How Choppers Work

Choppers tend to be based off of traditional motorcycles or cruisers, which have a different style from other bikes. Unlike sport bikes, where the rider leans forward, choppers are usually designed so that the rider sits low in the seat, leaning back, arms outstretched. This provides a relaxed riding experience.

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To get this look, a chopper has to have the right frame. There are two main kinds of frames used in choppers: hard-tail frames and soft-tail frames. A hard-tail frame is a solid frame with no rear wheel suspension system. Hard-tails have the classic lines that chopper enthusiasts love, but they tend to give very bumpy rides.

Soft-tail frames have rear-wheel suspension, meaning the frame comes in two major pieces. The front part of the frame is where you'd mount the engine, transmission, fork and handlebars. The rear section is where you'd mount the rear wheel. You connect the two sections together using bolts, brackets, spacers and other equipment, depending on the frame's manufacturer.

At the front end of the frame, whether it's a soft-tail or hard-tail, is where you mount the fork assembly. The fork assembly is the part of the bike that connects the front tire and handlebars to the frame. The fork assembly also includes the front wheel suspension system, which usually either uses springs or hydraulics.

In the next section, we'll learn about a chopper's rake and trail.

Whether you're using a hard-tail or soft-tail, one of the most pivotal decisions you'll make regarding your bike has to do with the bike's rake and trail. You may have seen some choppers that look really stretched out, with the front wheel sitting far out in front of the bike's frame. Bikers can get this kind of look by adjusting the rake of the bike. The rake is the angle formed between the neck on the frame of a bike and a vertical line. The bigger the angle, the further out the front wheel will be from the frame.

The distance between the point where the tire makes contact with the ground and a vertical line from the center of the front wheel's steering axis to the ground is the bike's trail. Trail is measured in inches, and in motorcycles should always be a positive number -- a negative trail means an unstable ride. Trail is important -- too little or too much trail and the bike will be sluggish or even impossible to control. Bike experts all have different opinions on what's the ideal trail length, but it tends to range between 3.5 and 6 inches.

While there's a relationship between a bike's rake and its trail, it's not always obvious. In most cases, increasing the rake of a bike's frame will increase positive trail, though this depends on what kind of fork assembly you use. In order to increase the rake of a bike without making the trail too large, some bikers use raked trees. Trees mount the fork assembly to the neck of the frame and usually have two sets of mounting brackets of equal length. A raked tree's brackets are at two different lengths, allowing the builder to set his fork assembly at a different angle than that of the frame's neck to the vertical.

Once you've got your frame and rake set, it's time to start looking at what you're going to mount on this monster. The world of choppers is full of options, so no two bikes are going to be the same. Chopper builders need to consider how the various parts are going to fit together, whether they'll need to offset components and how it will affect the bike's performance and balance.

In the next section, we'll examine how the guts of a chopper fit together.

Bike builders have a lot of choices when it comes to engines and how to mount them. Engines come with names like Evo, Twin Cam, Shovelhead, Panhead and Knucklehead. Some engines work better with certain frames -- in fact, some frames are designed specifically to hold a particular engine. Builders have to be aware of an engine's dimensions to make sure they have the right amount of clearance in their frame once they've installed all their components.

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Some builders prefer to mount their engines directly to the frame of the bike as part of the "less is more" philosophy the chopper seems to embody. Engines like Harley-Davidson's Twin Cam 88B come with counter-balancers, which help reduce vibration, making it ideal for those who want to mount the engine directly to the frame. Engines without a counter-balancer system can give off a lot of vibration, so if you mount the engine directly to the frame, all that vibration will affect your ride, making it much less comfortable.

Many builders choose engines based on the look they are going for. Someone building a chopper designed as a throwback to the classic choppers of the '60s will want an engine that looks like an old one. He or she can either purchase an old engine and do some work on it, rebuilding it if necessary, or buy a new engine designed to look like the classic engines of the past. New Shovelhead engines look much the same as they did back in the '60s, but today offer bikers choices in everything from the compression ratio and camshaft to an electronic ignition.

Unlike most car engines, a bike engine's appearance is everything. That's because most choppers don't cover up the engine -- it's on full display. Harley-Davidson offers engines in black and chrome, for example, which usually increases the cost of the engine by about $1,000 over the less flashy aluminum versions.

In a similar vein, chopper transmissions need to be flashy as well. Many companies sell transmissions designed to match specific engines. Transmissions sit behind the engine and come in four-, five- and six-speed varieties. Most modern choppers use either five- or six-speed transmissions -- only older choppers or bikes designed to look like vintage models use a four-speed transmission.

Most companies design frames to hold a particular kind of transmission, though many companies sell special cases that give you more choices. For example, you might need a special transmission case to mount a five-speed transmission on a frame that normally would carry a four-speed transmission. The case mounts to the frame, and you mount the transmission to the case. Otherwise, the transmission and frame wouldn't match up, and you'd be stuck with a bike and a transmission that don't fit together.

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The transmission powers the drive system for the chopper, which is either a chain system or a belt system. Chains and belts connect one side of the drive system, the transmission, to the other side, the rear tire. Transmissions only provide power to the rear tire; the front wheels aren't powered. A small sprocket in the drive system turns the chain or belt at the transmission end, which then turns a larger sprocket at the tire end, making the tire move. Most choppers use an open primary system, meaning the belt or chain isn't covered by housing or casing -- it's left out in the open for all to admire. It also means that you need to pay attention when riding one because you don't want to get caught in the chopper's drive system.

A recent trend in chopper design is to use wide tires in the rear. In order to provide power to a wheel with a wide tire, builders have to offset the transmission to one side, particularly if it's a belt system. Without offsetting the transmission, the belt would not have enough clearance from the rear tire. By offsetting the transmission, a builder can make sure there's plenty of clearance. Unfortunately, offsetting the transmission too much can hurt a bike's stability and, perhaps worse in the eyes of a chopper designer, make it look less impressive.

In the next section, we'll look at the other components of a chopper and how they set these bikes apart from other motorcycles.

Bikers can customize practically every part of their chopper. There's a huge aftermarket that supplies bikers with dozens of choices for wires, cables, brake lines, calipers, wheels, tires, seats, gas tanks, exhaust pipes, fenders and headlights, among other components. Depending on how much you want to spend and how detail-oriented you are, you can handpick custom bolts and capscrews to give your bike a unique and personalized touch.

Customized gas tanks are particularly popular with chopper builders. Older bikes had gas tanks that builders mounted directly to the frame, sitting on top of the bike. Many modern choppers have tanks that are molded to fit with the lines of the frame, giving the bike a more unified, clean look. Fabricators make gas tanks from sheet metal, molding or beating it into the right shape. Motorcycle gas tanks usually only carry a few gallons of gas -- it's rare to find a tank that can hold more than seven gallons.

Bikers can also use sheet metal to make customized fenders for the wheels, though many choose to leave fenders off the front wheels entirely. Fenders need to allow for plenty of clearance from the tire, particularly if the bike has a rear suspension. The tire should clear the rear fender even if the bike bottoms out, meaning the suspension is compressed to its maximum amount.

A good bike seat can help make a ride comfortable and stylish. A popular style on old choppers is the king and queen seat, which is designed for two riders. The seat for the first rider is set lower and in front of the seat for the second rider. Other bike seats include solo rider designs, gunfighter seats, tour seats, rumble seats and stinger seats. If you can't find a design that fits with your vision of the perfect bike, chances are there's someone out there who can make a customized seat just for you.

A quick Internet search will turn up dozens of shops where you can buy the perfect finishing touches for your bike. You can choose to make your bike as fancy as you like, or go with a bare-bones ride that does more with less. It's always a good idea to check your local motorcycle laws to find out what minimum requirements your ride must meet to be street legal -- are you required to have side mirrors? Must your bike have a speedometer? Be sure to check out all the requirements before you get too involved in your creation, or it may be banished to a corner of the garage.

In the next section, we'll take a look at some of the famous bike shops in the United States.

Motorcycle lovers are living in a great era -- they have a wealth of choices from some of the best builders ever to work on a bike. A few bike shops from the good old days of the chopper are still around, but many more got their start in the '90s. Here's a small sample:

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There are hundreds of other custom bike shops in the United States. If you decide to have a shop custom-build your bike, it's important to look into their reputation. Try to talk to some other customers to find out what their experience was like, and see if any reviews pop up on the Internet.

Of course, you can always choose to build your own bike. There are plenty of Web sites out there that sell all the parts you'll need to design and build your own creation, from frame to engine. Building your own bike can be challenging, but it also means that your ride will have your own personal touch. Make sure you do plenty of research and that you assemble the pieces in a dry fitting at least once to be sure everything fits together properly -- you don't want to go through all the trouble of getting all your parts together only to find out at the last second that they don't fit.

Choppers are all about individuality, yet they also seem to foster feelings of community within the biker world. Many chopper owners like to ride with large groups of other bikers. Some even consider riding a focal point of their lifestyle, setting aside time just to ride. The chopper appeals to riders' senses of nostalgia, danger, mystery and freedom, and that isn't likely to change anytime soon.

To learn more about choppers and related subjects, follow the links on the next page.