drafting semi's

[fusion210]

I follow the two second rule (counting one one-thousand, two one-thousand) and it still provides a great benefit while being safe. Plus the faster traffic sees the semi truck in front of you and tries to avoid you both.

[Cd]

I tried drafting semis a few times. I had a real eye opener when the truck in front of me ran over a cardboard box.
I didn't see it until it was right in front of my car.

WHAM !!!

I was following at the point that his mirrors were just barely visible at the time.

BTW, He didn't like me there at all. He kept swerving and slowing down.

Not worth my life to save a few pennies ( or even $5 ) in gas !

[d0sitmatr]

Originally Posted by Cd

I tried drafting semis a few times. I had a real eye opener when the truck in front of me ran over a cardboard box.
I didn't see it until it was right in front of my car.

WHAM !!!

I was following at the point that his mirrors were just barely visible at the time.

BTW, He didn't like me there at all. He kept swerving and slowing down.

Not worth my life to save a few pennies ( or even $5 ) in gas !

some of them really dont like people drafting them, if I get behind one like that, I dont stay there and will go around him.
but some dont mind it at all, that is who hope for

@WDB, trust me when I say 85% of cars on the road cannot stop anywhere near as short as a motorcycle can with an experienced rider.
when you get into some of your higher end cars luxury cars, they can stop pretty darn good. yet still I dont think quite as quickly as an experienced rider can. of course, my experience on a bike is mostly of the performance variety (crotch rockets) that are much lighter than you avg harley/goldwing

when my son/family is with me, I tend to follow the 2-3 second rule, but when Im alone I push it and will follow where I need to be to hit that pocket.

[duffremle]

My own experience is that commercial rigs, (especially heavy construction trucks), are much more likely to throw up rocks than other vehicles. Just the potential for a cracked windshield alone is enough to make me not want to do it.

[user removed]

I generally keep 3 stripes between myself and a big rig. That's at least 129 feet of separation and closer to 140 feet. West of my home the speed limit is 70 MPH and if you want to go that speed then you better just drop in behind a drafting leader and that also has the benefit of convincing other drivers to just pass you in the left lane. In fact they will try to block you from passing the truck, which means they mover over earlier rather than climb up your rear end. I have found that this gives me the same mileage at 70 as 55 without a windbreaker ahead of me. It also allows for pulling over to the right if there is some debris in the road. If the trucker gives me any indication he does not like what I am doing then I back off or pass.

Traffic around here is usually heavy and the trade off is much greater attention to what might come under the truck, versus the constant aggressive tailgating passing on the right and general stupidity that seems to be the norm around here. The tandem (dual trailer) rigs also have a reinforcement extends down low where the trailers hitch together. Another good alternative is a bus or motor home.

regards
Mech

[mattbatson]

so I'm hearing some figures like anywhere from 10 to 30% increase in mpg's...
does anyone have any instantaneous evidence...like from a scangauge? Or are these estimates over a tank?
Anybody done any informal testing...say where they would draft a semi, record the mpg's off the scangauge...then change lanes or drop back and getting another reading, etc..?

[euromodder]

Originally Posted by d0sitmatr

ive always drafted larger vehicles, mostly semi's, and not at recommended distances either, as matt stated, if you cant stop faster than a fully loaded, or even an empty, tractor trailer, then there is something wrong with you or your car.

Dunno about the US semis, but European rigs stop in a surprisingly short distance for their size and weight.

I've put up a link to a video between a semi and a VW Transporter van before - the truck stops as fast as the van.
More load on the rig is better, BTW !

as a long time motorcycle enthusiast, its also why you >NEVER< tailgate a bike, because they have about 1/2 the stop distance of you in most situations.

That's a myth.

A mediocre family car (Toyota Avensis) will stop shorter than a sportsbike (Honda CBR900) or SportsTourer (R1150RS + ABS).
The myth has been tested by a local bike magazine years ago, and proven to be untrue.
To the surprise of quite a few bikers.
Add wet roads, lock-up fever, and it gets even worse for the average biker.

The tests weren't done using average riders, but by Belgian bike racing champions instead - Louis Wuyts won the Belgian title 16 times, I'd say he knows how to ride a bike.

In Dutch, but you can see the tables with the results :
Motornet.be
droog = dry
nat = wet
beton = concrete

Distances in meter and speeds in km/uur (km/h)

[euromodder]

Originally Posted by mattbatson

I recently discovered that you can be 50 to 100 ft back and still see a benefit?

I heard mythbusters found a pretty significant increase all the way back to 100ft? Or did i hear wrong?

The effect is there all right.
Obviously, the closer you get the more significant the effect becomes.

You can try it by closing in on one, and see the instant fuel economy improve as you close the gap.

Trucks are limited to 90 kph / 56mph over here (some even down to 85 kph voluntarily by the hauling company), so most cars are faster.
I sometimes hitch on to a semi at a fair distance (so the driver doesn't get annoyed) and stay there.
On occasion, the instant fuel economy readout was over 100mpg @ 52 mph !

I am pretty confident that i can still be safe at 50-100 ft back

Definitely not at the 50' mark.
100' is more like it.

But I too get a lot closer on occasions.

[mattbatson]

Originally Posted by euromodder

The effect is there all right.
Obviously, the closer you get the more significant the effect becomes.

You can try it by closing in on one, and see the instant fuel economy improve as you close the gap.

Trucks are limited to 90 kph / 56mph over here (some even down to 85 kph voluntarily by the hauling company), so most cars are faster.
I sometimes hitch on to a semi at a fair distance (so the driver doesn't get annoyed) and stay there.
On occasion, the instant fuel economy readout was over 100mpg @ 52 mph !



Definitely not at the 50' mark.
100' is more like it.

But I too get a lot closer on occasions.

I used to road race bikes with the CCS here in florida and agree that braking distance isnt any better than a car...

I also stay at a fair distance, as I've had the semi drivers get annoyed at me. If I stay a full semi truck length back, they dont seem to care.
I'm going to research and see if anyone has done any tests at different distances, speeds, etc.

[user removed]

The buffeting you will feel is the vortexes off the sides of the truck. Moving closer will get you out of the vortexes and it depends on the size of your car. You can also see it when it is raining if you use rain-x on your windshield. The drops will normally run almost vertically off your windshield in clean air (no draft). When you get in the draft they go crazy weaving and even going in circles sometimes.

I don't like getting real close, with 100 feet about my minimum. The stripes on US roads are right at 43 feet from beginning to beginning of each individual stripe. When you barely have 3 between you then you are right at 100 feet. Get right at 4 visible and you are at close to 140. Look for trucks with large mud flaps and especially those with the rear section closed at the rear down to about 2 feet off the road.

Best drivers I have seen here are Wal-Mart. Very consistent as a norm with UPS drivers close. Many will actually slowly lose speed climbing a grade and go to a higher speed downhill. This was the type of trucker I found on my summer of 08 trip of 300 miles in my old VX (sold) that got me 68 MPG for 300 miles, even including 2 hours of night driving coming back home. On one stretch there were at least a dozen trucks drafting each other, and I just followed the pack. Other trucks would pass me a pull over in front of me to pick up the group draft, and I let them in, since they were saving a lot more in fuel than myself. Nighttime was much more stressful, constantly keeping a vigil for the inevitable large piece of truck tire in the road, but I never had to swerve off the road.

I'll bet my Maxima would do 40 MPG under the same circumstances, but in mid 2008 the truckers were running 64 MPH average. They have since raised the speed limit to 70MPH on the same stretch of I95 south from DC to Richmond.

regards
Mech