The Perfect Fit — Bike Fit Basics

By REI staff

In This Article

• Two Steps to a Good-Fitting Frame
• How to Measure Yourself
• Simple Adjustments, Perfect Fit

Bikes should be comfortable to ride. But if you think that a cushy ride comes only from spring-loaded, doublewide seats and shock-absorbing handlebars, read on.

The Basic Ingredient

A comfortable, perfect-fitting bike means your skills will improve immeasurably as you go out and enjoy each ride. And it all starts with the frame. Handlebars, stems and saddles can be swapped out or adjusted to create a better-fitting bike. But getting the frame right is the important first step.

Two Steps to a Good-Fitting Frame

Step 1 Get the Frame Height Right

You'll need a coffee-table-type book and a tape measure for this. Got 'em? Now stand against a wall with your feet about 8" apart. If your shoes are on, take them off. Put the book between your legs, comfortably up against your crotch. Make sure the spine is parallel with the floor. With the tape measure, determine the length from the spine of the book to the floor. This is your inseam measurement. Write it down. You'll need it later on.

When standing over the top tube of a bike (the tube that runs roughly parallel to the ground), you want some clearance between that tube and your crotch. It breaks down like this for both men and women:

• Road bikes— 1" to 2" of clearance; 2" or more for aggressive riders.
• Mountain bikes— 3" to 5" of clearance; 4" to 5" for aggressive riders.
• Commuter, touring and kids' bikes— 2" to 4" of clearance.

REI includes a sizing chart with each bike we feature online. The chart includes the stand-over height for each frame size of that particular bike. The distance between your inseam and the stand-over height should fall within the range listed above.

Inseam – clearance = stand-over height.

For example, if you have an inseam of 34", and you're buying a mountain bike, you'd want a stand-over height of about 31".

If the bike has a sloping top tube, as many women's bikes have, you'll want to measure the clearance from an imaginary top tube (pretend the top tube extends horizontally from the front of the bike), and measure from there. REI includes this imaginary line as part of its calculation of stand-over height.

Step 2 Get the Frame/Top Tube Length Right

If a bike is too short or too tall, the seat can usually be adjusted to compensate. The same is true for the length. Simple changes in handlebar height stem length and fore/aft saddle adjustments can help fine-tune your bike's fit. Still, finding the right length is important.

Play the Piano: Sit on your bike and grip the handlebar. A proper tube length will put your back at a 45-degree angle with your arms relaxed and comfortably bent at the elbows. This position absorbs the bumps and vibrations delivered to your bike by the road or trail. You should feel like you could play the piano on your handlebars. That is, you're not bent so far over that you need your arms to keep you upright. This is true for all types of riding except that of hardcore road racers. To get the ultimate in aerodynamics and power output, racers prefer nearly 90-degree back angle.

Comfortable Geometry: If you're unable to sit on the bike because you're ordering online or buying the bike as a gift, pay close attention to the stand-over height. Most bikes come with a comfortable geometry, but you may need to make some adjustments to the seat and handlebar positions. The top-tube length of a bike can be found in the sizing chart for each bike. Two other measurements can be used to help determine the top-tube length that is best for you. By measuring the length of your torso and the length of your arm and adding the two together, you can arrive at a rough estimate of the top-tube length you need. (See sidebar.)

How to Measure Yourself

Torso: Seat a coffee-table book against your crotch with the spine parallel to the floor. Measure from the spine of the book to the little V in your throat just above your sternum. This is your torso length.

Arm: Find the end of your collarbone. Grip a pencil in your fist and measure from the pencil to the tip of the collarbone. This is your arm length.

Add the 2 measurements together, divide by 2 and subtract 6" from the total.

(Torso length + arm length) / 2 – 6" = rough top-tube length

For example, if your torso is 29" and your arm is 26.5", the top-tube length that would best suit you would be about 22". It looks like this:

[(29 + 26.5)/ 2] – 6 = 21.75

You can go about 2" longer or shorter on the top-tube length with this formula. Adjusting the seat and the handlebars generally compensates for the 2".

NOTE: Use inches for all measurements.

Other Factors to Consider

• Children, especially girls, tend to have long legs and short torsos. For them, the stand-over height is more important than the top-tube length. When buying a bike for children, the most important factor is that the bike should not be too large. A large bike can become unwieldy in their hands and lead to a loss of control as well as confidence.
• Women are generally taller in the legs and shorter in the torso than are men. REI offers women's models that are specially designed with a shorter top tube to accommodate this body type.
• However, it's possible that the frame sizes offered on our bikes still don't fit you. The stand-over height may be too short or the top tube length too long or vice versa. If this is the case, choose the next smallest frame that will fit you. From the smaller frame, you can adjust the seat, stem and handlebars to achieve the perfect fit.

How do you adjust the seat and handlebars? Read on!

Simple Adjustments, Perfect Fit

Once you have your bike in hand, it's time to get the fit dialed in. Handlebars can be swapped, saddles adjusted, gearshifts moved, all to create the very finest biking experience.

Listen to Your Body

There are no indisputable rules for adjusting your bike to fit your body. The formulas serve as a good gauge, but the right fit for you will depend on your body shape and how you like to ride. To get the right bike fit, you have to do 2 things:

• Experiment— As you ride your new bike, try different setups before you decide on one. Ride with your seat slightly forward or your handlebar a little higher, then switch things around.
• Be aware— Pay attention to any aches or pains that develop as you go. For example, a cramped back may be telling you to raise your handlebars slightly, while sore knees may be telling you that your saddle needs adjusting.

The following fit suggestions are general guidelines only. They'll provide a good starting point for you to fine-tune your bike fit. After that, feel free to make your own adjustments in response to your needs. And remember, if you have trouble finding the right bike fit, you can always take your bike in to a full-service REI bike shop and discuss your problems with one of our trained bike technicians.

"Pedal backward with your heels on the pedals. Your heels should just lose contact with the pedal at the bottom of the stroke. Also, make sure when you do this that you're not rocking your hips." — Lee Miller, Bike Specialist, REI Seattle store

Check Your Saddle (Seat) Position

Saddle position is largely a matter of personal preference. But, as it affects your body while riding, it's important to find a position that works well.

• Saddle height: Correct saddle height can lower the stress on your knee joints and give you a more powerful pedal stroke. Your saddle should be high enough that your legs almost (but not quite) fully extend at the bottom of each pedal stroke. To check for correct leg extension, rotate your pedals to the 12 o'clock and 6 o'clock positions (while sitting on your saddle). The leg touching the 6 o'clock pedal should bend slightly at the knee when your foot is in its regular pedaling position.

  To move your saddle up or down, loosen the binder bolt (or quick-release lever) located at the top of your seat tube — the somewhat vertical frame tube that your seatpost slides into. Slide the seatpost up or down in the seat tube as needed, being careful not to raise it beyond the "minimum insertion mark" etched into its side. Retighten the binder bolt or quick-release lever securely before riding.

• Saddle tilt: There is no such thing as a correct amount of saddle tilt. Some cyclists prefer a forward tilt. Others prefer a backward tilt. Still others like their saddles completely level. To find a tilt position that works for you, take a few test rides and experiment with different setups. To make saddle tilt adjustments, simply loosen the binder bolt at the top of your seatpost (directly underneath your saddle) and make your adjustments. Be sure to retighten the bolt securely before riding.
• Saddle fore/aft position: The fore/aft position of your saddle can have a significant effect on your body position while you ride. To check for correct fore/aft position, sit on your saddle (using a friend or a stationary object to keep yourself balanced) and rotate your pedals until they are horizontal (at the 3 o'clock and 9 o'clock positions). If your saddle is positioned properly, the small bony bump just below your kneecap should line up directly with your forward pedal axle. To check this, simply hang a piece of string with something tied to one end (like a pen) from the bump. The string should hang down directly over the pedal axle. If it doesn't, make adjustments by loosening the seatpost binder bolt and sliding your saddle forward or backward. Be sure to retighten the bolt securely before riding.

Check Your Handlebar Position

To find the handlebar height that works well for you, start with your handlebar stem about 1" lower than the height of your saddle nose. If your lower back starts hurting and you want a more upright body position, raise your handlebars slightly. If you find that you want a lower, more aerodynamic position, lower the handlebars slightly.

On a road bike, switch your hand positions from the handlebars to your brake hoods to the handlebar drops (if you have drop-style bars) from time to time. Find a handlebar height that is comfortable no matter where your hands are positioned.

For a mountain bike, decide which terrain you'll likely ride over 80% of the time. A rider who likes downhill-style riding may want a higher handlebar or "riser" bar, while a cross-country rider will want a lower handlebar for climbing and technical riding.

In both cases, make sure that you can wrap your fingers around your brake levers quickly in case you need to apply maximum braking power fast.

To adjust the height of your handlebars on a road bike:

• Loosen the stem expander bolt located at the top of your handlebar stem (the bolt head should be clearly visible) until it's about 1/4" above the top of the stem. Be careful not to loosen this bolt any further, or the expander nut (hidden inside your stem) may fall into your frame.
• Tap the top of the expander bolt sharply with a rubber mallet (or place a block of wood on top of the bolt and use a regular hammer) to loosen the expander nut inside the stem. This should allow you to rotate the handlebars easily and move the stem up or down (as you hold the front wheel in between your knees). Reposition the stem and handlebars up or down as needed, then retighten the stem expander bolt firmly. Be sure not to raise your stem beyond the minimum insertion mark etched into its side.

If your bike has cantilever brakes, you might have to readjust your front brakes each time you reposition your handlebars. To learn how to perform this adjustment yourself, pick up one of our great at-home bicycle maintenance books.

NOTE: Most mountain bikes come equipped with an AheadSet® system. The stem height on these systems cannot be adjusted. To raise or lower your handlebars, you'll have to choose a new stem or a different set of handlebars or both. AheadSet stems typically come in 90-, 40-, 20-, or 10-degree angles to accommodate various styles of riding.

The Cockpit

The space created by your arms and your handlebar is considered your "cockpit" space. You don't want to be too crowded or too stretched out in this space. Saddle adjustments will solve most cockpit space problems but you may also need a wider or narrower handlebar. It's best to let a bike shop handle this adjustment or parts-swap for you.

You should now have a bike that fits comfortably and will provide you with years of enjoyment. There's only one thing left to do — that's right — get out there and ride!

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