Tongue weight plays a role in three different major areas:TTW can range from 10-15% depending on the trailer and it's design. Open trailer are lower, enclosed and travel trailers a bit higher, though again depending how it was designed. If you are having an issue towing a trailer, weighing it is the best way to find out if you have an issue or not. BUT, you may need to in crease tw to make that trailer a little more stable even if the tw # looks good. I have a travel trailer (tt) that at 12.6% tw it wasn't 100% stable. While I haven't reweighed it yet, I moved some things around to increase the tw and it is stable now.
- How well the trailer "stays put" while you're pulling it. If the level is too low, the tongue / draw bar will sort of just slop around on the hitch and the trailer will feel very squirrely behind you. This will make the whole entire setup feel unstable because the draw bar will be trying to sway the rear end of the tow vehicle.
- Squat in the rear of the tow vehicle (or lack thereof). Too much weight puts too much squat in the rear, too much weight on the rear axle and suspension. Too little, and you'll lose traction for acceleration and anti-sway in the rear end because the trailer will actually be LIFTING the rear end off the ground.
- Weight borne by the front axle. Too much tongue weight removes weight from the front axle and will significantly decrease steering input / responsiveness and braking ability.
When you need to up the tongue weight to add stability to the trailer, you increase the amount of weight that you need the tow vehicle to carry. If the actual weight is within the limits of the tow vehicle's capacity to carry directly, you're good. But, if it goes over, you need to use a Weight Distributing Hitch so that a portion of that total weight is actually transmitted to the FRONT axle for carrying instead of trying to carry it all at the rear axle. The WDH changes the leverage that the trailer applies to the tow vehicle so that some of that weight ends up on the front suspension, and this keeps braking and steering input appropriate.
Much like the weight distribution ON the trailer needs to be correct to get the right tongue weight, the setup of the WDH needs to be correct in order to split the carrying load correctly between front and rear axles. There's quite a bit of science to get it all exactly right, but practice and such go a long way for you to know immediately when something doesn't feel right.