Gain sets how hard the trailer brakes apply relative to the tow vehicle. The right starting point comes from the weight ratio between trailer and tow vehicle, then you confirm it with one road test.
Fill in the fields above and the answer appears here.
A lighter trailer needs less braking force to slow the same amount, so a gain tuned when loaded will lock the wheels when empty.
Use an empty lot or a quiet straight road, get to about 25 mph, and pull the manual override lever on its own without touching the vehicle brake. You are feeling for how hard the trailer alone pulls you down.
Yes. Reduced grip means a gain that was fine when dry can lock the trailer wheels. Back it off a step or two in the wet.
Method last reviewed 2026-07-29. Figures are guidance, not a substitute for the ratings printed on your own equipment.