Why are my BMX brake pads not performing?

Question

This is a ten-year-old Felt "Vault" BMX. I'm old but new to actually building BMX bikes.

I bought it used for fifty USD right out of a garage and immediately noticed the slow stopping of the brakes with older pads, so I just replaced with new ones which of course are a bit smooth.

Then just got back from the bike shop who kindly attempted to tune things after he replaced the tires and tubes.

These are cheap pads and are only on the rear.

1. The cable tree or whatever you might want to call it up near the lever. It's the brake line that turns into to brake lines and just before the tree splits into two there is a breach in the outer cable housing.
   Things got a little stiff maybe it needs a little greasing but never the last my brake-lever action actually pulls the pads to the rim very tight and there is very good performance with the observable action.
   However the end result is not stopping my bike.
2. Now here comes the part where you're probably going to tell me this is the main culprit other than the smooth oily finish of the new pads and yes I will sand those... but lo and behold the only rear Rim I have has this entire anodized coating burned off so now I'm left with smooth aluminum and a little bit of grooving which in my opinion the ladder should be helping.
   That grooving is just like an abrasive material so these pads must be the biggest culprit if not the rim itself.

That brings me to my next question. With a bike looking ugly like this with the front wheel anodized on the rim and the rear wheel all trashy looking is there a product I can coat the walls of my rim with or just repaint the rim with?
What product is that and where is that?

I almost want to just give this bike away. I bought it for $50 USD and between the parts and labor I'm in it another $50 which make me feel stupid for buying the $50 bike when I could have just bought a working $100 bike and not be doing any of this.

Answer 1

If the pads are literally oily, they won't work at all regardless of anything else. Clean them with alcohol, sand a little so you know you're on bare rubber, and thoroughly degrease the rim.

Other than that, it's probably not your brake pads themselves that are causing the problem.

Anodized or painted BMX rims being used with a brake are always going to get down to bare aluminum. They'll also generally brake their best once the coating is worn through. Leave all that alone.

When the detangler and its extra cables and housings are in good condition and properly adjusted, they won't hurt the braking substantively. Getting it there and keeping it there is more hassle than it's worth unless you're using it. It's common to opt to replace it with a straight cable if not.

BMX u-brakes/990-style brakes have their mechanical advantage affected somewhat by the height of the straddle cable. If it were much higher (further away from the rim) than needed, that can cause poor power but with seemingly good, positive feel at the lever. Most of the time, for the cable layout on most frames, it's best to set it so that it's minimally far away from the seat tube in its resting position, or in other words the shortest practical height. (If this was the problem then it might require new lowers for the detangler if you're keeping it).

A final thing to check if the brake is working badly for no clear reason is whether someone put on a v-brake aka long pull brake lever, which will make a u-brake not have much braking power.