Mythbusters : Drafting video

[JacobAziza]

I asked about tailgaters, and whether or not they hurt your FE.

The lead vehicle benefits from being drafted.
"In car drafting, the lead car is also getting a benefit. Trailing cars fill in the lead car's low-pressure wake, thereby cutting down pressure drag."
The Daytona 500: Flying Without Leaving the Ground | LiveScience

When bike racers are drafting closely, and wheels touch, the back rider goes down.

The reason close drafting is dangerous by bicycle is because if you bump, the front wheel is the first thing to touch, and with no steering damper, the wheel makes a sudden turn you weren't expecting. Same for a motorcycle, but since a car has a bumper, that's really not a fair comparison.

Drafting is a dangerous practice that is not recommended.

Considering 1) there is a minimal speed differential in drafting (and its is differential between vehicles, not absolute speed, that determines impact force), 2) a semi has about 4 times the stopping distance of a car, 3)they tend to drive more steady than your average car driver, and 4) Mythbusters showed there is a benefit as far back as 100ft;
it really doesn't make sense to make a blanket statement that "drafting is dangerous".

Just like with some people claiming it is dangerous to drive slow on the highway (when in fact the opposite is true), danger isn't just about the risk of an accident, but the product of the risk of accident AND how severe that accident would be if it occurred.

However, I never draft anymore. All the semi's around here speed, all of the time. They are supposedly limited to 10mph under the limit for everyone else, but speed limits are kind of a joke.

[MadisonMPG]

Originally Posted by JacobAziza

The lead vehicle benefits from being drafted.
"In car drafting, the lead car is also getting a benefit. Trailing cars fill in the lead car's low-pressure wake, thereby cutting down pressure drag."
The Daytona 500: Flying Without Leaving the Ground | LiveScience



The reason close drafting is dangerous by bicycle is because if you bump, the front wheel is the first thing to touch, and with no steering damper, the wheel makes a sudden turn you weren't expecting. Same for a motorcycle, but since a car has a bumper, that's really not a fair comparison.



Considering 1) there is a minimal speed differential in drafting (and its is differential between vehicles, not absolute speed, that determines impact force), 2) a semi has about 4 times the stopping distance of a car, 3)they tend to drive more steady than your average car driver, and 4) Mythbusters showed there is a benefit as far back as 100ft;
it really doesn't make sense to make a blanket statement that "drafting is dangerous".

Just like with some people claiming it is dangerous to drive slow on the highway (when in fact the opposite is true), danger isn't just about the risk of an accident, but the product of the risk of accident AND how severe that accident would be if it occurred.

However, I never draft anymore. All the semi's around here speed, all of the time. They are supposedly limited to 10mph under the limit for everyone else, but speed limits are kind of a joke.

I like you.

[JacobAziza]

Thanks!

[Silveredwings]

Originally Posted by JacobAziza

The lead vehicle benefits from being drafted.
"In car drafting, the lead car is also getting a benefit. Trailing cars fill in the lead car's low-pressure wake, thereby cutting down pressure drag."
The Daytona 500: Flying Without Leaving the Ground | LiveScience

That and...

"The decrease in work for the lead car is substantial," Hill said.

I've thought that for a long time. The drafting vehicle is providing a kind of rolling boat tail for the lead vehicle.

I wonder why truckers object so violently to being drafted. I doubt it's because of an altruistic concern for car drivers' safety. Is it because they begrudge the economy realized by the cars, or is it just the ignorant belief that that such economy is at the truckers' expense?

[JacobAziza]

I've never experienced a trucker objecting to being drafted.

They do it with each other all the time out on the open road.
They flash the lights to let the passing truck know the moment its safe to pull in front of them, presumably so the drafting affect is at a maximum.
I took to doing that when I drove my RV across the country, and they would pull in a few feet ahead of me, then flash the running lights a couple times as a way of saying "thanks" (I know that's what it meant, because I asked about it over the CB).

Maybe some people in small cars drive recklessly, (like in Fast and Furious, where the sport cars drive underneath the semis!) and they prefer they just stay away from them all together?

[Frank Lee]

I had one go bananas on me... same trip that I drafted that horse trailer on. Eh hole went on the shoulder and locked up his trailer brakes, throwing lots of gravel. Gotta hand it to him, that was pretty good. But I stayed back there and eventually he came to a complete stop right in the middle of the road! LMAO! I stopped too but eventually took off.

[blueflame]

I have been sprayed with stones here in NZ too. I suppose I might be inclined to do the same. Little blowfly buzzing around my butt.

Its like someone standing too close to you. Its about standardised distances. If you go to another country or sometimes even another town everyone drives different.

On my scooter I nip in and out, travel past cars on the inside etc etc and people totally freak out!

In asian cities I would be called Mr Careful. Here I'm Mr Dangerous.

Usually 30 years plus males in large cars are the most offended.

[tasdrouille]

Around here they let you be most of the time. I just make sure I can always keep eye contact with one of the truck side mirrors.

When traveling in the NE states, I've noticed a bigger propensity for truckers not liking being drafted, but that might not be representative.

[vielecustoms]

I got in "the bubble" undetected by the driver (I'm pretty sure) and hung out in there for a looooong time (150 miles at 75 mph!). I noticed that when I pulled in real close- maybe not 2 feet but... let's just say not far from that- I had to back off the throttle some and the temp gauge suddenly shot up. Bike had no windshield and I had my visor up- amazingly calm back there

this makes since. my father and I drive semi trucks. and i remember being told that the bull haulers have a small section in the front of the trailer blocked off because the truck part would push the air out of the way, and inside the very front of the trailer the turbulence would create a vacuum bubble behind the sleeper and a few feet in the trailer at highway speeds. and the animals would pass out from lack of oxygen! that may be a bs trucker story i have yet to find facts on that, but I do remember trash cans are easily sucked from the side of the road if you get the rear of the trailer just right

I think the main reason truckers don't like people back there is because you cannot see them for like 200 feet behind the trailer. you have to manage the space around the truck because if an emergency comes up you will need to know the best way out without killing someone. also a light rear end car to car will result in some broken plastic and hurt feelings, that same accident with the rear of the trailer there is heaver damage to the car and greater chance of injury. and insurance company's almost always find a way to blame the truck driver.

[Old Mechanic]

I have seen a dozen big rigs sharing drafting duty (less than 75 feet separation) on I95 going south of DC for 70 miles. They didn't like me being between them (costing them money) but following up in the rear at a stopping distance gap was good for 68 MPG in my stock 94 VX, averaging 65 MPH (speed limit), when gas was $4 a gallon last summer.
Another advantage is the rest of the nuts going 80 MPH (reckless driving conviction here), would not think of using the distance in front of me for passing with a few rare exceptions.

I generally like 3 stripes between me and the host (43 feet from point to point between stripes). Since I am a slow (relative to others) driver, the right lane is where I am legally supposed to be. It also gives me an always available escape route to the right if I spot a large chuck of debris, and the time to see the debris.

regards
Mech