Drag on truckers when you tail them? - Fuelly Forums

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Old 01-14-2008, 09:26 PM   #1
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Drag on truckers when you tail them?

Out of curiosity, could someone explain exactly how much a toll it puts on truckers mpg when you draft them?
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Old 01-14-2008, 09:53 PM   #2
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Allow me to talk out of my arse for one moment since many of you know more about aerodynamics than me.


I was reading a post by a fellow yaris driver on yarisworld.com. This guy is a much more proficient hypermiler than I am and belongs on cleanmpg.com. Apparently this was a thread about his progress as a hympermiler he made from a year ago and someone had dug it up to comment on it. One of the commenters complained about drafters affecting his mpgs whenever he was driving his big truck.

I thought in Nascar, the drafting car is using the lead to gain speed in the void left by the lead so that he can then "slingshot" himself past the lead at an oportune time? So you're saying it works both ways? (interesing)

What affects drafting for the lead as pros and cons? Does it matter the size of the following vehicle? ie big lead/small trailer means drag, same lead/trailer (vehicle) = more eficiency?

From what that commenter was talking about it seemed like he was sick and tired of drafters, even said something about knowing how to brake in such a way that the lights won't go one anyone drafting could just deal with it.
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Old 01-15-2008, 08:02 AM   #3
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The front vehicle is "breaking wind" (lol) whether there is someone behind or not. The hole punched by the truck is the "draft" that the second, third, ect vehicle take advantage of. Unless you are "bump drafting" (which takes physical contact), the front vehicle does not gain or lose for the most part (as long as you are front to back in a straight line). Once two vehicles get side by side, they both lose efficiency.
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Old 01-15-2008, 09:29 AM   #4
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I had heard that when you get up close to the truck, you extend the size of his vacuum bubble. You get nil wind resistance, but he gets a larger pull on the rear of him.

Your car isn't large enough to have there be a cessation of flow separation, which is what truckers drafting each other and nascar drafting is about. The trucker still has the area of turbulence and vacuum, your car just makes that area larger, and therefore more drag.
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Old 01-15-2008, 11:05 AM   #5
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Kind of depends upon the distance too. I can feel the engine load up on long tracks when someone starts to get into my draft. And there's a point when working together, very closely, you can develop more top speed than you would alone. That can be used as a break-away group or group trying to hunt down a rider or number of riders ahead.
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Old 01-15-2008, 06:18 PM   #6
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I asked a good friend who has been driving trucks for over 40 years, and he said that you cannot feel a thing with a car, or even another truck behind...it is just annoying, mostly from a safety standpoint to the trucker.

His comments were, you would be amazed at how big an object a truck can either pass right over or how much it can breakup just under the trailer before the car behind has a clue that the front of the car is getting ready to be pasted with debris!
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Old 01-15-2008, 06:39 PM   #7
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^ haha good point

I think the trucker who think he had more drag with a drafter may have been having some psychosomatic effects.
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Old 09-25-2008, 04:43 PM   #8
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Sorry to dig up an old thread, but didn't want to start a new one since some info is already in this one.

Seems to be conflicting ideas in here, one says it will help the front driver, one says it hurts, one says no change. Any new information about this? I drive the speed limit on a 2 lane road and there are always people behind me so I've been curious.
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Old 09-25-2008, 05:02 PM   #9
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I know racing at Daytona on a motorcycle, I can feel someone loading up my engine when they get pulled into my draft. Can usually only feel it once you get going about 120.

But usually if we get a group working together, everyone benefits by going faster in a straight line.

But at 120 to 160, there's squared plus the amount of air resistance too. I don't know exactly if it would be detrimental to the front driver. My intuition says a little...maybe...trying to maintain constant speed.
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Old 09-25-2008, 05:57 PM   #10
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Drafting helps both the puller and the drafter. This can be observed in high-speed car races (NASCAR, F1, etc), bicycle racing, and even in lower-speed group bicycling.
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