Wiggle behind car carrier

[GrandpaKip]

On this trip, we got some minor wiggle when we were behind 2 different car carriers on 95S in Georgia. I’ve never felt this before. Didn’t see it in the mirrors. 65 mph or less. Felt it in my butt. Just a jiggle that quit when I got around one of them. The other was when one passed me and pulled over fairly close. I slowed and increased the distance and it went away.
I am just curious if anyone else has noticed maybe a different air disturbance behind a car carrier.

[Acdii]

You can still take advantage of a semi's wake while still maintaining a safe distance. That buffet zone is the trigger point, when you feel it, back out just until it no longer affects you, now you are in smoother air that comes over the turbulence. While you are no longer pulled by the trucks draft, you can still use the smoother top air over the turbulence. The turbulence creates a bubble, like in the bed of a pickup, and smooth air flows over the top of it, and when you just touch the last roller in the bubble, the air flows right over the vehicle. It's not as efficient as being directly in the trucks wake, but you get the same effect, just at a lower efficiency. Takes practice to get it right, but it does help. I can usually gain 1 MPG towing my TT by doing it and still maintain legal distance. The downside, it requires a lot of concentration to maintain that position, and as soon as someone cuts in front of you, its all lost.

[deltabravo]

Passin Thru wrote:
Watch a Big jet 747 or 777 or A380 when they make contrails. Watch the contrails for a few minutes and you will see the Wake turbulence which is the scientific name for what you felt. It is just air tumbling over the rear of the truck, replacing the space it occupied.

Reminds of The Air Force term called MITO..... Minimal Interval Takeoff.

I witnessed it during a readiness inspection during my days at FAFB, WA.

B-52s and KC-135s were "scrambled" (launched during a simulated wartime exercise.)
They took off very close distance to each other. LOTS of wake turbulence after about the 3rd plane took off.

You can probably search YouTube and see it.

[Passin_Thru]

Watch a Big jet 747 or 777 or A380 when they make contrails. Watch the contrails for a few minutes and you will see the Wake turbulence which is the scientific name for what you felt. It is just air tumbling over the rear of the truck, replacing the space it occupied.

[Jayco254]

I notice that the older trucks with the big radiator in front will move my unit more than the new streamlined trucks, they don't move me at all normally don't know they are around unless I see them in my mirrors or camera.

[drsteve]

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[drsteve]

Jim@HiTek wrote:
In my Class A, back when I needed to save fuel, I'd draft behind big semi's. And to find the sweet spot, I'd approach them from behind and when I felt the substantial wiggle, I'd move up another 12 feet or so. This is the suction zone and I can see my RPMs dropping while I maintain the same speed. I'm drafting in the semi's slip stream just inside the vortex tail. Saves fuel for me, but costs the semi driver's company. So I don't do it very often any more.

So, yeah, I'd expect there to be a disturbance behind a car carrier. But I've tried to draft behind them but the slip stream is too chaotic for that. The best vehicles to draft behind are double semis.

Close enough to draft is likely too close to be seen in the truck mirrors. Also too close to stop if the truck brakes hard. Might even get you a ticket from the local constable.

Bad idea all around.

[goducks10]

My guess is that your Nissan Frontier is a little under weight for the TT you're towing. That makes it more susceptible to wiggle.
Short WB, light truck, 25' 4500+ lbs TT is going to be effected more in adverse conditions. I think the 25' length had more to do with the wiggle than the weight of the TT.

[mgirardo]

GrandpaKip wrote:
On this trip, we got some minor wiggle when we were behind 2 different car carriers on 95S in Georgia. I’ve never felt this before. Didn’t see it in the mirrors. 65 mph or less. Felt it in my butt. Just a jiggle that quit when I got around one of them. The other was when one passed me and pulled over fairly close. I slowed and increased the distance and it went away.
I am just curious if anyone else has noticed maybe a different air disturbance behind a car carrier.

Car carriers do disturb the air differently. However, if you were south of Exit 29 in GA in the right or middle lane, then that was probably your problem. Those two lanes are uneven enough that they would cause our Motorhome to wander without truck traffic. When we still owned our Hybrid TT I pulled off the road to check the anti-sway bars because the HTT was swaying enough that I figured something must be wrong. We had an Equal-i-zer brand WDH system.

Everything was fine. There was little traffic so I tested each lane. When I got in the left lane, no more wiggle. It's just the middle and right lane from exit 29 south to the Florida line. We live off exit 29 and I see travel trailers wiggle a good bit when traveling south. It happened every time we traveled south from home whether towing the HTT or driving the Motorhome.

-Michael

[Quick_trip]

I don't see anything stating 200-300 feet behind?
But I would think, that to start drafting you must get within 50 feet?
50 feet is to close and the trucker will do as another poster put,, the trucker puts his brakes On!
Back off & stay safe!

[jerryjay11]

drsteve wrote:
I used to have a high top conversion van that really wiggled behind semis. The worst ones were those with air deflectors on top of the tractor.

Per AARP the 3 second rule applies though road conditions should be taken into consideration.

Safe Following Distance
Maintain at least a three-second following distance to help avoid dangerous situations.
Locate a fixed point ahead. It can be an overpass, a utility pole or a shadow across the road.
When the vehicle ahead of you passes that fixed point, count to yourself, “one thousand one, one thousand two, one thousand three.” If your vehicle passes the same fixed point when you say “one thousand three,” then you have a three-second safe following distance.
If your vehicle arrives at the fixed point before you reach the count of “one thousand three,” you are too close. Slow down slightly and increase the distance between you and the vehicle ahead.
Recheck against a new fixed point after you have increased your distance. You should be able to finish the count of “one thousand one, one thousand two, one thousand three” before you reach that fixed point.
Caution: Do not focus so intently on the fixed point that you fail to observe the total traffic scene.

I wish more drivers would be considerate enough to apply this rules when I' driving.

[BadgerMcAdams]

Jim@HiTek wrote:

Tyler0215 wrote:
Car carriers create a lot of turbulance just because of the all the different exposed surfaces. Back off or pass.
As far as drafting, Jim, Its is not the way to save fuel. It's illegal for one thing. Also dumb, stupid, crazy, insane, How else can I say it?
A sudden stop and you achieve a zen state. You become one with the semi trailer.

What are you talking about? Illegal to follow a vehicle 200 to 300 feet or more behind? Since when?

200 to 300 feet...no...But if you are close enough to draft (30 to 50 feet) then you are really too close. That is where I think the "illegal" part comes in. Not saying that it truly IS, but in AZ, cops will pull you over for following too close. What the definition of "Too Close" is, I don't know...may be a Law Enforcement judgement call, may be an actual distance.

Back to your regularly scheduled mayhem...

[drsteve]

I used to have a high top conversion van that really wiggled behind semis. The worst ones were those with air deflectors on top of the tractor.

[Jim]

Tyler0215 wrote:
Car carriers create a lot of turbulance just because of the all the different exposed surfaces. Back off or pass.
As far as drafting, Jim, Its is not the way to save fuel. It's illegal for one thing. Also dumb, stupid, crazy, insane, How else can I say it?
A sudden stop and you achieve a zen state. You become one with the semi trailer.

What are you talking about? Illegal to follow a vehicle 200 to 300 feet or more behind? Since when?

[jerryjay11]

No matter what type of big truck is ahead of you there is always air turbulence. Each vehicle will have it's own character. It is a sure warning you are getting too close and best as advised to back off or pass. Or the next time you draft, that trucker to stop you from robbing him of fuel milage will lock up his trailer brakes.