KGS Bikes Fitting vs. Retul - The Difference Between a Fitting Tool and a Fitting System

I recently received a call from a client in Dallas who noticed that one of the local stores is installing the Retul 3D Motion Capture System and wondered if it was better than the fitting she received from KGS Bikes. The explanation is a little more involved than a Q&A question so I decided to bump my scheduled ezine article for this one.

The KGS Fitting System, those by Serotta, WobbleNaught, Carmichael, Specialized, Cyfac, Body Scan, Fit Kit and others, use a procedural system that gets a specific outcome and these may or may not even use the data generated by a motion capture system.

Retul has become the gold standard in fitting tools in the past 18 months. The reason I say it is a fitting tool is that Retul can be used with any fitting system. It is 3D Motion Capture System that can accurately measure sensor points which are attached to rider or are indexed to a bicycle.

Retul has a competitor in Dartfish, which is a 2D motion capture system that I own. I am planning on purchasing Retul to augment my fitting services so here is an explanation of how I deal with fitting systems and motion capture systems. The crosshair laser that I use to measure bicycles is another reference tool that is independent of the fitting system. It helps to separate the two as there is overlap and thus room for confusion.

Fitting Systems - KGS vs others. Many of the fitting systems on the market today feature equations or benchmarks that a rider should use to calculate the best way to fit a bicycle. Fit Kit is one of the earlier systems that use a plumb line to determine Knee Over Pedal Spindle, WobbleNaught uses 33 different measurement points of the rider and the bike to get a computer generated setup for that individual rider and that individual bike. Carmichael uses angles and geometry to assure that an individual is set up within an acceptable range of angles on the bike. Serotta and others use a combination of measurements and riding on either the owner’s bike or a setup bike.

What separates the KGS Fitting System from the others are two specific processes:

1) I have developed a system of finding the best, most efficient and balanced position for an individual using my custom setup bike, through scientific analysis using a step by step approach to find that perfect setup whether the rider is young or old, fit or unfit.

2) The use of a setup bike with a power meter, that is 100% infinitely adjustable and capable of producing the workload that you as the rider really produce on the road, is critical. My system determines a proper bike setup, rather than a setup based on the limitations of a specific bike.

Fitting Tools - Setup bike. The setup bike was just described and is the core of my fitting system. It has road, mountain and time trial handlebars, different saddles, adjustable cranks from 150-230 mm and almost all modern pedal systems. Since the bottom bracket is the datum point, every other conceivable position is determined by the location of the saddle and handlebars. Since all riders interface with the bike in exactly the same place, (pedals, handlebars and saddle), if the setup bike is able to be positioned to find the rider's best position it can be found, documented and repeated.

The setup bike is not the system any more than one's bike on a trainer would be. In fact, my system is good enough to find the perfect setup even if it would be difficult to build a real bicycle with those specifications. This is because I don't assume that the bicycle industry has created a stock frame for you, I assume nothing. When we get through the fitting process we know exactly how to build a frame that is perfect for you, or to specify a stock frame that works with your body.

Cross hair laser - This fitting tool is what I use to accurately measure the handlebars and saddle relative to the bottom bracket. These lasers do nothing but project two lines into space, but the accuracy attainable from this device is fantastic.

Dartfish Advanced Video Analysis - I bought the Dartfish software and used it with my fittings for a few years but found that the only thing that really worked well was the ability to show ankle placement and the time it took to show the client problems was better spent in showing a solution rather than highlighting the problem. Dartfish is a great tool and some clients can benefit from it but most are better off letting me show them how to get better form rather than see how bad their form is in the first place.

Retul - The Retul system is a 3D motion capture system. The reason I am getting one is the ability to capture the fitting session and not only save that data but analyze it with other setup data. I have the ability now to get people setup properly on the bike. That is not the point. Having a system that gives me better resolution of all the aspects of a rider's position and being able to save it is important. Another part of the Retul system is a sensor that can be triggered when it touches parts of the bike so the critical dimensions of the setup bike can be captured more quickly and with the same accuracy that I use now. I can save a few minutes doing documentation which usually means I get more time to spend helping the client with specific problems.

In summary, a bad fitter will not do a significantly better job with Retul. All the fitting procedures and knowledge that the fitter used prior to the acquisition of Retul are used after the device is purchased so many bike shops are still stuck with the age old discovery: Bike fitting is not easy.

It has taken me years of study to get really good at bike fitting and I still learn things every day. I feel lucky to have a studio that I can use to really do a client some good. I can't speak for other shops and studios, but I work not only hard but as smartly as I can to put the client first and get an awesome outcome. I can't wait to get my own Retul system but the fact that I just have my knowledge, skills and setup bike means that current fit clients will get what they want and need, which is a custom setup that works for them.

At the end of the day, I still find a lot of stock bikes don't fit grownups well. It is irritating as I have a lot of educating to do when people find out that it is not they that are abnormal, but the bike they want to buy that may not be the one for them.