massspike

If you can't see the driver-side mirror, you are too close.

acdii

This. When you feel the buffeting, back off a tad, when it stops, maintain that distance. You are in the slipstream of the triuck at that point and will never be tagged for tailgating since there will be plenty of space between you and the truck to stop, unless it hits a brick wall, then you are both screwed.

chimmike

the drafting is incredibly effective. I mean, I saw an increase in mpg better than 50%.....that's pretty solid evidence that aerodynamics are a big factor in towing mpg.

really, though....if you're not comfortable doing it, don't do it for the sake of mpg. Safety is paramount.

I've found once a truck knows you're behind him, you can tag-team. He'll put his signal on when he needs to merge, and you can take the head, merge and hold the lane for him (flash)...he'll appreciate it. Works all the time.

acdii

I have found when in a car, the most effective wind break is a flat bed, with or without a load on it. For some reason it smooths out the air the best. For the most part, the effective distance is roughly 1 3/4 seconds to 2 1/4 seconds between. Anything further back is useless.