Why do I need WD?

jmtandem wrote:
Snip... If the trailer is towed level there is no nose dive even if the trailer brakes do not lead the tow vehicle's brakes. Snip...

I am not an engineer but that has NOT been my experience at all. I think the reason is that the center of mass is higher than the axles and that causes the trailer ( or car for that matter) to nose dive on braking. Every vehicle I have been in or owned did a nose dive, at least a little bit, when the brakes are applied.
If that nose dive occurs when going down a hill, on a curve, towing a trailer, then the results can be less than desired! :E

jmtandem wrote:
Think through your answer thoroughly. If the tow vehicle and the trailer are properly set up and the driver wants to stop, the TT brakes stop the TT, the TV brakes stop the TV and if the TT brakes slightly lead the TV brakes the nose dive stuff you talk about will not happen as the trailer is stopping stronger and faster than the TV. It is simple to understand since the TT is actually stopping first and faster it is not nose diving the rear of the TV and raising the front TV axle. Snip...

It has been my experience that the nose dive will still happen because the "lead" of the trailer brakes only happens for a short time, and also the trailer brakes are usually not as strong as the truck brakes. It has not been my experience that the trailer will stop stronger and faster than the TV. This may not be the case if the trailer has disk brakes but I have never had a trailer with them.
Barney