Interesting range of responses.
I have a 14,000 5er and have it on 10. Never locked up the trailer brakes and it doesn't feel like the trailer is over braking. My controller has stayed on 10 for nearly every trailer I've pulled in the 6 years I've had this truck. 2 of the trailers I towed were for our sportscar race team. We had an enclosed 48ft gooseneck that carried 2 Mustangs and all our tools, spares, tires and fuel. It went about 20,000 lbs. We also had a 44ft toy hauler that had a Miata in the back. With the Miata, it went about 15,000. Always just left it on 10 and it seemed to do fine. My teammate had an identical truck and did the same.
My old 5er camper was about 8500 lbs, but the brakes on it never felt like they worked well. I replaced all the brake assemblies, checked the grounds and voltage through the system and it just never stopped well, so I just left the controller on 10.
The only time I lowered the setting was when I was pulling our 24 ft single car trailer running empty. I could lock up the tires on it pretty easy on 10.
For those running less than 9 or 10 with big trailers (over 10,000), how did you decide on a lower number? Did you feel that much difference as you went lower?
2016 Coachmen Chaparral 390QSMB
2011 F350- CC, DRW, LB, PSD
2016 nights camped: 40