Street Bicycles

Bicycle Frame Geometry 101

I was discussing frame geometry with a prominent coach last week and his perspective on frame geometry struck a nerve with me so I wanted to share this topic with you. The nature of my business at KGS Bikes is to provide a fitting data set that is so accurate that I can build a bicycle to a drawing, ship the bike halfway around the world to a client I have met once and have confidence that the bike will fit perfectly with only a couple of millimeters of possible saddle height adjustment because of the density of the foam in the saddle!

I had been riding “stock” frame geometry for decades and the possibilities created by the combination of an unlimited fitting system and true custom geometry did not exist for me, and thus for you, until fairly recently. The time honored principles of Knee Over Pedal Spindle, (KOPS), the Lemond method, standover height, saddle height equal to hip height when standing next to the bike and scads of other techniques were developed to help people choose a bike size that would work for them.

We need to look at a bit of history because bikes were made quite differently in the 1970’s and before than they are today. The ‘70’s were a time where road bikes had a much different geometry, with seat angles in the 71-72 degree range. Additionally these bikes were built in half sizes and thus had as many as 12 sizes for one model! Today’s bikes have between 3 and 5 sizes so more people are forced to “fit” a bike that will be less than perfect.

The archetypical road bike in the 70’s was the Raleigh Team Professional, which was arguably one of the best and most comfortable racing bikes ever made. At this time there were two schools of racing as well, a European style which was centered on longer rides and races including mountains. An American style developed as well focusing on Criterium racing; shorter closed course races with lots of turns and sprints. The American bicycle manufacturers started producing bikes with 73-74 degree seat angles and much less saddle setback with the logic that our races were shorter and one didn’t need the comfort for a 125 mile race if we were racing for 50 miles.

This style of racing bike geometry became popular as Americans liked the more aggressive position and the young racers working in bike shops could sell these bikes. We now are in a time when most nice bikes are still designed for young professional racers, but are purchased by successful people over 40. I have seen my position change on the bike since I was able to use my setup bike to experiment. I found that the bars really needed to be higher and the saddle needed to be further aft to get the balance points right.

I also found that as I got older (and had some injuries on the way) that my tolerance for the more aggressive geometry was no longer possible. People who came into my studio tended to be folks who had no success getting fitted in other bicycle stores so I had more challenging cases on a day to day basis. I saw more and more people who could not get comfortable on their stock bikes and even had to abandon the respected WobbleNaught fitting system because it tied the individual to an existing bike.

The setup bike began to show me that when one truly was in balance that many good things started happening. First, saddle problems diminished and disappeared completely for most people. Second, low back pain went away. Third, hand numbness was diminished. Additionally people’s ability to ride greater distances improved and incredibly, their power and efficiency improved so they were faster. There was only one problem. The positions that I discovered turned out to be very close to the riding position people had on the old Raleigh Team Pro! It seems that what is old is new again.

It is a long uphill battle to convince production frame manufacturers to build bikes that “grown ups” can ride, but fortunately a handful of expert custom frame manufacturers exists now. I have great success in designing a custom frame based on real individual setup data and can work with these experts to create a frame that has predictable ride characteristics and will be the servant of the rider, not the other way around.
I still get a few people who are the right size for a stock frame but have found that at this level, almost everyone seems to want a well designed custom bike. People seem astonished when they learn that bike riding can be comfortable and much more enjoyable than before. The process is simple; get balanced on the bike first and put the handlebars in the right place second. The geometry of the bike can be a help or a hindrance to a rider and thankfully there are solutions that will allow anyone to be comfortable on a bike.

About the Author

KGS Bikes is known as the world's premiere bicycle fitting studio and boutique. Kevin Saunders, President, has over 25 years experience in high-end bicycles and bicycle fitting. KGS Bikes sells bicycles from Co-Motion Parlee, Serotta, Zinn, and Guru, in addition to fitting services. For more information visit the KGS Bikes website, http://kgsbikes.com and our KGS Bikes blog,http://blog.kgsbikes.com.

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