Tip #7 Air Gap

Welcome back. We’re working on improving your fuel mileage. How are you doing so far? Tip #7 is another factor that has a big affect on your fuel mileage and won’t cost you anything to fix. It’s called air gap. Air gap is the space between the back of your tractor and the front of your trailer. Right now we are talking about van type trailers. Whether it’s a dry van or a reefer it’s the same thing. Ideally it should be eighteen inches or less. If it’s bigger than eighteen inches, the air rushes into that space while you are driving and creates drag. No matter how close your trailer is to your tractor, some air is going to get in there. We’re trying to reduce it to a point that improves that fuel mileage. We don’t want it too close though because if it is you are going to run into problems with the trailer coming in contact with your tractor during tight turns. That won’t look good on your resume.
Measure the space with your rig in a straight line. If it’s more than eighteen inches, you will need to slide your 5th wheel in order to close up the space. For anyone who has not slid their 5th wheel, there is a switch on your dashboard to release the pins on either side of the 5th wheel. Once the pins are released you slide the 5th wheel the same way you would slide your tandems when scaling your load. Release your tractor brakes while leaving your trailer brakes on. If you have not moved the 5th wheel in some time the pins may not release easily. You may have to squirt some WD-40 or similar substance around the pins and into their holes and then rock forward and back a bit until they release. If after doing this the pins still don’t release, the switch on the dashboard may be bad. I had to replace mine recently. If the switch is OK there may be a problem with the air line (possibly kinked) or the cylinder that actuates the pins. Your mechanic can help you with that. Incidentally, once I moved my 5th wheel to accomplish the eighteen inch gap, I have always been able to get any load legally scaled by moving just my tandems.
For those of you that might not have a sliding 5th wheel, the process is a bit harder but the principle remains the same. If you can’t move the 5th wheel at all, you may want to look at extending the back of your tractor with some type of extension that attaches to the back of your sleeper.
Remember, you will lose 1% of your fuel mileage for every inch over 24 inches on that air gap.
That’s it for now. Little by little we should be improving on your fuel mileage. The good news is that we haven’t had to spend any money yet. There are still more tips to come that are free. Stay tuned. Until next time, be safe out there.

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