semi drafting

RodneyWright · **Posted:** Mon Sep 15, 2008 1:22 pm

While driving back on I95 to Raleigh from Laurinburg, I decided to test the drafting of large truck vs SUV vs open air. The bimmer has a MPG function, so I cleared it when I hit 95. I was in open air as much as I could be and after 15 miles or so with the trailer in tow, I was hitting about 25 mpg. At that time I was running about 72. I came up on a transfer truck that was running about 68, so about a 4 mph drop and not a drastic change in speed.

I reset the mpg function and tried to stay about 3-4 car lengths back. I was surprised as the mpg gauge started to rise. After about another 15 miles it averaged out to about 29.5 mpg, so that’s about a ~18% increase in mileage, not too shabby! After that I fell in behind a Ford Exploder and in keeping my same distance, I reset the meter. This time mileage fell to about 28mpg, so about a ~12% increase in mileage.

So, there is validity in drafting a larger truck. The big suck factor in drafting a semi is you get “billboarded” and can’t see what’s ahead and that started to wear on me as I was tired of seeing the big “Penn’s Finest” seed logo. If you can stand to follow someone and draft, it stands to save you some bucks down the road.

Richard Casto · **Posted:** Mon Sep 15, 2008 2:26 pm

They did this on Mythbusters IIRC. My biggest concern is, as you mention, you can't see what is going on further down the road. I really like to see what is happening at least 2-3 cars in front of me when in traffic.

RobLupella · **Posted:** Mon Sep 15, 2008 3:03 pm

Ahhh so you were the guy tailgating me that I brake checked :wink:

Vincent Keene · **Posted:** Mon Sep 15, 2008 4:09 pm

Ask Graham what he thinks of the idea Rodney. There is way more to be lost than gained using this practice.

Dustin Fredrickson · **Posted:** Mon Sep 15, 2008 11:56 pm

Vincent Keene wrote:

Ask Graham what he thinks of the idea Rodney. There is way more to be lost than gained using this practice.

Agreed 150%. I'll pay the extra gas, thanks.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Vincent Keene wrote:

Ask Graham what he thinks of the idea Rodney. There is way more to be lost than gained using this practice.

Except Graham wasn't drafting a semi. The road in front of me was clear. I was 5 lanes over from that semi. His shit came apart and traveled 5 lanes to visit me. Since I never really posted this cause I just didn't feel up for it.

In mid-Feb I was 7 weeks post back surgery. On my way to see my back surgeon to get cleared to start PT and work my way back to 100%. I was traveling on I85 past Burlington. I was in the very outside passing lane. He was on the inside lane. The rear axle of his truck came apart. One set of rear wheels. As in the 2 wheels stuck together and the hub that holds them (not just a tire). Flew across the highway and took out my car. I never saw them coming and never saw them leave. The DOT found the things the next day. They rolled down the road up a large embankment and tried to cross the road to a shopping mall. Fortunately they got tripped up and hung on a fence.

The wheels hit my Z06 in the front right quarter right by the wheel. Car was a total after I made a stink with the insurance company. The frame was bent. The A-arms, shock, sway bar link, mounting, were either bent, twisted or snapped completely. The font wheel just got flattened. Hood, nose clip, pop up light, quarter panel, door panel, computer, wiring AC unit were all smashed. Other random stuff in the engine bay. The air bags deployed. So also add interior work. The estimate was over 1/2 the value of the car and on its way to 2/3.

When the air bags deployed I couldn't see shit but big white clouds. And couldn't breath because all the damned talcum powder was all over the place. I slid the car blind and managed to get it over to the right hand breakdown lane. Fortunately did not get creamed by any cars behind me while in a power slide. No brakes and almost zero steering. AX and DE training does pay.

As for me. Well being post-op and fighting with a tractor trailer. I lost. The impact was so hard it knocked the hell out of me. It felt like I got hit by a wall that was moving at me. The impact shook me for 3 days. The disc in my back is not happy. The previous surgery became a wash. My nerve pain came back with a vengeance. I've been going through rehab for all this mess since and trying to get me back together. It's sucked.

If drafting a tractor trailer sets you up for a blind sided hit. Don't. Trust me on this one. It hurts more than you think.

Graham

Kevin Allen · **Joined:** Thu Aug 28, 2003 6:42 pm **Posts:** 3479

Wow. It's a good thing you had a roll cage... :leave:

Richard Casto · **Posted:** Tue Sep 16, 2008 7:57 am

Graham,

Sorry to hear about this. I had not heard the details.

Richard

Stacy King · **Posted:** Tue Sep 16, 2008 8:14 am

So Rodney... did you try the open air at the two different speeds? 72 vs 68?

And at what speed were you following the SUV?

Bernie Baake · **Posted:** Tue Sep 16, 2008 8:28 am

Good grief, Graham, I can't believe that the Ins Co gave you any hassel about that car. Mine was totaled by Rick Hendricks collision center, and the estimator never left the building. He simply looked out of the window and said it's totaled. If you approached the car from any side other than the drivers side you'd have been hard pressed to tell it was even in an accident.Get hooked up with Cline Hall for ins. they'll even pay for bad track experiences, ONCE.

RodneyWright · **Posted:** Tue Sep 16, 2008 10:10 am

Stacy King wrote:

So Rodney... did you try the open air at the two different speeds? 72 vs 68?

And at what speed were you following the SUV?

Followed the SUV at ~70. Did not baseline open air at 68.

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