Saturday, June 11, 2011

My Randonneuring Bicycle, Part 5: Geometry

The first thing I discussed with my builder, Tony Pereira, was the geometry of my first custom made bicycle. Unfortunately, I didn't possess a broad perspective from owning a myriad of bicycles. My last new bicycle I bought in 1975. I only knew it had never felt quite right.

It was tall enough for my legs, but I felt too stretched out. My trips to my bike-fitting physical therapist confirmed that my old Fuji was too long. By combining an inappropriately short stem with an inappropriately forward saddle placement on the seatpost, I could get where I needed to be, but the bike was essentially too long for me.

That is to say, if I matched my top tube length to the norms in the industry given my seat tube length, then the top tube would be too long. Tony agreed after I took my Fuji to his shop. The result then was a truly custom geometry suited to my body.

I can see you now imagining this long-legged, short-torsoed guy typing this out on his keyboard, right? Well, I've concluded it is less about my actual body proportions and more about my inflexibility in my back. Some is due to a general inflexibility, but some might also be a result of my old bricklaying/marble masonry days. At any rate, geometry is crucial to my bike fit, and Tony got it right. I know this because it feels right, but my bike-fitting physical therapist confirms it too. Saddle sits where it ought. Stem is right. Over the pedals in way that is efficient.

So, here's where I get a little fuzzy. To accomplish this, Tony had to compress my top tube. Doing that while keeping my seat tube long enough means that the angles got steeper. This isn't ideal for a randonneuring or long-distance bicycle, but what to do? I think there is nothing else to do. Lower trail in the fork or longer chainstays matter some, but this is all a package. And for Tony, as a custom builder, he is always thinking about the whole. How does the bike fit together? Measurements, Angles, Tube Diameters, Wheel Size, Toe Overlap, Centering Over the Pedals, Handlebar Bag Placement Over the Front Geometry, Bottom Bracket Height, Crankarm Length, etc.

As I said, my perspective is limited, but this is how I view it today. I will post soon about the other features, quality of build, component choices, wheel size, etc. But geometry is fundamental even though all are integrated.

I am satisfied with the geometry, and if there were one thing here I'd change--and had unlimited resources--I'd be interested in another fork resulting in an even lower trail. I'd be intrigued to see how that affects the handling, and I'd learn from that broader perspective. Might be better, might be worse, but it would be good to see. If wishes were horses....

Keep it geometric,


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