Let’s start with some of the most popular bobber and chopper front tires, the “Avon Speedmaster”. This is probably the most used tire when building. It has a great look to it and it’s a relatively inexpensive tire. The “Avon Speedmaster” front tire can be purchased in a number of sizes that range from 18 inches to the often used 21 inch.
Dunlop Makes a few nice bobber and chopper tires. The Dunlop K81/TT100 4.25 x 18 rear tire makes a great choice for your classic bobber build. Keep in mind if you’re building a bobber out of a Triumph or BSA you won’t be able to fit much more than a 4.50 inch tire without doing some extra work to your wheel, drive sprocket and your hub sprocket.
The most important parts of a build are the gas tanks and tires. Nothing else will change the look as much as these two factors. Choosing the right stance for your build is very important. You can use a 21 inch front wheel and tire to take up space between the frame and the tire. You can use a 16 inch wheel out back and give the bike a mean low look. And there’s always the 18 rear for that classic clean look. Keep in mind that as you drop down from an 18 inch to a 16 inch rim, tire choices change dramatically. A 16 inch wheel will have a much lower and wider tread print.
If you’re going to be riding your bike a good deal, get the tires balanced. A good balanced tire makes a huge difference on both the ride of the bike and the way your tires ware. If you’re all about looks and just shooting down the street and around town, who cares.
If you’re going to use the 16 inch rim and you’re looking to get a wide tire on the back of your Triumph or BSA bobber or chopper, you can shim the sprockets for clearance. The entire brake hub can be shimmed to give you more room. The rear sprocket can be shimmed to give you more room and the drive sprocket on the motor can be shimmed to give you more tire room. In order to get a good fat tire in the back you’ll need to do all three. Each providing you with a little more room. 3/16 of an inch on both sides is actually a pretty big tire. You can find articles and videos on the internet to help you understand how this all works.