Rim vs mechanical disc: knowing what you've got
Okay. New module. We did flats, we're done with tubes and tires for now, and we're moving into brakes. First thing, before we touch a single cable or pad, is figuring out what kind of brake is actually on your bike. You'd be surprised how many people don't know. That's not a knock on anyone, it's just not something you think about until something's rubbing or not stopping.
There are basically three flavors you'll run into with a home bike. Rim brakes, mechanical disc, and hydraulic disc. We're covering the first two in this module. Hydraulic's the one I'll be straight with you about right now, up front: I don't bleed hydraulic systems for a living, I don't do it often enough to teach it well, and if that's what you've got and it's not working right, that's a shop trip. Not because it's impossible, just because messing up a hydraulic bleed at home can leave you with brakes that don't work at all, and that's not a place to learn by trial and error. Everything else in this class, trial and error is fine. Not that.
How to tell what you've got
Look down at your wheel, right where the tire meets the rim.
Rim brakes are the classic ones. Two arms, one on each side of the wheel, with a rubber pad that squeezes directly against the rim itself when you pull the lever. If you see pads pressing on the metal part of the wheel, that's a rim brake. Most cheaper bikes, most older bikes, a lot of commuter and kids' bikes still run these. Simple, cheap to fix, easy to see what's going on because it's all right there in the open.
Disc brakes move the whole operation down to the hub. There's a metal rotor, looks like a little disc, bolted to the center of the wheel, and a caliper that squeezes pads against that rotor instead of the rim. If your wheel looks clean at the rim and you see a flat metal disc near the axle instead, you've got disc brakes.
Now, within disc brakes, mechanical versus hydraulic. Mechanical disc uses a cable, same kind of cable as a rim brake, just routed down to the caliper at the hub. Pull the lever, cable pulls the arm, arm squeezes the pads. You can see the cable housing running all the way down to the brake. Hydraulic disc has no cable at the caliper end, it's a sealed line, usually a bit fatter and smoother looking, running fluid instead of pulling a wire. No visible cable attachment at the brake itself is the giveaway.
That'll get you most of the way there just standing in your garage looking at your own bike for two minutes.
Why it matters which one you've got
Here's the thing. The adjustment mechanics are different enough that "brake advice" isn't one-size-fits-all. Rim brakes, you're dealing with pad position relative to the rim, and the rim itself has to be reasonably true or the pads will rub unevenly. Mechanical disc, you're dealing with caliper position relative to the rotor, and the cable tension. The lever end is basically the same on both, it's what happens at the other end of the cable that's different.
I mention this because I had a moment last year that I still think about. I was trying to walk Jennifer through fixing her own flat before a group ride, and about halfway through explaining it I drifted off mentally, started thinking about whether we needed to push the ride start time back. She just finished fixing it herself while I was somewhere else in my head. Fixed it fine, by the way. I apologized after. But the lesson I took from that isn't really about flats, it's about this: people can usually do more than you think if you just tell them clearly what they're looking at and let them go. So that's what I want you doing right now. Look at your own bike. Don't ask me first. Tell yourself what you've got.
What most people actually need
My honest opinion, and I'll say this every time it's relevant because I believe it: most people's brakes aren't broken. They're dirty or they're out of alignment. Almost nobody actually needs new pads or a new caliper when the real problem is grime on the rim, or a cable that's stretched a little and needs a barrel adjuster turn, or a rotor that's got some road grit baked onto it. We'll get into the actual adjustments in the next couple lessons, one for rim, one for mechanical disc, because the steps really do split at that point. But the diagnosis step, the "what do I have and is it actually broken or just dirty," that's the same mindset either way. Clean and look before you buy anything.
If you've got hydraulic and it's making you nervous, that's fair, and that one really is a shop call for anything beyond wiping the rotor down with isopropyl alcohol, which is safe and worth doing regardless.
Before next time
Go find out what's on your own bike, rim, mechanical disc, or hydraulic, and bring that answer with you. We're splitting the room next lesson based on what everyone's actually working with.