Butt out! Frame butting

When it comes to crafting bike frames, manu­facturers have more tricks up their sleeves than just changing the frame material. Engineers have come up with a variety of ways to manip­ulate strength and rigidity of frames, including changing the tube width, the thickness of tube walls, and the tube shape.

Butting is one such technique. It’s the process of making one part of a tube thicker than another part of the same tube. This is usually done on the inside walls of the tube, so the outside — the part that you see — is all the same. The thicker part of the tube provides strength where it’s needed more, and the thinner part of the tube helps reduce weight. Single-butted tubes have one side of the tube that’s thicker than the other. They’re often found on seat tubes where the thicker part of the tube is attached to the bottom bracket to provide support against the force of pedaling. Double-butted tubing is thin in the middle, where less strength is needed, and thicker on both ends, where the tube connects to other tubes. On some frames, manufactur­ers may even use triple — or quadruple-butted tubes.

Waxing your frame

Waxing is not only a great way to keep your bike looking shiny and new, it’s effective at keeping rust at bay. Give your bike a thorough waxing as a part of your annual overhaul, when the frame will be more accessible. If you ride a lot, think about waxing the frame every few months.

Although there are a number of waxes designed for bikes, any all-purpose car wax should do the trick.

Suspended in Disbelief: The Suspension

In the continuing trend toward bikes offering a more comfortable ride, suspension has played a leading role. Riding a bike without suspension on a rough road makes you feel like you’re the shock absorber. Every road or trail shock that hits a stiff rigid bike is transferred directly into your arms, legs, and the rest of your body. Not only that, but if you hit something on the road or trail with enough force, the bike may stop suddenly and send you flying like Superman.

On a bike with suspension, when you hit a pothole or run over a rock, the shock absorber dissipates the force before it’s absorbed by your bike and body. It improves safety, comfort, and riding efficiency (because you won’t have to hover over your seat to act as your own personal shock absorber). Bicycles with suspension are safer because they give you more control of the bicycle — the wheels stay in contact with the ground more and you don’t get bounced around on the trail as much.

The main idea behind suspension is that the coiling of a spring keeps you float­ing or suspended when you ride. This provides the bounciness or springiness of the suspension. The second idea is that the bounciness of the spring is better suited for a bike if it can be controlled or dampened. A spring with too much bounce will make you feel as though your bike is attached to a pogo stick.

Suspension is generally found on four places on a bike:

✓ Fork

✓ Stem

✓ Seat post

✓ Rear axle

Types of suspension

Most suspension systems use some type of spring to absorb impacts from the road. Generally, three types of springs are used:

✓ Coil: Coil springs are made from steel of different gauges and are the most popular type of spring.

✓ Air: Air maintained inside a sealed chamber acts as another kind of spring.

✓ Elastomer: Elastomers are made of urethane and aren’t as common these days as they were in the past.

Suspension works best when a spring is paired with some kind of damp­ing system. Damping is the ability to slow the rebound of the suspension. Rebound is the speed at which the suspension returns to its original position after it has been compressed. And compression is the amount of time it takes for the suspension to absorb your weight. If your suspension has unchecked rebound, you’ll feel like you’re riding a bouncing ball. If your suspension has the bouncing-ball feeling, adjusting the damping can reduce the speed at which the suspension compresses and rebounds.

Air and oil are two types of damping systems. In an air-based damping system, air pressure is adjusted to change the amount of damping. In oil — based damping systems, a piston flows through a volume of oil. Adjusting the size of the hole in the piston changes the amount of damping.

Many suspension systems have adjusters that allow you to change the amount of damping and preload (the amount of compression applied to suspension before it supports any weight). By preloading the suspension, it will sag less and give you a stiffer ride. Reducing the preload will cause the suspension to sag more. On many suspension forks, the preload adjuster is found on the top of the fork and the damping adjustment at the bottom of the fork.