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Choosing a Mountain Bike 

By Cody Waite

mountain bike The bike leg of a typical off-road triathlon can make up over half of the overall race duration and often determines who will finish on the podium and who will finish at the back of the pack. Even more so than on-road triathlon, the bike leg in an off-road triathlon is critical to your success and the bike itself plays a big factor in this equation. Mountain bikes come in all shapes and sizes. Beyond fatter tires and flat handlebars there are several other factors to consider when selecting a mountain bike for off-road triathlon racing. The most important are:

  • Suspension
  • Tire Selection
  • Wheel Size
  • Gearing
  • Weight

Suspension: Less is More

The majority of mountain bikes sold today are full-suspension mountain bikes, meaning both the front and rear wheels have some form of suspension travel. Suspension has many benefits including increased control and comfort as well as improved traction and less rider fatigue. The amount of travel found on mountain bikes ranges from 3 to 8 or more inches of travel. Suspension travel refers to exactly how much your wheels can move up and down when going over rough terrain. As travel increases in bicycle design the geometry of the bike changes as well as rider position and an increase in weight of the bike. Many experienced riders prefer a bike with only front suspension and no rear wheel suspension (aka hardtail) claiming the lower weight and no rear wheel movement provide a “racier”, more nimble feel compared to a suspension bike. This is purely a personal preference however, as it is all but proven that a standard 26-inch wheeled full suspension mountain bike is faster and more efficient than a hardtail.

For off-road triathlon racing you want to stay in the “cross-country” category of mountain bikes which includes bikes in the 3-4 inch travel range. This category allows for enough suspension for the types of terrain found on off-road triathlon courses while maintaining an efficient rider position for climbing hills, riding technical single-track and fast downhills. The next category up in travel is referred to as the “trail bike” category which is the largest selling category of mountain bikes today with 5-6 inches of travel. Trail bikes can work for the occasional off-road triathlete but the added weight along with a shorter and more upright rider position make for slower climbing and acceleration while also making them less nimble for faster riding over varied terrain. Instead, choosing 3-4 inches of travel for off-road triathlon is the way to go.

Tire Selection: No Tubes

The one word you should know is TUBELESS. This is the only option as far as cross-country and off-road triathlon racing goes, arguably the greatest advancement in mountain biking technology since the suspension fork. The tubeless tire set-up has many advantages with pretty much no disadvantages (except maybe a little extra effort to install). The advantages of tubeless tires include the ability to run lower pressure, thus improving ride quality and traction, without the likeliness of pinch flatting a tube. Flats in general are limited to major tears in the tire since the sealant used with tubeless tires will seal most small punctures up to a quarter inch in size. Lower rotating weight can also be achieved if you can run lighter “non-tubeless” tires as tubeless with sealant. You can instantly drop 100 grams per wheel by removing the tube and replacing with two ounces of sealant. However if you are a heavier rider or ride very rough, rocky terrain you will want to stick with true “tubeless tires” that have reinforced sidewalls for greater protection and support.

As for the tire tread patterns, the choice often lies in the conditions of the trails you typically ride. You will want more aggressively knobbed tires for traction in loose, rocky terrain, lower knobs with tighter spacing between them for dry, smoother courses for lower rolling resistance, and tall, widely spaced knobs for muddy and wet conditions. Tire pressures also differ between trail conditions and rider weight, but with tubeless tire set-ups you can effectively run pressures between 20 and 26 psi in most conditions. Incredible!

Wheel Size: Is Bigger Better?

The big debate in cross-country mountain bikes these days is between wheel sizes: the long time standard 26-inch wheel versus the larger 29-inch wheel size. There are arguments for and against both and the official jury is still out. Either size works well for off-road triathlon racing. The 29-inch wheel is gaining popularity amongst both experienced riders and novices alike. The larger diameter wheels allow for better traction due to a larger contact patch with the ground as well as the ability to roll over trail obstacles with more ease while maintaining momentum. The larger wheel diameter performs similar to that of an inch or two of added suspension. A novice rider may find more confidence riding through technical terrain as it seems more manageable and requires less energy than a 26-inch wheel. Trade-offs with bigger wheels are slower acceleration and increased weight due to the increase in mass of the larger wheels and tires.

If a 29-inch wheeled bike is selected, it is even more critical to keep the total weight of the bike in mind as they can become significantly heavier than a 26-inch bike. For this reason, many 29-inch riders opt for a hard-tail frame design (no rear suspension) to keep the weight down and “racier feel” high. It is becoming possible nowadays to have a 29-inch hardtail mountain bike under 20 pounds and even a full-suspension 29’er under 23 pounds, making 29’ers quite possibly the ideal bike selection!

mountain bikeGearing: More Advanced Considerations

Having the right gear ratios when mountain biking is essential. Off the floor mountain bikes will provide all the gears (usually more than) you need to train and compete. Up until just a few years ago the standard gearing on a mountain bike was a triple ring crankset and nine speed cassette in the rear providing a massive range of gears that you may or may not even need or use. Over the last several years cross-country racers have began to adopt a 2x9 system that involves using a two-chainring configuration up front.

By using only two chainrings, often slightly smaller (more compact) than the big and middle rings found on a standard triple crankset, you can improve shifting performance, achieve more “useable” gear ratios, and save some weight. With the introduction of 10-speed rear cassettes for mountain biking, with even larger gear ranges, it is more possible than ever for intermediate level and even beginning riders to benefit from the two-chainring set-up on their mountain bikes. Now it is even becoming popular for some advanced riders to use only a single-chainring up front looking to save even more weight and keep things as simple as possible.

Weight: Light but Durable

When selecting a mountain bike for off-road triathlon racing the overall weight of the bike should be a top priority. Mountain biking involves riding up and down hills of all sizes, over obstacles, around tight corners with frequent braking and accelerations. The lighter your bike, the easier all of these techniques will be to perform. This being said, you never want to sacrifice strength and durability for lighter weight. This is especially true the bigger the rider is riding the bike, so be sure to maintain this strength-to-weight balance when making your bike and equipment choices.

With the strength and durability needed to take abuse, along with suspension and bigger tires the weight of mountain bikes can add up quickly. Often the easiest and most effective area to shed extra weight is in the wheels and tires. Lighter wheels equal lower rotating mass which translates into less power required to move them. Other areas that are often “overweight” on mountain bikes are the saddle, the handlebars and stem, seatpost and pedals. For many, simply replacing these items with lighter ones can drop as much as 2-3 pounds from the weight of their bike with little to no loss in strength or durability. As a guideline, for the average-sized rider, a cross-country bike should fall in the 20-25 pound range.

With these tips in mind when selecting a mountain bike for off-road triathlon, be sure to demo and test ride as many bikes and/or parts as possible to find what works for you. Don’t be afraid to think outside of the box and to and be willing to experiment a little to get that perfect fit and ride you are looking for. There are a lot of options out there and sometimes you don’t know what’s best until you find it. Good luck!

Cody Waite is a Level I USAT certified coach and professional triathlete from Denver, Colo. While specializing in XTERRA, Cody has a background in every distance of triathlon as well as professional cycling. Through his company, Endurance Performance Coaching, he and his associate coaches assist endurance athletes of every ability in improving their own abilities through carefully thought out training and practical education in every aspect of multisport.