Can I use V brake levers for U brakes (side pull calipers)?

I found this helpful site which explains the different types and compatibilities:

Mechanical bicycle brake compatibility

2. Types of brake levers and calipers

These are the brake lever types with their amount of cable pull per full lever travel (about 20 degree angle):

• V-brake (also known as Direct-pull, or linear-pull), 15 mm
• Cantilever (also known as center-pull and direct pull), 7 mm
• Old road, 7 mm
• New (SLR and Super SLR) road, 8 mm

Here’s a list of mechanical caliper types with their ideal amount of lever cable pull:

• V-brake (also known as linear pull brakes), 15 mm
• Mini V-brake, 7 mm
• Cantilever (also known as center pull brakes), 7 mm
• Old road calipers, 7 mm
• New road calipers (SLR and Super SLR), 8 mm
• MTB mechanical disc, 15 mm
• Road mechanical disc, 8 mm
• U-brake, 7 mm
• Roller brake, 7 mm

Conclusion

Regular V-Brake levers are not comaptible with U brake calipers

Really useful info about pull ratios and the answer is most certainly strictly correct, although from a practical perspective, I'll share my thoughts. A v brake lever will pull 15mm of cable whereas a road lever will pull through only 7 on 20' of deflection. So whilst you couldn't use a road lever on a v brake (you couldn't pull sufficient cable to engage the v brake far enough) , you could use a v brake lever on a normal road side pull to move the brake sufficiently to engage it on the rim . The difference would be that the travel on the lever would be less (about half) to engage the brake calliper on the wheel rim but you would still be pulling the side pull brake through its ideal range. It can't travel "too far" as the wheel rim is engaged to stop any excess travel (and you'll stop).

I've put v brake levers on an old 1970,s Dutch bike with side pull shimano brakes for my wife who didn't like dropped bars. Works fine - well in fact. I had thought that it would make the brakes twitchy or coversely reduce the stopping power as you might be losing some mechanical advantage, but in the set up I did (which was using super cheap levers off e bay) the brakes work well and the bite point on the brakes feels quite natural and solidly reassuring. The extra travel available seems to take up any flex (70,s calipers and £5 levers so they're probably both rubbish) in the system, meaning that the braking is actually very positive.

So, in summary, v brakes and side pull brake set ups are definitely different in terms of pull ratio, but in my experience, v brake levers with side pull callipers worked with some success.

If you were wanting to use road levers with v brakes, (based on the ratios quoted above) you'd have to swap out the v brake calliper for cantilevers, and put those on the v brake frame / fork posts to get sufficient calliper travel. Some "adventure / touring / gravel / cyclocross bikes seem run this set up as stock anyway.

Other people's experiences may be different to mine so take care with your own set up and thoroughly test the braking you end up with to your own satisfaction before using in circumstances where you might rely on the brakes for your own safety; I'm only sharing how it worked out for me.