My 10 year old son has a Redline Raid he got about 2 years ago. Probably one more year on it before we have to upgrade him to a larger bike. It has a coaster brake and a rear V brake. I'm thinking about adding a front caliper brake since there is a hole in the fork crown where a caliper brake could mount--unless it's simply a fender mount hole.

Tires are very knobby (57x406 front, 47x406 rear) and starting to show a bit of wear, so I was thinking about swapping on a set of road tires when I add the caliper brake. He's not an offroad bike riding kid, even though he sometimes imagines he is.

I wanted the front hand brake to get his brain thinking about hand brakes, since his next bike will likely be a multispeed with hand brakes. Also, his 22 month old brother will eventually inherit the bike, so I don't think it's a bad investment.

Any info or links about performing such a surgery would be greatly appreciated.

Sheldon's article on caliper brakes will help you: https://www.sheldonbrown.com/calipers.html

You need to measure your reach in order to buy the correct brake. You also need to determine whether your fork is drilled for a recessed nut (probably not.) If not, you need to buy a brake with an external nut or drill out the back of the fork to accommodate the recessed nut. All of this is covered well in the article.

You should definately add a front brake to the bike. Although there are already two brakes (meaning you can still stop the bike if one fails) the front brake can stop the bike more effectively than the rear brake and it's a good idea for your son to get in the habit of using it rather than relying on the less effective rear brake. The coaster brake or rear handbrake are ok for general slowing down, but knowing how to properly use the front brake may one day save his life out on the road.

Caliper brakes require different levers to v-brakes. Make sure you get the correct lever (and don't let anyone tell you there's no difference) as using the wrong lever type will result in a brake that feels nice and firm, but can't be pulled hard enough to be any use.

As others have said, adding a front brake is a good idea.

You said "Probably one more year on it before we have to upgrade him to a larger bike." Don't make the mistake that many parents make of thinking that a kid should be put on a larger bike as soon as possible so that he can "grow into it." You could probably keep him on that bike longer than you think. Most kids are perfectly happy to stick with a 20" bike until they start driving.

But if you do decide to get a new, bigger bike for him sometime in the future, at least wait until he's really outgrown his present bike. Buying a dangerously oversized bike is false economy. You'll end up buying exactly the same number of bikes either way, so what's the point of putting him on a bike that he might not be able to handle safely?

Many thanks for all the great responses. I measured the reach and it's 78mm. Not drilled out for a recessed nut. 6mm hole.