Ron Gratz wrote:
IMO, if the added drop due to behind-the-axle weight is unacceptable, it is better to compensate for that added drop by using a rear suspension aid.
The problem with using the WDH to compensate for rear end drop due to bed load is that doing so will contribute to undesirable oversteer.
When load is added behind the TV's rear axle, load on the rear axle will increase and load on the front axle will decrease. This, by itself, will increase the tendency to understeer.
However, the behind-the-axle weight also causes the TV's center of gravity to move rearward. That makes the front tires more effective at steering and the rear tires are less effective. This, by itself, will increase the tendency to oversteer.
The two effects -- 1) changing the axle load distribution and 2) moving the CG -- tend to cancel each other.
If you then use the WDH to compensate for the effects of bed load, you are decreasing the rear axle load and are increasing the front axle load. This increases the tendency toward oversteer -- which is not a good thing when towing.
In the past few years, TV and WDH manufacturers have been specifying reductions in WDH load transfer based on directional stability considerations.
IMO, using more highly rated WD bars to achieve more load transfer is in direct conflict with the recent changes in Front Axle Load Restoration specifications.
It took some time for the WDH industry to make the FALR changes and, I guess, it'll take some more time for them to change their minds about using the WDH to compensate for bed load.
Ron,
But doesn't the TW of the trailer also decrease the front axle weight while moving the TV center of gravity to the rear? By your logic, the under/over steer should cancel each other out and we wouldn't need a WDH is the first place.
It doesn't seem to make sense that 600# placed in the bed behind the rear axle has a different effect than 600# placed under the bed behind the rear axle.
I'm inclined to agree with Reese, Progress and eTrailer that behind the axle weight in the bed needs to be taken into account when selecting the right bars as
some of that weight will be redistributed.
From a FALR perspective, it seems to me that 100% FALR number would be the load measured with my truck full of passengers, fuel and cargo in the bed in front of the rear axle but nothing in the behind the rear axle in the bed (or in the trunk! as I have a Honda Ridgeline ;)
Granted, in my particular case...I don't have enough payload left to really carry much in the bed or trunk given my trailer TW. So it doesn't matter to me. But for those with more payload...
