13'6" Trailers not measuring up?

[Safe Trucking]

Howdy,

I measured about 30 trailers last week, all labeled 13'6" by different companies. They were all 13'3" or 13'4" at the rear. Some had a little lip at the rear where it meets the docks. So anyone have any ideas why they don't measure up? Tire wear possibly? Some spring sag? But some had air bags. All states and provinces I know of allow 13'6" in height, so what gives?

[Rev.Vassago]

Tire size, more than likely. I would assume the trailers are running on 22.5 rubber, which is 2" shorter than 24.5 rubber, but the trailer is designed to allow either size to be used.

[Uturn2001]

Another good possibility would be, if they were air ride, that the air bags were not inflated. Of course there could be any number of possibilities.

[allan5oh]

You also have to consider they won't absolutely push it. The front of the trailer is more of a concern then the rear.

Loaded radius from a 22.5LP to a 11r22.5 or a 24.5LP is only half an inch. Going to a full blown 11r24.5 from a 22.5LP is 1.5 inch.

[Karnajj]

Man, it must be nice to have so much extra time on one's hands to waste it on such useless endeavors.

[Rawlco]

Were they hooked to a tractor? with the suspension fully inflated? Loaded? If not you can't take an accurate measurement. TMC's flatbed trailers newer than 2006 will deflate the airbags when the red trailer air supply knob is pulled out.

Even if they were hooked to a tractor each tractor may have a different ride hight also throwing off your measurements.

Now when you find one that comes out to 13'7" then you may complain.

[TruckerChris]

Were they hooked to a tractor? with the suspension fully inflated? Loaded? If not you can't take an accurate measurement. TMC's flatbed trailers newer than 2006 will deflate the airbags when the red trailer air supply knob is pulled out.

Even if they were hooked to a tractor each tractor may have a different ride hight also throwing off your measurements.

Now when you find one that comes out to 13'7" then you may complain.

Yeah, all of Gordons reefers are Air Ride Auto Drops... A bit of pain in the ass when you want to leave the dock. You have to wait for the bags to air up... :evil:

[Safe Trucking]

Interesting thoughts. The tire size seems very likely. But 22.5" to 24.5" only adds another inch (only the side on the ground makes a difference). But it would make sense to leave a little play room.

The trailers I measured were all empty, none were hooked up, and none had dump bags. I measured the rear because the front depends on the landing gear height. And I agree, I hate pulling a trailer with auto dump bags. They always creep away from the docks a few inches. Last one I drove had a tridem with auto dump, and it took forever to fill the bags and release the brakes.

[Part Time Dweller]

If the trailers are dropped when you measured them, you should have also measured the front. If the trailer is dropped high, the back would be lower. The best thing to do is measure the trailer when it is hooked up to your tractor, that is the only measurement that is important.

[Drew10]

I was bored also, and measured the trailer, front, middle and rear. Hooked and aired up.....13'4" straight across the top. I attributed the discrepency to the same as bridge heights. Got a little "buffer" in there. Dont want to tell us drivers the truth. (We might hurt somebody)

[Safe Trucking]

If the trailers are dropped when you measured them, you should have also measured the front. If the trailer is dropped high, the back would be lower. The best thing to do is measure the trailer when it is hooked up to your tractor, that is the only measurement that is important.

Thats a very good point, and could well be it. But I'd also think that you'd need the nose up fairly high to affect something 53 feet down the road. I'll measure again with units hooked up, measure in the middle, and rear again, we'll see if that makes a difference.

I was originally thinking it had something to do with the all the panels or corner posts being of one height, so to save on costs all companies use standard length materials.

[Windwalker]

I was bored also, and measured the trailer, front, middle and rear. Hooked and aired up.....13'4" straight across the top. I attributed the discrepency to the same as bridge heights. Got a little "buffer" in there. Dont want to tell us drivers the truth. (We might hurt somebody)

Fact is, that the trailer company calibrated their rulers in the heat of summer and the trailers you measured were made in the middle of winter which means the rulers were contracted down a bit and read a little shorter than actual... Just like your speedometer. When you say you're running 60 mph, and the cops don't bother you in OH, it's because your actual speed is only 57... The speedometer reads about 3 miles higher than actual speed, and that helps you from getting a ticket. Having the ruler read a little shorter give you a safety factor with overpass clearance... :wink: