What can you tell me about drafting?

[California98Civic]

Hucho's "Aerodynamics of Road Vehicles" is a classic textbook folks on this forum often cite as an authority. Attached photos are of a few charts from the section on convoy driving. I took these shots, but I don't have the book in front of me so I have to tell you the argument from memory. The gist is that really close is not as good for road vehicles as it is for race cars, which are higher drag vehicles to begin with because of the downforce racing teams want. For road vehicles, driving within large groupings of cars (convoy) or at more of a distance (not bumper-hugging deadliness) is better for drag. Anyone care to correct me? That's my read.

[paulu]

Originally Posted by brucey

1 car length for every 10 mph, double that at night or rain, is how I was taught to drive. I never break this rule (unless someone cuts in front of me, then I just slow down again)

I was taught that "Only a fool breaks the two second rule"

No matter what the speed you should keep 2 seconds distance between you and the vehicle in front.

Paul

[Fat Charlie]

My idea of a safe distance varies based on conditions. As does my idea of a safe speed, payload, music volume, whatever.

If there's one thing I've learned in this life, it's that blanket rules are universally stupid!

[graydonengineering]

Originally Posted by actwithclarity

It would take 0.123 seconds to travel 10ft at 55mph. However since a truck cannot stop instantly (lol), saying you only have that long to react is kind of dumb. The main concern is you have to be able to decelerate faster than the truck. I know my little geo metro has pretty weak brakes, so if a trucker really slammed on it I don't know if I'd survive that.

Calculate your gap by doing the following:

When the back of the truck/car in front of you passes an object like a road sign, start counting till the front of your car passes the object.

At 10' back on the highway, you can't even begin to count as only .1 second will go by. That is WAAAY to close for anything but a closed race track. There are too many variables on the open road and everyone may have to slam the breaks without warning at any time.

A "safe" following distance per drivers ed is 2 seconds back. I push that a bit to get a better draft down to say, 1 second and only if it is a big rig since they don't stop as fast as passanger cars which adds just a little buffer. I won't get any closer than that. At 55 MPH, you are going 75 feet per second so that is how far back you would be.

At 75MPH you are going 100 feet per second. If you are 100 feet off the back of the next car. That sounds far but you still get a good amount of pull from 1 second back. Any closer than that will put you in a very dangerous position.

Using this method, your gap becomes more and more as you drive faster to give yourself the same amount of time to react reguardless of your speed. Easy way to draft and at the same time keep your risk to a minimum.

[BHarvey]

60 mph is 88 feet per second, or about the full length of a semi.

Youth might react faster if not texting or whatever else.

It might make a difference in mpg, but I will take a long line of sight over mpg anyday.

[slowmover]

The only safe distance behind a big truck is that you can see both port and starboard mirrors on his vehicle. NO EXCEPTIONS.

Ever see those big chunks of rubber tread thrown off of 18-wheeler tires? Ever picked one up? 15 to 30-lbs of steel wire reinforced rubber coming at your windshield at highway speed is Death looking you over.

Quit being stupid.

.

[aporigine]

Until recently I owned a motorcycle, and I developed great respect for those pieces of tire. I found an article, forget where, that described just how badly one of those bits o'debris could mess up one's legs on the days the leather chaps stayed at home. Recently I had occasion to walk along our local two-lane blacktop and took a close look at one of those gnarled bits of rubber with all that jagged stubbly steel "clostridium condominium" along the edges, and the title of the article I'd read came back to me, eliciting a bit of a shiver:

Rubber Knives.

Now I'm high and safe in the cab of my little pickup, but I tend not to draft. In the local hilly terrain, that would get in the way of my drawing max benefit from Gravity's Gift.
cheers apo

[graydonengineering]

Originally Posted by aporigine

Until recently I owned a motorcycle, and I developed great respect for those pieces of tire. I found an article, forget where, that described just how badly one of those bits o'debris could mess up one's legs on the days the leather chaps stayed at home. Recently I had occasion to walk along our local two-lane blacktop and took a close look at one of those gnarled bits of rubber with all that jagged stubbly steel "clostridium condominium" along the edges, and the title of the article I'd read came back to me, eliciting a bit of a shiver:

Rubber Knives.

Now I'm high and safe in the cab of my little pickup, but I tend not to draft. In the local hilly terrain, that would get in the way of my drawing max benefit from Gravity's Gift.
cheers apo

I used to ride a 250cc Honda reflex on the highway as well and i did fear the rubber chunks. A co-worker was headed up to Phoenix on a group ride with no protective gear at all and got knocked completely off his bike by a re-tread at 70 mph! He was in bad shape.

[PaleMelanesian]

http://www.youtube.com/watch?v=rOhgMAOrp0c

[brucey]

That was indeed terrifying, although I wonder why he was recording that truck?