What's Cool In Road Cycling

CompuTrainer Co-Founder Chuck Wurster Interview

As co-founder of CompuTrainer, Chuck Wurster has not only seen it all in the world of power-based cycling trainers, he’s had a hand in the creation of a category that most of us take for granted today.  Chuck talked candidly about what makes CompuTrainers better than any other trainer available.


I bought my first windtrainer second hand for about $30 in the late 1980’s. It made so much noise when I wound it up in my living room, that the girls who lived downstairs knocked on my door to see what all the racket was about.  Remember those days?

Indoor training has come a long way.  CompuTrainer was there at the very beginning, creating the world’s first wind trainer, and then evolving it into a quiet, power-based trainer that’s been used by champions and athletes the world over.


Chuck Wurster was there at the beginning too.  As sales & marketing head of the Seattle-based RacerMate, he’s been part of the company’s leadership for 40 years.  Although the software powering CompuTrainer has evolved constantly to deliver the most useful data for indoor training, the CompuTrainer still looks much like the original version – a tribute both to its design integrity and the company’s no-nonsense commitment to stick with something that works, and not change simply for change’s sake.

Another thing that hasn’t changed is Chuck’s passion for his products.  Talking recently, Chuck was downright fired up about some of the competitors’ advertising claims relating to “the most realistic feeling” and “most accurate” trainers on the market.

So I suggested we tee up this interview so Chuck could tell us why CompuTrainer is the most accurate and reliable trainer there is.


In The Beginning
PEZ: How did RacerMate get started, and how was the CompuTrainer invented?

Chuck: RacerMate was formed as a wholly owned subsidiary of FloScan Instrument Company, Inc., of Seattle, WA in 1975. The initial purpose of RacerMate was to commercialize the world’s first Bicycle Wind Trainer which RacerMate’s president, Wilfried Baatz, had invented. At that time the only device for indoor bike training was rollers whose use was restricted (as it still is today) to cyclists with advanced cycling skills who can balance on the rollers without crashing. The Wind Trainer required no special skill and could be used by anyone who wanted to train indoors. But most importantly, the load that it generated was essentially identical to the wind load that a cyclist experiences when riding on the road at any speed. At the time this was a remarkable improvement in indoor bike training which the cycling public was quick to take advantage of. Within a few years RacerMate was manufacturing more than 25,000 wind trainers annually.


The first wind-load trainer by RacerMate.  (Even the way they spell their name has evolved.)


Chuck:  …The only disadvantage of the wind trainer was the noise it produced. This gave rise to the development in Japan of the magnetic trainer which drastically reduced the noise levels. The magnetic trainer, although quiet, had a totally unrealistic load curve which was opposite to the wind load curve which cyclists experience in real life. It turned out that indoor cyclists cared more about trainer noise levels than they did about realistic loads – as magnetic trainer sales grew and wind trainer sales declined.

It was in response to the rapidly rising popularity of the “low noise” magnetic trainer that RacerMate conceived the CompuTrainer – this was in 1986. The idea was to utilize electro-magnets instead of the fixed magnets used in the magnetic trainer. By varying the electrical current to the electro-magnets it would be possible to vary the load generated so that the user experiences both low noise AND realistic loads – the ideal combination.

By varying the load electronically it was possible for CompuTrainer to accurately simulate the loads that a rider experiences on the road based on all the relevant variables – the weight of his body and bike, the road grade, the bike speed, and the wind speed.


The Gold Standard
Pez: You refer to CompuTrainer as the Gold Standard – so what are CompuTrainer’s strongest attributes, and why does it deserve such a lofty accolade?

Chuck: When we refer to CompuTrainer as “The Gold Standard” it’s because it provides the best technical performance of any electronic trainer on the market. That means that it has highest accuracy, the highest repeatability, and the longest life of any trainer on the market. Its accuracy & repeatability have been substantiated in peer reviewed laboratory studies published in scientific journals like the American College of Sports Medicine and the International Sports Medicine Journal. In the ACSM study a representative group of CompuTrainers demonstrated repeatability of 0.8%, better than the 1.0% level considered essential to qualify for serious sports science use. No other electronic trainer meets this standard.

When referring to repeatability it’s also important to consider the time period involved. Annual CT performance measurements at the Peak Centre for Human Performance in Ottawa, Canada, have confirmed that CompuTrainer repeatability is within +/- 1% for upwards of 5 years. This outstanding result makes CompuTrainer particularly well suited to studies of performance improvement over time. Cyclists and triathletes who use CT to track their performance over many years, even decades, report gains into middle age and a reduction in subsequent declines.

I know of athletes who use their CT’s continually for 5, 10, 15, and even 20 years. In commercial MultiRider studios it is not unusual for CT’s to operate for 7-8 years of heavy use.

Remember magazine ads?  Here’s one from the late 1980’s – and check out the “big” players in the indoor trainer marketplace.


And Repeat
Pez: It makes a lot of sense that repeatability is a major issue, since measuring power gains (or losses) can only be valid against a baseline standard that never changes and that can be referred to as long as the athlete is training and tracking their progress – which could be for many years or even a lifetime… Why is CT so repeatable over the years?

Chuck: CompuTrainer’s laboratory standard repeatability is traceable to its proprietary Eddy Current Brake design; its unique, extremely robust mechanical construction; its use of the highest quality mechanical and electronic components, and our attention to maintaining close control of dimensional tolerances. Fundamentally, nothing in a CompuTrainer changes over years of operation so there is little to affect its short or longterm repeatability. A well-designed Eddy Current Brake design (which controls the resistance), unlike trainer designs which depend on ‘strain gauge’ technology, is unaffected by the passage of time.

It goes without saying that to meet our stringent accuracy and repeatability specifications CompuTrainers must be tested using the most accurate and reliable method there is.  In the field of bicycle science this means using the “first principles dynamic bicycle dynamometer”.  We have three such dynamometers of our own design and manufacture which are used to test and calibrate every CompuTrainer (and Velotron) coming down the assembly line.   The best that bicycle science has to offer for research has always been a standard part of the CompuTrainer production process.

CompuTrainers are used around the world at multi-rider studios.


Real World Feel
Pez: Reproducing the feel of ‘real world’ cycling on a trainer has long been a battle ground for various trainers and their marketing people. Are CT’s physics the only physics of any trainer that duplicate the real world? And how important is this?

Chuck: You’ve asked a really crucial, important question. If your bike trainer exactly duplicates the loads you experience on the road in every respect then your neuromuscular system is also being recruited identically. In that case any improvements you achieve indoors on your trainer will also occur on the road. The whole trick is to duplicate road cycling conditions indoors on the trainer as closely as possible.

All electronic bike trainers have software physics algorithms that establish the loads that the rider experiences. Ideally the physics algorithms create loads that exactly duplicate the loads experienced on the road. That is exactly what happens with CT – and has been from the very beginning. BUT, it does NOT happen with any other bike trainer! Why not? Because no other trainer has physics algorithms software which generate the retarding effect of the inertia (weight) of your body and bike. On the road the rider must exert more force in order to accelerate his body and the bike. On CT the physics algorithm creates that additional force. Other trainers DON’T. That’s why riding a CT feels (and IS) the closest thing there is to riding on the road. Performance improvements achieved on a CompuTrainer transfer directly to the road.

You don’t have to be mathematician or physicist to prove that CompuTrainers create the effect of inertia. Just get on your bike and accelerate it to 20MPH on a level road on a calm day. It will take around 10 seconds depending on your weight and strength. Do the same thing on a CT after entering your body and bike weight and a level grade; the acceleration time will be close to the same 10 seconds. And, as it should, doubling your weight will double the acceleration time, and halving your weight will halve the acceleration time. Repeat this test on ANY other trainer and the acceleration times will be grossly different proving that their physics algorithms are wrong.

There’s another element of rider inertia which the CT firmware creates and other trainers disregard. Each turn of the crank contains periods of acceleration which must be measured and accounted for by the physics algorithm to create the correct load at every point of the pedal stroke. CompuTrainer does this, but other trainers don’t.



CompuTrainer was the first to introduce pedal stroke analysis, which you called SpinScan.  What is it and why is it so important?

Chuck: SpinScan analyzes the rider’s pedalling efficiency, which is displayed both graphically and numerically – allowing riders to see any imbalance between their leg power, and efficiency.  By using SpinScan the rider can train his neuromuscular system to  smooth his pedal stroke to achieve higher pedalling efficiency.  This results in higher speeds at the same power output – in other words,  improved performance.   Practicing improved pedalling technique with SpinScan is an important reason why CompuTrainer users achieve big speed gains.



How does the CT stand maintain its absolute structural integrity?
Chuck: The CompuTrainer stand is based upon the use of Steel Investment Castings which give it immense strength, unparalled dimensional rigidity and stability, and ample hand clearances to protect against accidental injuries. The ball-bearings are the highest quality aircraft bearings available to maintain minimum friction operation over a long life. Their alignment is guaranteed by using a single metal structure machined to dimensional tolerances of +/- 0.0002 inches.


PEZ: I first rode the Velotron several years ago and it’s one of your most impressive pieces of training gear – that 55lb fly wheel is the largest available for cycling consumers.  How does the Velotron fit into the RacerMate product line?

Chuck: The emergence of CompuTrainer led to considerable interest from sport science researchers who need a bicycle ergometer possessing the highest possible levels of accuracy,  repeatability, and rangeability.    A research ergometer design does  not have to meet the size, weight, and portability restrictions that apply to the CompuTrainer, and price is not as important.   Free of these restrictions, RacerMate created the new Velotron eddy current brake ergometer which has since set the worldwide performance standard for research bicycle ergometers.   Its power range from 5Watts to 2000Watts uniquely covers the entire range of human capability.  Repeatability is a matchless +/- 0.2% across the range.   Worldwide, more than 600 sports science research studies at universities and sports science facilities  have been published based upon Velotron power measurements.


Pez: Do the professional cyclists and triathletes use CompuTrainer?

Chuck: The race results of athletes using CompuTrainer are really unprecedented. During the past 11 years there have been 16 podium sweeps by our pro triathletes in major races (even though a single sweep is an otherwise unheard of occurance). At the recent Ironman 70.3 South American Championship in Brazil our men swept the podium; the women’s champion is also a CompuTrainer veteran.

CompuTrainer has been the favorite bike trainer of hundreds of professional triathletes since it first became available. Of the 13 men and women elected to the USA Triathlon Hall of Fame, over half trained exclusively on CompuTrainer. CompuTrainer plays such an important role in the careers of many pro champion triathletes that they do all of their bike training on it and ride the road only on race day. Current Ironman champions Andy Potts and Lionel Sanders are good examples. Current Xterra World Champion Josiah Middaugh has depended on CompuTrainer for his entire career. The same is true of Kate Bevilaqua, the first woman overall winner of an Ultraman race ahead of all the men. Kurt Searvogel recently broke one of the oldest cycling records in the books set in 1939 by riding 76,000+ miles in one year; he is a longtime CompuTrainer user.



Join The Gang
Pez: Multi-rider training sessions have become commonplace now, but long before people were using the web to connect and ride with cyclists anywhere in the world, CompuTrainer introduced it’s own multi-rider training sessions, where riders could train together on the same course at the same time.  How has it grown over the years?

Chuck: The impetus for CompuTrainer MultiRider originated in 2003 in the Boston area. A local triathlon club, Team Psycho, had developed a popular winter event using eight CompuTrainers paired up with 4 computer monitors ; at the time the CompuTrainer software was limited to 2 rider competition. RacerMate saw the opportunity to create special multirider software to allow all 8 riders to race against each other by connecting them to a single computer/monitor.

The new CompuTrainer MultiRider software for 8 riders quickly gained a following. The accuracy and rugged durability of CompuTrainer has supported the rapid growth of MultiRider indoor cycling studios around the world. They number in the hundreds and are operating commercially in the U.S., Canada, Australia, New Zealand, South Africa, England, Ireland, France, China, Singapore, Costa Rica and Dubai.


Total Recall?
Pez: RacerMate recently recalled the CompuTrainer Blue Flywheels manufactured before 2008. What is the problem with the Blue Flywheels that required their recall?

Chuck: Blue CompuTrainer Flywheels refer to the cast zinc flywheels made before 2008 which were painted blue. From 1997 to 2007 several batches needed to be stripped and repainted due to a paint finish that was not up to our standards. A chlorinated chemical solvent was used to strip the paint from the flywheels, which, over many years interaction between the chlorine and zinc caused it to eventually disintegrate. Nothing like this had ever been heard of and as far as we know it may never have been previously experienced. It came as a complete surprise, and our voluntary recall was the result. Anyone reading this who has a CompuTrainer blue flywheel needs to contact us for a free nickle plated steel replacement flywheel. It will last forever!


Thanks to Chuck for taking time to speak with us, and you can find more info about their products at the website CompuTrainer.com, and Velotron.com.

• Get the best price ever on a CompuTrainer at their SUMMER SALE – US$1099.00 on now.


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