Originally Posted by Andrew R Stewart

We all like somewhat different frame design/bike handling manors. I have moved away from trail amounts of less then 60mm for the most part. If this were my bike I'd reduce the head angle to 72*. I'd also consider extending the stays a tad. Do you know how much seat set back you run? Do you know what your front center will be? What size tires will you typically use?


I see nothing wrong with your tentative design. But there's so much that one can take into account when designing a frame and I'd want a lot more info before I would feel that I had a handle on the givens, from which the resultants come from.


A few odd comments:


I think that the fork's contribution to the overall frame flex is greater then many talk about. I have felt a major increase in preserved frame stiffness between very similar self made steel bikes where one had a 1" steerer and the other a 1.125" steerer.


I think that "working" the TT has more impact on rear triangle stiffness then that of "working" the seat stays. One structural aspect that often get's left out of discussions is that most bikes rear ends are a three dimensional form made up of triangles, the rear axle is one of the edges and ties the two large side facets together. That results in a pretty stiff structure for the amount of material. OTOH the top tube is a simple beam with far less cross sectional area then any facet of the rear end. Stiffening up that helps to better tie the front and rear together, especially when seated or with a rear load IMO.


Bikes that "feel fast" can be so. But don't confuse human perception with actual measurement. The best example of this, and currently the new "thing", are tires. It's becoming more and more accepted that the narrowest tires are rarely the most efficient for a few reasons. Yet it's the wider tires' damping of the data transmission (from the road to the skin) that also seems to tone down the perceptions of what's going on, we think wider tires are slower. Some of us have been saying much the same but WRT frame geometry. The "sharpest/fastest/quickest" can often, for us mortals (and that's the rub, we dream we're gods), be slower and possibly less able then what we would have made.


Last thing I'll mention is that this is much of what I've gone through recently. I want to make a couple of frames for the wife and I which will be our weekend warrior rides. I made a couple of S&S coupled bikes for us a few years ago that, geometry wise, have been about perfect. So I have a wish to mimic their fit and handling traits and lighten them up. To best do so means a fork on her bike that no one makes as a stock production model. Now this isn't a problem if I were wanting (and this is all about wants) a steel fork. But I was really hoping for carbon. Weight is a major part of a pound less and the road feel can be pretty good, lastly not having to make and paint a "mini frame" twice is a plus. After going through many designs (I use BikeCad) I've come back to the need for a fit and a ride being more important then weight or effort. So a couple of days ago I ordered fork materials and will set the carbon forks aside. I guess I should see this as meaning that my painter has more canvas to work on... Andy