I'm fixing up an old ten-speed that may serve as an additional commuter. Haven't gotten to the point of adding a rack, etc., yet, but that may be soon.

My other bikes have V-brakes. This bike has sidepull calipers and (I think) steel rims.
I've changed out the brake pads for new, but even so, the stopping power doesn't seem to be nearly as good as on my 2-year-old Trek hybrid or Downtube folder.

Are sidepull calipers just inherently weaker than V-brakes?

I haven't yet changed out cables, and I've never worked on any other calipers, so I don't know if this is just to be expected.

Maybe I'm just riding faster in the drops and thus taking longer to stop!

Sidepulls are weaker, I believe, but definitely the steel rims are hurting your braking performance. Most likely the brake pads aren't the kind made specifically for steel rims and even if they are their stopping power won't be as good as with alloy rims.

Seconding stausty. Your brakes are you secondary issue. You will probably get more benefit from changing to aluminum wheels then you will changing brake types. Plus they'll be lighter, if you're concerned about that, and easier to true if that ever becomes an issue. If changing wheels is not practical then you might consider V-brakes and you should definitely make sure the pads are the best ones to use on steel.

V-brakes would require mounting posts.

There is wide range of quality in sidepull brakes

+1 Modern dual pivot side pull brakes are very bit as good as v-brakes.

Ditch the steel. Bad idea when it gets wet

in my experience I have always felt that the side pull brakes worked better than the v-brakes, but I have never felt like I didn't have enough braking power. I would agree with others that your issue is probably your wheels

Well, considering the bike cost me $5, I can't justify replacing the wheels with new.

On a related note, what is this alloy of which y'all speak? Isn't steel an alloy? Every time I see that word used, I wonder what it refers to.

Would this alloy be non-magnetic? If so, I can easily test the rims.

Steel is an alloy (iron mostly), but in respect to bikes, when people say alloy they are mostly talking aluminum. In general, steel is magnetic, aluminum is not.

On the other hand, since it only cost you $5, you can easily spend a bit on basic aluminum-rimmed wheels with all the money you saved.

The new pads you got have helped, yes, but aluminum rims really will help more.

Also, keep in mind that the other end of the braking system -- the tires -- affects performance as well. Fatter tires with more rubber on the pavement will stop quicker. Even between tires of the same size, older tires or new tires with hard compounds won't brake as hard as grippier tires.

The practical, real-world difference between V-brakes and calipers really comes down to tire clearance, not braking power. That's why you won't see narrow calipers on hybrids and mountain bikes.

Well, the rims are definitely magnetic - as is the frame, of course.

Given this, and the old sidepull calipers with new pads, other than reducing the distance from brake pad to rim, any other tips on improving braking responsiveness and stopping power?

Will replacing cables really make much difference?

Change/buy new calipers. Stamped steel calipers were often used back then, esp on dept store bikes, and flexed a bit too much. Even the most inexpensive single or dual pivot calipers (buy these, easier to center/adjust and better braking) that are available today are light years better and provide more than enough clamping force. If you buy new calipers, the braking performance should be on par with your v-brake equipped bikes. Nutted calipers are still available, but recessed nut calipers are more numerous and you may need to buy 2 fronts and drill a larger hole in the back of your fork to accept the recessed nut. In the rear, the longer bolt will allow you to use a nut for mounting/securing the caliper to the bracket.

As far as steel rims (although they last an outrageous amount of time under normal use), it is better/highly recommended to upgrade to aluminum rims for all season/condition performance and/or reliable/predictable braking when you need it in wet conditions. Plus aluminum rims are hooked rims which allows higher air pressure and superior tire retention. But if you aren't going to use that bike in wet conditions, then IMHO, I wouldn't bother with the extra expense. Salmon brake pads, black/salmon combo pads, or soft black brake pads are good enough. Just remember to "pump your brakes" if you do encounter any wet sections/conditions...wet steel rims are like an old school car with all drum brakes and asbestos brake linings in the rain, need to pump the brakes to dry them off or you won't stop.

New lined cable housing and good quality stainless cables should make a very noticeable difference due to much less friction in the cables and housing.

The British company Fibrax makes brake pads specifically intended for steel rims. Supposed to be MUCH better in wet weather. Hard to find in the USA but Bikesmith Design has posted on the geared hub bikes group that they have them available. Called Raincheaters as I recall.

All that affects is how much travel the levers have before the brakes engage. If you can lock up the brakes before the lever hits the handlebar, you're not lacking braking power, even if the caliper is opened up a little bit.

(personally, I set up my brakes a little "loose", because I feel like I get better modulation and not such a sudden on-off response like I get if they're really close to the rim... that's mostly a personal preference, though)

Replacing cables won't make any difference unless they're about to snap or if they have a LOT of drag. The biggest problem of dirty, dragging cables, though, isn't in activating the brakes, but releasing them. Your hands are stronger than the return spring on any brake, and if anything gets affected first, it's the brake spring opening back up and pulling the cable taut after you've released the lever. If that's not an issue, then the cables don't need replacing.

Again, the next logical step for the biggest improvement on your bike is new rims. $100 wheels on a $5 bike is still a whole bike for around a hundred bucks, and it's probably still better than any $100 department store bike.

I have used " Kool Stop Salmon " brake pads to increase stopping power on steel rims, & am satisfied. ALSO, wipe down the side of the rims often, with alcohol, carb cleaner sparyed on a cloth, . Still , will not be great when wet, but will be a lot better.

...brazing V-brake studs to the frame.

tcs

The real problem with steel rims is in the wet. Either get the wheels replaced or don't ride this bike in the rain.

At the moment, I don't intend to ride this bike in the rain. (No fenders, for one thing!)
It may just remain my "fun bike", but it'll be a lot more fun if I can be confident about being able to stop when I need to!