Cleaning the pads and rim before you buy anything
Okay. We know what we've got now, rim brakes or mechanical disc. Before we touch a single adjustment, before anybody spends a dime on new pads, we're cleaning what's already on the bike. This is low key the most skipped step in the whole brake conversation, and it's the one that fixes the most problems.
Here's the thing. Most people's brakes aren't broken. They're just dirty or a little out of line. Squealing, grabbing, feeling weak going down a hill... nine times out of ten that's grime and glaze, not worn-out parts. Buying new pads before you've cleaned the old ones is usually skipping the actual fix. So we're doing this first, always.
What you're looking at
If you've got rim brakes, your pads are two little rubber blocks that squeeze the sides of the rim itself. If you've got mechanical disc, your pads are small metal-backed pieces squeezing a rotor near the hub. Either way, same idea: two surfaces need to meet clean and even. Dirt, oil, and brake dust in between is what's making things grabby or squeaky or weak.
Cleaning rim brake pads and the rim
Pull the wheel, or at least get it out of the way enough to see both pads clearly.
Look at the pad surface first. If it's shiny or has a hard glaze on it, that's brake dust baked on from heat and friction. That glaze is slick, and slick pads don't grip. Take a bit of sandpaper, something in the 100 to 150 grit range, and scuff the pad surface until it's dull and a little rough again. Don't overthink the grit number, you're not doing woodworking. You just want texture back.
While you're in there, check the pad for embedded bits of grit or metal shavings. Sometimes a little rock works its way into the rubber and it'll score your rim every time you brake. Pick it out with a pick or the tip of a flathead if you've got one. Small thing, but it matters.
Now the rim. Wipe the braking surface, the sidewall the pad actually touches, with a rag and some isopropyl alcohol if you have it. Water works in a pinch. You're getting off road grime, old rubber residue, and any oily film. If you've ever gotten chain lube on your hands and then touched the rim without thinking, that film is exactly what we're chasing off. Oil and rubber pads do not get along.
Don't use household glass cleaner or anything with ammonia on the rim if you can help it. It's not a huge deal once, but it can dry out the rubber over time and you don't need the chemical exposure on your hands either. Alcohol or plain soap and water. That's it.
Cleaning mechanical disc pads and the rotor
Disc setup is less forgiving about contamination, honestly. Any oil on that rotor and your braking goes soft and unpredictable, sometimes for weeks until it wears off.
Pull the pads out of the caliper, usually a small pin or clip holds them in, check your specific caliper before you go yanking on it. Same deal as rim pads: if the surface is glazed, scuff it lightly with sandpaper.
For the rotor, alcohol wipe only. Do not touch the rotor surface with your bare fingers if you can help it, the oil from your skin is enough to cause noise and reduced stopping power. I know that sounds fussy but it's true, I've watched a squeaky rotor go dead silent from nothing but a good alcohol wipe and me remembering to hold it by the edge afterward.
While you're at it, check for wobble
This is a good moment to spin the wheel and watch the rim or rotor go past the pad. If it's wobbling side to side more than a little, that's a separate problem, and it's honestly not as scary to fix as people think.
I trued my first wheel with zero tools made for the job. No truing stand, just a couple zip-ties cinched onto the fork as a fixed reference point, so I could see exactly where the rim was drifting toward one side as it spun. Took me close to an hour, wasn't perfect when I was done, but the wobble was gone and the rim stopped clipping the pad. Good enough to ride on. I still true wheels that way about half the time. Eventually I did buy a stand, drove clear up past the point of the mountain to grab a cheap one off a marketplace listing, and it turned out to be slightly warped itself. Used it for a year anyway. You don't need the fancy version to start. You need a reference point and some patience.
Before next time
Pull your pads, give them a look and a scuff if they're glazed, and wipe down the rim or rotor with alcohol. Don't touch anything else yet. We'll get into actual adjustment next, and it goes a lot smoother on clean surfaces.