This Instructable will explain how I made some slicks for one of my bikes. You can do the same, just remember to wear appropriate safety gear, (A glove and a breathing mask as a minimum, a plastic raincoat would also be recommended.)
Step 1: Tools and Equipment.
To do this you will need some type of directional sanding tool, by which I mean either a belt sander or an angle grinder with a sanding pad like I used. You will also need a straight and true front wheel that matches the tires you want to sand and a bike flipped upside down so you can use the forks as the wheel mount. Probably best to use a bike you don't care as much about as it will get messy as shown in the photo, the rubber does however easily hose off.
With the tire you want to sand mounted on the wheel and inflated to around 5psi below it's recommended maximum, (The air will expand and increase pressure as some heat is transferred to the air inside while sanding.) and also mounted on the bike fork, check it spins easily and true, if it doesn't you will end up with flat spots on your tire which will more than likely lead to sanding too much off and exposing the canvas in places.
Hold your sander in your dominant hand and with your other hand in a glove hold the wheel from spinning, start sanding each knob down to where it is almost even with the rest of the tire, working your way around the tire on one side. Once you have them all evenly close to the smooth portion, release a bit of pressure with your glove hand and allow the wheel to spin as you are sanding, you will find you can adjust the speed of the spin by varying the angle of the sanding disc and what portion of the disc touches the tire, with a bit of practice you will end up with something like the tires pictured here.
Step 3: Repeat for the Other Side.
Just as the title says, repeat for the other side and you will end up with a nice even slick for your bike just like the ones in these pictures.
The next step will give some pointers on which tires are best for making slicks and why.
Step 4: Which Tire Is Best?
I did a bit of experimenting with different tires to find what tires are the best for doing this, I even tried three identical tires but that were of different age and condition.
The three matching tires I had were all the same brand but 1 was brand new, never used and never been in the sun, 1 was slightly used but left in the sun for a year, and the last one was practically new but left in the sun for approximately four years.
The results were interesting considering these were all the same brand and model tire, the older and harder the tire was, the better the end result! The brand new one flexed it's rubber knobs so much as it was being sanded that it sanded through in places as you can see in the main photo for this step, the slightly older one was nice and even but ended up weighing less than the oldest one, indicating that more rubber was taken off it to achieve the smoothness required.
After doing those I went looking for the oldest and heaviest tire I had, which was the Kenda Comp pattern tire in the other 2 photos on this page, it was approximately 10 years old and had been left in the sun for most of it's life, the bike it came off was found at the back of a scrap metal yard where it had been for many years, It had no cracking on it but was really hard, the results of this tire were the best of all, really smooth and the most rubber thickness left when finished.
So the best tire to do this with is one that is harder, and possibly older...
Step 5: Clean Up!
Cleaning up the bike/fork/rim and tires is easy, just get out your garden hose and give them a good rinse, clothing is another matter, you can hose them off as best you can but put them in the wash by themselves or with a rag load, not with your best evening wear, I would even recommend doing an extra "no clothes" load after to ensure all the rubber dust is gone. Best bet would be to wear a throw away plastic raincoat and save yourself the hassle...
If you like this Instructable why not check out my other one here: https://www.instructables.com/id/Making-wide-bike-wheel-hubs-and-joining-them-to-ca/
The last 3 photos are from that Instructable...
Have fun and be safe!