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Expert Advice - Cycling Sizing / Safety

Rim/Tire/Bike Sizing 101
Safety Equipment
Bike Helmets


Choosing The Right Rims

The rim is the outer part of a wheel that, along with the hub and spokes, supports the tire.

  • Rim size
    • Rims come in various sizes and materials
    • Rim sizes for road and hybrid bikes are usually 27-inch or 700 centimeters
    • Most mountain bikes have 26-inch rims
    • BMX and freestyle bikes have 20-inch rims
  • Rim width
    • Rim width will vary depending on intended use
    • Some rims are designed to accept a few different tire widths
    • Road and hybrid bike rims are narrower than mountain, BMX or freestyle bike rims
    • Narrow rims are lighter and offer less rolling resistance, whereas wide rims are heavier but offer greater durability
    • Rims can be made of steel, aluminum alloy, heat-treated alloy, carbon fiber or, at the extreme high-end, can consist of other expensive, space-age materials
    • For most types of riding, aluminum alloy rims offer the best value because they are light and absorb road shock
  • Quick-release wheels
    • Quick-release wheels are wheels that do not require tools to detach from the bike
    • They are particularly handy if you have to change a flat tire or transport the bike in a car


Choosing The Right Tires

Tires greatly influence a bike's riding characteristics, since they directly affect traction, steering and braking. There are two basic types of tires clincher and tubular.

  • Clincher
    • Refers to a conventional bike tire with a separate inner tube
    • When inflated, the tire clinches the rim as its inner edges, called the bead, become captured against the rim walls
    • Most road and all mountain, BMX and freestyle tires are clincher
  • Tubular (or sew-up)
    • Refer to a tube that is sewn into the tire, and then the tire is glued onto a special edgeless rim

How To Size A Bike

The type of riding you plan to do will determine the style of bike you choose, which in turn will dictate the frame size and components you will need. The most important part of buying a bike is finding one that fits you.

Determining your proper frame size

Frame size is not dependent on your overall height. Rather, it is more a matter of leg length. Here are some starting points to help you determine if a particular bike is within your size range.

Frame height

  • Generally speaking, when sizing a diamond frame bike, sometimes called a men's or unisex frame, you need to measure how it will fit when you straddle the top tube while flat-footed in the shoes you'll be riding in. So measure your inseam from the bottom of your feet to your crotch.
    • For a road or hybrid bike, you should have an inch or two of clearance between your crotch and the top tube
    • For a mountain bike, clearance should be about three inches--especially if you'll be riding in rugged terrain where an unplanned dismount is likely
    • BMX and freestyle bikes all have 20-inch wheels, so frame size isn't really an issue. A rider's physique and riding style is accommodated by choosing the appropriate seatpost, stem, handlebar and crankarm lengths.
    • When considering a women's frame, or frame with no top tube, clearance isn't an issue. In this case, the best fit is usually determined by reach.
    • Frame sizes come in inches or centimeters, depending on the manufacturer
    • Not all manufacturers measure from the same points on the frame. Some measure from the bottom of the crankset to the top of the seat tube. Others may measure from center to center, bottom to center, or some other angle.
    • Also, not all frames have the same geometry. All of this means that a 21-inch frame from one company may fit very differently than the same size from another manufacturer.


  • Finding the right reach (the distance from the seat to the handlebars) is important for both comfort and control
  • As a rule of thumb, when you sit on the seat with your feet on the pedals and your hands on the handlebars, the handlebars should block your view of the front hub. You shouldn't be stretched out like Superman or sitting upright.
  • Be sure you have at least a slight bend in your elbows no matter what style of bike you choose
  • Locked elbows (caused by too-long reach) are a frequent cause of shoulder, neck and back pain
  • If you feel scrunched up and your elbows are in your ribs, the reach is too short
  • If the top tube is slightly too long or short, reach can usually be adjusted by changing the stem length - the stem being the part that connects the handlebars to the steering tube

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