TV and 5er Leveling

danrclem wrote:

Harley Doc wrote:


I've been lurking for a while, new to the group, so Hi to everyone. I've been reading these topics for a while (as I am currently not pulling level myself) and wanted to add a comment, or really, make a request. While a 6 inch gap between the trailer overhang and the bed rails seems reasonable, do we have a math whiz or Engineer who could give us a formula to determine exactly how much of a dip in the front wheels would create a 4, 5, 6, 7, 8 inch rise in the tailgate (or rearmost part of the bed rails)? It seems to me it would be a function of the wheelbase compared to the distance from the rear axle to the tailgate. If the front wheels dip X inches (or degrees), with the rear axle as the pivot point, the rear bumper (or top of the tail gate) should rise a corresponding Y inches (or degrees).

While this formula would not be perfect nor take into account compound curves (turning when the front wheel dips or goes over a hump), it would at least give us a baseline for our TV and trailer combination. It seems like longer wheelbase TV's would have an advantage in the discussion of "gap".

Thanks.

I'm going to take a stab at this but in no way guarantee how accurate my answer is. It's been a long time since I've had any geometry classes.

I'll use my truck as an example but these are just tape measure readings and are not exact. My wheelbase is about 141" and the rear axle would be the pivot point. I could look my specs up and get an exact reading but this will be close enough. The distance between my rear axle center and the back of my bed rail is about 46".

If I divide the distance between my rear axle center to the back of the bed rail (46") into the wheelbase (141") that would be 3.065. The wheelbase would 3.065 times as long as the distance from the rear axle center and the end of the bed rail. So if I lower the front axle down 1" I would take the 1" and divide it by 3.065 and it would give a rise of .326" (a smidgeon over 5/16") at the back of the bed rail.

Just take every 1" drop of the front axle (on my truck anyway) and multiply it by .326" and that should give you the answer. If the center of my front axle was 12" lower than the center of the rear axle the end of my bed rail would be 3.912" higher.

To really use this you would have to take into account at how high the trailer axles are in relation to the rear axle of the tow vehicle.

I have not seen a situation where traveling in a straight line if the front wheels hit a 12" dip the rear wheels didn't roll through the same dip. Given that the the tailgate rose about 4" with the front wheels dropping then the tailgate would subsequently drop a corresponding 4" when the rear wheels fell into the dip. Using this "data" a 6" space between the bottom of the 5th wheel frame and the top of the truck rails is more than adequate. HOWEVER, you have failed to mention the relationship/ratio of the distance between the trailer axle/s and the 5th wheel pin. Assuming the trailer wheels will more than likely fall into that same 12" dip that ratio is also critical. The shorter the distance, the more movement will be seen between the bed and the bottom of the trailer frame. Therefore, the relationship of the trailer wheelbase must also be considered when determining minimum bed rail to trailer frame distance.

JMHO but yours may vary.