View Full Version : Drafted by an 18-Wheeler

02-02-2013, 05:02 AM
Driving East in cruise (65 mph indicated) today on I-40 on the flat between Little Rock and Memphis into a light easterly wind we got into a situation where a Freightliner Cascadia would creep up behind us nearly into our tailpipe, pull out to pass and then drop back. This happened about 5 times before I figured out that my wind shadow was affecting his speed and that when he got out of it he couldn't maintain enough speed to pass. Never had that happen to me before (always looked at an 18-wheeler as a draft provider) and it shows just how much air the Sprinter carries along with it at highway speeds. When it dawned on me, I kicked the cruise up a notch to get far enough ahead so he wouldn't have to keep pulling out.

02-02-2013, 05:31 AM
Was this a Sprinter based RV or one of the big Freightliner Class A chassis with big RV body with lots of slideouts?
Very interesting! Most of the big Cascadia's have Detroits or Cats in them and I would think they could get right on by.
Used to get the same effect with my MF 4x4 Box Truck and trailer.
I could get going enough to get all the way up to the tractor on the big 18 wheelers, but the "wind wake" of the cab and roof spoiler would
stop me with my cab even with the back of the sleeper.
Very frustrating and I finally figured out that I could only pass them going downhill.
The Mitsubishi Fuso 4x4 could pass them all day @ 60-65 MPH, but once they got past 65.... it was hopeless unless downhill.
The Mitsu was a 5 speed granny low and just didn't have a gear to shift down to like a Sprinter.

02-02-2013, 01:54 PM
Interesting. I've suspected this was happening for a long time now. I would notice that big rigs would pull in behind me and keep pace with me. I'd move to let them have a straight shot thinking they wanted to fly by but they would slow down. Or, I'd slow down to let them pass and they would rather slow down too. This would go on for many many miles. I think the Sprinter high roof shape makes a pretty nice air cutting tool for them to save fuel costs.

02-02-2013, 02:27 PM
Was this a Sprinter based RV or one of the big Freightliner Class A chassis with big RV body with lots of slideouts?
Very interesting! Most of the big Cascadia's have Detroits or Cats in them and I would think they could get right on by.

Look at my signature for what I'm driving. This particular Cascadia must have been power-limited in some way; probably as a fuel saving feature.

02-02-2013, 02:39 PM
Look at my signature for what I'm driving. This particular Cascadia must have been power-limited in some way; probably as a fuel saving feature.

Mobile devices and their forum apps like Tapatalk do not show user signatures...

Aqua Puttana
02-02-2013, 02:40 PM
... This particular Cascadia must have been power-limited in some way; probably as a fuel saving feature.
Whether it is speed/power limiters or just GPS monitoring it certainly seems that most trucks have slowed down drastically in the past couple years.

Even in my standard roof I've noticed what you said in the first post. I also notice that a strong headwind noticeably affects my mileage. A tailwind helps a bit in a good way, but not as much because the speed delta is so much less.

Interesting thread. vic

Edit: TH43's info in response to OrioN's comment.

'02 316 2500 SHC FTL 140 passenger, NAG1, 3.73 diff, 16" wheels, OM612 w/EGR (>270k mi.), '04 Golf PD-TDI (>110k mi.), both bought new

02-02-2013, 02:54 PM

Here in Ontario all transport trucks are required to have a speed limiter installs as of about 2-4 years ago. They were following suit with a number of there places doing the same thing.

In Ontario there speed is limited to 105km/h or 65mph.

It has reduced some not all of the crazy truck drivers in our neck of the woods so to speak.

02-02-2013, 02:57 PM
For what it's worth, having the semi riding on your tail helps your fuel mileage, too.

Just remember to signal long before you do anything rash...


02-02-2013, 03:06 PM
I know you have a T1N Sprinter!
Many company owned trucks have speed limiters set around 65 mph.
Might be your Cruise Control and the Cascadia's speed limiter where both set the same.
Or the truck driver could be one of the multi million milers that observe speed limits everywhere,
and he did not want to run at a speed that could get him a speeding ticket, even it if was only to
pass a Sprinter.
I used to like to draft quite a bit. Worked great with my Mitsu 4x4. Develop a short term trust relationship
with the trucker by moving into the passing lane and flashing your lights to let them pull out and around slower
traffic in front of him. After a few cycles of this... he/she trusts you and you trust them.
Don't do much drafting with Sprinters as both the T1Ns and the NCV3s get buffeted by the wind wake from
18 wheelers and it's not a pleasant ride especially with a 4.5k lbs. trailer (like in my avatar) on the back.
Sometimes I'll find a short low boy trailer that's empty but pulled by a tractor with a huge sleeper and
aero package. Almost no buffet behind that kind of rig.
The new under trailer aero packages help a little, but regular deck height trailers just jerk a Sprinter around
too much to be comfortable.

Old Crows
02-02-2013, 03:43 PM
Oh yeh! I've had that happen.... big rig or Class A MH gets right behind you. They try to go by and don't have enough moxie (rpm/speed limit, CC, no guts) to drive on by. I just 'beep' the CC down a couple times and let them go by. Then I "beep" it up the same number and keep on going most likely repassing them in a mile or two. Once you get to a slight uphill grade they start losing it and you just motor on. About two times of that foolishness, I just 'beep' it up a time or two and slowly ease away from them to put enough distance between us that they'll have to work really hard to catch up and get by.

Class A's w/ a towed are the the most problematic as I think the drivers have sense of smug arrogance with their big Cat or Cummins powered beasts as they pass a 'mere' B with a Benz star on the back. They usually pass me on a down grade going like a bat out hell and then as their energy decays away on the next hill they begin to slow and you can see the soot starting to bloom out of the exhaust as they try to maintain the speed. Then's the time to strike... the Crow's Nest just grooves on by... and Crow puts on his best evil grin and snickers like 'Muttley'.... Ssssss! Sssssss! Sisssss! No speeding mind you.... just keepin' a steady speed.

I don't get closer than about 3 van lengths (actually I use a 4 second rule) behind a big rig or motor coach (or anything!) due to the extreme buffeting behind them. Portable parking lots and tankers are the worst.

I do love the smooth power the Sprinter puts down..... It is just awesome!

Aside from flashing headlights to let an 18 wheeler it's OK to pull back in.... sometimes they need to get back in quickly... I also pull on the lights when passing them to let them know I'm on their left rear quarter and coming up along side.... just in case they are not looking. And you do develop a relationship with the professional guys and gals.

02-02-2013, 04:12 PM
... you do develop a relationship with the professional guys and gals.

At the top front of the trailers there usually is a spotlight or two for backing in to loading docks. Many truckers flash those as a way of saying "thank you" for something you've done to make their life safer or easier.

I live for those spotlight winks. :hugs:

02-02-2013, 04:35 PM
Old Crows,
Interesting that you find tankers and car haulers have the worst buffet.
I've had pretty much the opposite experience, but from a bad law enforcement
experience when I was much younger I'll stay well off the rear bumper of
tankers hauling flamable fuels.
Food grade oil tankers.....not so much!
Car haulers (I.E. protable parking lots) some are OK.....some are not ....not so much!

Hmmmm...never had them flash the trailer backup lights!
Mostly they will turn the clearance lights off then back on (or flash them a couple of cycles)
to let you know that there was a communication and that they appreciate
your courtesy!
It always amazes me that when I flash the brights/passing lights (at night) or turn the headlights on/off
with the passing lights on the stalk (during the day) as a courtesy to let someone change lanes in front of me, how many regular drivers (not truck drivers) do not seem to understand that I'm feeling safe with letting them in, so go ahead.
They get all flustered, stay in lane, some dart around a bit, do little crazy things.
I was just flashing them to let them know I see their turn signal....we have communicated..
so it's fine to change lanes in front of my Sprinter.

02-02-2013, 10:05 PM
Straying a bit off the original topic now, but into the interesting subject of extra signals with lights.....

UK highway code is quite clear, flashing the headlights should only ever be done as a warning to let another vehicle know you are there, and likewise should always be interpreted as such, reality is quite different!
- Trucks here will generally flash their lights when an overtaking truck gets it's rear end clear of their bumper to let the other driver know he can pull in (seems way too close to me!), a lot of them will do it for the sprinter too and some will even do it for cars. I always try to remember to do it for them when the situation is reversed (when a main road has a reduced speed limit I tend to stick with it, when the limit is 50 most trucks will keep going at 55 or more so this happens more than might be expected)
- Another common use is at junctions etc. to let another driver know you intend to let them pull out in front of you. I get this a lot leaving the industrial estate I work on because I have to make a right (think left if you drive on the wrong side of the road) onto a main road where trucks and buses need to make a right off the main road into the road I want to emerge from, the main road is not that wide so they need to cut the corner, which means they need to stop short of their turn point and let the first car out before they can turn in, they flash their lights to confirm it. This is actually problematic if you follow the rules because you are supposed to interpret that as a warning not to pull out....
- If someone sees a problem with your vehicle they will often flash to let you know something is wrong (check you have your lights on if it's dark), the problem with this is that on some of our bumpy roads the car behind can often appear to be flashing due to change in headlight angle as the car is pitched up and down by the bigger bumps, which can lead to drivers getting paranoid and pulling over to check.
- Certain kinds of drivers, you know the type who drive fast German vehicles or white vans, who don't have any regard for the speed limit have developed a dangerous habit of driving right up close behind a slower vehicle and flashing the lights to intimidate them to move out of the way - often you are already doing 70.
- The last one I can think of for headlights is that having passed a speed trap or police car, some drivers will flash at oncoming traffic for the next mile or so as a warning. This might also be used to warn you of an obstruction or traffic jam coming up, or heading to my parents house for any of sheep, goats, or deer in the road.

The other main light signal used here is after you have let someone pass, or flashed to let them know it's safe to move in, as a thank you signal, after cancelling the turn signal (if they used one) they will flick the stalk one way then the other and then back to centre to give an alternating flash by way of a thank you.

All of the above is non-official and if you were to crash as a result of any of the signals the courts view would be that you should only have interpreted flashed headlights as a warning that the other vehicle was there.

I find it fascinating the way society has found so many ways to intend and interpret a flash of the headlights!

Do you have any different ones in other parts of the world?