Your Bicycle Fitting Guide



bicycle-fitting-guide

I was interested in buying a new bicycle, but I hadn’t been on a bike in over 15 years—ever since a college girl opened her car door into me as I was riding down the Pacific Coast Highway in California. I started talking to Jon Miller, a champion cyclocross master class competitor and national mountain bike racing champion with over 30 years’ racing experience. Jon’s first comment was that the fit of the bike is critical. And after visiting the local bike shop with him, I came to realize it’s more complicated than just being able to reach the ground with your toes while seated!
 

Frames vs. Wheels

Frames are sized according to the distance from the center of the crank to the top of the frame at the seat tube. What makes things confusing is that the units of measurement aren’t standardized. They can be found in metric, American and standard imperial units.
 

Frame measurement

 

Standover height:

if you can touch the ground with flat feet while sitting on the seat, either the frame is too small or the seat is too low. You should be able to fully extend your legs for proper power delivery when pedaling. When straddling a men’s road bike, with a horizontal top tube, flat-footed, you need a couple of inches of clearance between the top tube and your crotch.
 

Inseam length:

Taken from the crotch to the inner ankle, this is measured in inches. Sizing starts at 25 inches and goes up to 35 inches. Inseam combined with height determines which frame will fit best, according to these charts.
 

Wheel diameter

  • – Mountain bikes, regardless of frame size, typically have 26-inch wheels. “29-ers,” with a larger diameter, offer superior ability to roll over obstacles. A 27.5- inch wheel was developed to fill the in-between size at mountain bikers’ requests.
  • – Road bikes take rim size into consideration along with tire size. Without getting into the reasons, depending on if you’re looking at the French code or the ISO standard measurements, for the same tire you’ll see 622 mm diameter (700C) rims. The 650C size has the ISO diameter size of 571 mm. 650C rims are popular with smaller riders and triathletes.

Basically, the tire should fit your frame without rubbing at the fork and it should fit your biking needs as far as terrain. Smaller tires apparently are best only on smooth roads since they have a harder time with potholes.
 

Skinny or Fat Tires?

According to BetterbyBicycle.com, you can ride with more safety, confidence and comfort on wider tires (e.g. switching from 25/28mm to 35-40mm) especially if conditions are slippery or the road surface is rough. But if you’re looking for “zippiness,” then thinner tires are more responsive. It’s just harder to stay balanced on them, so newbies beware. They are also less durable and more likely to pop.
 

Comfort Seat

The height of the seat is adjusted so the heel rests on the pedal and there’s a slight bend in the knee without the pelvis/hips changing angles. There should be about a 30-degree bend in the knee at the bottom of the stroke.

The seat can also be adjusted forward or backward on the seat rail. Pushing the seat back creates more distance to pedal. You may need to drop the seat height.

The saddle should be wide enough so that your weight is distributed on the sit-bones in your rear. You can shop for comfort seats with cutouts for men and women, which off-load the perineum and prevent nerve damage during long periods of riding. Adjusting the tilt angle may help off-load soft tissues too, but be careful since this may cause you to slide forward and push your body out of alignment on the seat.
 

Get a Handle on Things

Your shoulder width determines the size of the handlebars. Think about keeping joints in alignment in the sagittal plane: wrists, elbows, and shoulders. Whether you choose tops or drops depends on how “small” you need to get for efficiency during riding without compromising comfort. Drops do just that—they drop your body so that it’s more streamlined and aerodynamic. Unfortunately, this position is rather hard on the spine and shoulders. Bar extensions (U-shaped) also known as time-trial bars with elbow pads are also for decreasing wind resistance. A compromise is made between aerodynamics and comfort in positioning the back, hips and arms. Ideally you want a 90-degree bend between the biceps and the torso.

The handle bar stem adjusts in length and angle. Working with seat position, torso length, arm length and spinal flexibility, aim for a flat back. The more flexible you are, the bigger the difference there will be in the seat to handlebar height difference. That is, the seat can be positioned higher than the handlebar. Older riders with less flexibility may want the opposite so the handlebars are higher than the seat. And they might need a bar shape that keeps pressure off the wrists, elbows and shoulders by shifting weight to the rear.
 

Quest for a Custom Fit

If you want to scientifically match your body to the perfect bike, then visit a bike fitting specialist trained in Body GeometryTM. A two-to-three-hour session provides you with a comprehensive analysis of your body, your body angles, flexibility, limb lengths and a video of how you ride. These are used to calculate how you ride and the ideal position for you to ride comfortably on a bike that’s adjusted to fit you. Competitive triathletes and cyclists often invest in this service to increase their efficiency along with comfort. However, Body Geometry is also a good choice for those experiencing chronic injuries. Sometimes it’s just a matter of tweaking the angle of a seat inclination or you may discover that you’ve been riding a bike that doesn’t fit.

Jodai Saremi

Jodai Saremi, DPM, BS , is a freelance writer, AFAA certified trainer, and fitness model. She has written for American Fitness, SPIN fitness, Your Health Connection magazines, and other online publications. Her articles have also been featured in textbooks. She enjoys an active lifestyle and lives in Ventura County, Calif. with her husband and two children.

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