I'd like some advice on sidepull caliper brakes. I checked out a co-worker's commuter bike and the brakes just don't work. It feels like the brake pads have no grip on the rims at all. Not being able to stop in time makes the bike unsafe. Now, the brake pads are small little blocks that seems like a very very tough and hard rubber which might be a factor of the problem.
How can I make this bike brake properly?

Thanks in advance!

Side pull brakes, particularly the newer double pivot type, can be very strong and effective if set up and adjusted correctly. As to your co-workers bike:

Are the rims steel or aluminum? Steel rims produce very poor braking power when dry and nearly none when wet. Aluminum rims are far superior.

How old are the brake pads and what quality? Old, hardened pads don't work well, poor quality pads don't work well and mis-aligned pads don't work well. Kool Stop, Shimano and Campagnolo all make excellent pads with Kool Stop being the pad of choice.

Are the cables and housings in good condition and free of broken strands, rust and dirt? Replacements can transform the brakes if the current ones are in bad shape.

Are the brake levers stiff and dirty? Clean and lubricate them if they are.

Finally, are the brakes themselves any good? High quality, rigid brake calipers are fine stoppers. Cheap, flexible calipers aren't.

Yea, I'm going to check all those things. I'll be going to do some maintenance over the entire brake system. (From levers till pads). So ... thanks for the advice on brake pads, now I just need to figure out how to check whether the rims are steel or aluminum? How can you check that? Colour, look, patterns?

Dual pivot brakes have an extra pivot point off center, which helps to increase the leverage, making it easier to brake. See Park Tool's brake repair page for pictures of sidepull vs dual pivot. They have step by step adjustment procedures, too. If you have older sidepulls, here's the repair page for them.
Steel rims are easy to check -- get a magnet.

What kind of bike is it? An old road bike?

One obvious way is with a magnet but if the spokes are plated steel, not stainless steel, a magnet will be less discerning. Try a small magnet on the rim between spokes.

Appearance is also a guide. Most steel rims are either shiny or rusty. Aluminum rims are usually matt finished, particularly the brake tracks.

Thanks for the advice here.
It's an older model of an 'around town' bike. The only thing really is just relubing the cables a bit and putting on new pads.

Maybe one more question you could help me with. The rims are of steel, would Kool Stop, Shimano and Campagnolo still be the right pads to use or is there a particular brand that works a little better on steel rims? Obviously I want to get the most amount of braking power out of the pads.
Thanks again!

I'd go with Kool Stops with the salmon colored compound. It's a relatively soft compound, termed "extreme condition" (aka wet, muddy) by Kool Stop. These pads do stop better in wet conditions, the softer compound is more tacky on the rims than harder "dry conditions" pads, and I think that might be an advantage with steel rims. But just to be clear, I'm not saying the Kool Stops will stop that bike in wet conditions, with steel rims there's no hope of that; I'm just saying the salmon pads might work a little better in dry conditions with those rims.......... Maybe someone with more recent experience with steel rims will have a different idea, though, as I haven't had a bike with steel rims in nearly twenty years ('79 Schwinn Traveler, sold it in the very late '80's). The key factor, though, are the steel rims themselves; they're horrible for braking, and for the wide range of conditions encountered while commuting, are unfortunately going to be dangerous regardless-

No dual pivot will be able to compete with V or disc brakes if that's what you're getting at. Also realize you're usually travelling a lot faster on bikes eqiupped with sidepulls vs the ones on V/discs.

Kool Stop ... thanks! :-)
I'll see what I can get at the shop. (Which I should have done before I opened up this thread haha). No, it's not even a duel pivot, it's a single pivot brake! Oh well. Any suggestions of getting rust spots of the rims as well haha? I can imagine rust spots just eating away of the pads.

Kool Stop salmon compound pads work extremely well on steel rims. The Continental model is your best bet, both for price and likelihood that it will fit the brake calipers.

From my personal experience: Kool Stop salmon pads are grippy, even grabby on steel rims. They are less effective in wet conditions, but they do actually work. Definitely better than any other pad I've used on steel rims.

I wouldn't characterize steel rims as "dangerous." As with anything else, they are dangerous if you ride beyond either the equipment's capabilities or your own. The reduced effectiveness of braking on steel rims requires increased vigilance and awareness of how fast you can safely ride in a given situation, but that's not much of a burden on anyone. Basically, ride smart (which you should be doing on ANY bicycle) and know the limits of the equipment and your skills, and you'll be perfectly safe.

Well, I rode for about a decade on a steel-rimmed bike with rim brakes, so I do have experience with steel rims and braking. That old Schwinn I mentioned was a great bike to ride and was excellent supplemental transportation for me at the time. And I don't remember trying to avoid wet conditions with it necessarily, but the "rush" I got when I hit the brakes in the wet, with very little happening in the way of stopping (at least for a few seconds) is something I'll never forget-

Right on, this really helps me getting on with working on the bike. Good to know all the little facts! I'm sure every improvement to the braking mechanism would be noticeable to this comuter haha, after the brakes being used for so long.

Thanks!

I didn't know that caliper rim brakes were that bad on steel rims in the dry conditions. Mine stopped pretty well on my old 10-speed, even from high speeds. But then again, maybe it's that I got used to the stopping distance and adjusted my riding tactics accordingly?

Now, as for stopping in rain...dang, the first (and only) time I ever took that rig out in the rain, I jumped on the sidewalk ASAP and didn't dare to ride any faster than a pedestrian "jogging" pace. Those brakes just didn't stop, which was particularly harrowing when I almost ran into a car stopped at a red light at the intersection. But hey, it didn't start raining until about 75% of my ride was finished. I still had 3 miles before I could reach my house...