Tongue weight too light

If your tongue weight came in under the recommended range — below about10% of trailer weight for a conventional bumper-pull — that's the dangerous direction. Too-light tongue weight is the leading cause of trailer sway.

Symptoms of too-light tongue weight

• The trailer sways or fishtails at highway speed, in crosswinds, or when trucks pass.
• The rear of the tow vehicle feels light; steering feels vague.
• On a scale, tongue weight is under 10% of the loaded trailer weight (under ~5% for a boat).

Why it happens

Tongue weight is set by where the load sits relative to the axle. When too much weight is behind the axle — or the trailer's own balance point is too far back — not enough presses down on the coupler. The trailer then pivots around its axle and oscillates. You can see this directly in theload-placement calculator: drag the cargo rearward and watch tongue weight fall.

How to add tongue weight

1. Move cargo forward, toward the coupler. Aim for ~60% of the load ahead of the axle.
2. Put heavy items at the front — battery, propane, tools, water — near the A-frame.
3. Re-measure after each change (small shifts move tongue weight a lot), until you're back in the 10–15% range.
4. If the trailer is balanced correctly but still light, a trailer with an adjustable axle can be moved rearward — but confirm with the manufacturer first.

Don't tow until it's fixed. Check the corrected number in the calculator.