Bicycle Frame Geometry 101

I was discussing frame geometry with a prominentbikes. We now are in a time when most nice bikes are
coach last week and his perspective on framestill designed for young professional racers, but are
geometry struck a nerve with me so I wanted topurchased by successful people over 40. I have seen
share this topic with you. The nature of my business atmy position change on the bike since I was able to use
KGS Bikes is to provide a fitting data set that is somy setup bike to experiment. I found that the bars
accurate that I can build a bicycle to a drawing, shipreally needed to be higher and the saddle needed to
the bike halfway around the world to a client I havebe further aft to get the balance points right.
met once and have confidence that the bike will fitI also found that as I got older (and had some injuries
perfectly with only a couple of millimeters of possibleon the way) that my tolerance for the more
saddle height adjustment because of the density ofaggressive geometry was no longer possible. People
the foam in the saddle!who came into my studio tended to be folks who had
I had been riding “stock” frame geometry forno success getting fitted in other bicycle stores so I
decades and the possibilities created by thehad more challenging cases on a day to day basis. I
combination of an unlimited fitting system and truesaw more and more people who could not get
custom geometry did not exist for me, and thus forcomfortable on their stock bikes and even had to
you, until fairly recently. The time honored principles ofabandon the respected WobbleNaught fitting system
Knee Over Pedal Spindle, (KOPS), the Lemondbecause it tied the individual to an existing bike.
method, standover height, saddle height equal to hipThe setup bike began to show me that when one truly
height when standing next to the bike and scads ofwas in balance that many good things started
other techniques were developed to help peoplehappening. First, saddle problems diminished and
choose a bike size that would work for them.disappeared completely for most people. Second, low
We need to look at a bit of history because bikesback pain went away. Third, hand numbness was
were made quite differently in the 1970’s anddiminished. Additionally people’s ability to ride
before than they are today. The ‘70’s were agreater distances improved and incredibly, their power
time where road bikes had a much different geometry,and efficiency improved so they were faster. There
with seat angles in the 71-72 degree range. Additionallywas only one problem. The positions that I discovered
these bikes were built in half sizes and thus had asturned out to be very close to the riding position people
many as 12 sizes for one model! Today’s bikeshad on the old Raleigh Team Pro! It seems that what
have between 3 and 5 sizes so more people areis old is new again.
forced to “fit” a bike that will be less thanIt is a long uphill battle to convince production frame
perfect.manufacturers to build bikes that “grown ups”
The archetypical road bike in the 70’s was thecan ride, but fortunately a handful of expert custom
Raleigh Team Professional, which was arguably oneframe manufacturers exists now. I have great
of the best and most comfortable racing bikes eversuccess in designing a custom frame based on real
made. At this time there were two schools of racingindividual setup data and can work with these experts
as well, a European style which was centered onto create a frame that has predictable ride
longer rides and races including mountains. Ancharacteristics and will be the servant of the rider, not
American style developed as well focusing onthe other way around.
Criterium racing; shorter closed course races with lotsI still get a few people who are the right size for a
of turns and sprints. The American bicyclestock frame but have found that at this level, almost
manufacturers started producing bikes with 73-74everyone seems to want a well designed custom bike.
degree seat angles and much less saddle setbackPeople seem astonished when they learn that bike
with the logic that our races were shorter and oneriding can be comfortable and much more enjoyable
didn’t need the comfort for a 125 mile race if wethan before. The process is simple; get balanced on
were racing for 50 miles.the bike first and put the handlebars in the right place
This style of racing bike geometry became popular assecond. The geometry of the bike can be a help or a
Americans liked the more aggressive position and thehindrance to a rider and thankfully there are solutions
young racers working in bike shops could sell thesethat will allow anyone to be comfortable on a bike.