I have 3 different types of trailers, GN, 5th wheel and BP, all of them have the Dexter axles. Mine would not lock up either using the process as described in the manual. Years ago, my uncle told me when connecting up my trailers to use them ALWAYS take a minute to GO BACKWARDS and lightly pump the brakes a little while traveling backwards, it will engage the self-adjusters and get the brakes up to speed for use. I tried his method, wallah, my brakes then would lock up per the manuals set up going forward and all of them locked up the same. Beats getting out the jack and manually adjusting each wheel, the self adjusters will set themselves to the correct tension.

CD

 

Apparantly, the self-adjusting feature is only on the heavier 12" x 2.25" brankes and NOT on the 12" x 2". Who knows. I'm going to try the reverse and pump idea and see if I notice any differance. pcm

 

Right you are..the smaller ones needs adjusted with a brake adjusting tool..
Sometimes the self adjusters do not adjust either

 

I have the larger brakes on all my trailers. I also take the time every year to clean and lube the self adjusters when checking the shoes and drums and cleaning all the dust/dirt out. Maybe that's why mine seem to work. Teflon lube goes a long way to keep the self adjuster from becoming corroded and seizing/freezing up.

CD