I have an older mountain bike with a chainstay-mounted U-brake. Its really pathetic, the thing barely stops, compared to the front brake. Its almost not worth having. What are my options for turning this into a better brake? Simply new pads and an adjustment to make sure they're working right? I want to keep it, as replacing it isn't really an option. I don't want to have to send the frame out to a builder who could add canti posts on the seatstays if I don't have to. I want to use this bike for loaded touring, and descents make me nervous with that brake.

Sheldon's got some tips that might prove helpful:

https://www.sheldonbrown.com/canti-u.html

I have the same u-brakes on my cannondale,except they are on top of the seatstays instead of the below the chainstays. I finally got mine working good after reading sheldon browns advice about getting the straddle cable short. I used koolstop red eagle claw pads and now it stops as well as the v-brakes on my wifes trek.

one thing to think of is if the frame is flexing when braking.I seem to remember a "u" shaped brace/stiffener to help prevent this. might also consider salmon kool stops.

despite the bad rep these brakes have I am actually quite happy with mine right now

the best thing you can do to improve the u-brake is get a new one. the tektro fx-20 or fx-30 works great. its has linear springs (as opposed to the coil springs on 990s) and uses v-brake pads. its super easy to adjust. i use one on my classic SS converted stumpjumper, and i even take it off roading. excellent stopping power. i was using a dia-comp 990, and the difference between the 2 is night and day.

Hey thanks for the tips! I looked up those Fx-30 u-brakes, and may just try a set. I also saw these. I wish my cable routing was compatible. They look very nice and practical:

https://bmxskateshop.com/Browse_Item_...Evolver_Brakes