I've got a 1990s Trek 1400 with 105 brakes. When I apply the brakes they feel soft. I replaced the cables being careful about routing, etc. with no improvement. The calipers themselves visibly flex when the brakes are applied hard. Nowhere near the solid feel I get with the v-brakes or cantis I'm familiar with. Is this normal for caliper brakes? This is my first bike with caliper brakes since the Schwinn Varsity I grew up with in the 70s.

It's impossible for us to see firsthand or feel your brake flex but yes, they won't have as solid a feel as the other styles you mentioned, other things being equal. The only thing you can do to reduce overall flex in the system is to make sure you do not have extra, unneeded housing length. But stopping power is not necessarily the same as stopping ability. If you have enough strength then you can stop equally quick no matter what type of brake you have. Once the wheels lock or the bike starts to pitch over stopping power is irrelevent. As posted in another discussion https://www.bikeforums.net/showthread...s-Rear-Sliding , what will stop you fastest is technique.

distance between brake pad, and where the brake is bolted to the frame is longer.
+ maybe the slop around the pivot bolt is loose, and the brake is out of adjustment

IDK, this is just a text device.

Are they single pivot or dual pivot brakes?

If they're single pivot, that's the problem.

The dual pivot calipers on my bikes are stronger and have a more solid feeling than the cantilevers on my other bikes.

I have a set of single pivots on a bike and they do feel far squishier than v-brakes but don't worry, they will stop the bike just fine. I wondered about the squishyness too but v-brakes to caliper feel is apples and oranges.

Even the double pivot brakes I have on another bike feel squishier than v-brakes.

Thanks for the info. This is an older bike and I love the way it fits and rides, but a few of the components are lacking despite being older 105. The brake caliper arms themselves visibly flex when the brakes are applied hard. Braking is a big issue on this bike partially because of brakes, partially because of rims. Rims are getting replaced with newer wheelset with machined braking surfaces. If that doesn't provide adequate stopping power I'll look at replacing at least the front brake with a dual pivot. As the bike is set up now, the braking is poor to fair when dry and downright scary when wet. Old hard anodized rims don't help.