It doesn't matter under most conditions, but at high speed in a crosswind my Capo, with its somewhat long fork rake and long wheelbase, feels considerably less twitchy than my Bianchi.

The Capo certainly is comfortable over bumps. :)

Taking things to the extreme... <68 degree frame angles, trail in the 4 inch range, a fork that was designed to function as a secondary shock absorber, an immense wheelbase, and oversized 28 inch wheels makes for one incredibly plush ride.

Add to that a rear ward riding position that un-weights the handlebars and you have a bike that has a ride quality that is, in my experience, without equal.

I have ridden a number of Raleigh Tourists and although they share the same geometry and parts I find that my '48 Rudge has an even nicer ride. That might have something to do with how the frames were built and the materials that were used.

http://www.ravingbikefiend.com/bikep...illebooth1.jpg

Hey, that's Dr. Who's bike!

I was thinking about the Tardis when I shot this...

OK, can someone explain to me about track bike geometry?

My understanding of trail and handling is that there is a tradeoff between high and low speeds:

Low trail=low speed stability (quick handling because you can make fast directional adjustments), less stability at high speed (because of quick reaction time)

Hi trail= low speed instability (wobbly handling at low speed), great high speed stability (rides like its on rails at speed)

So which do you want for a track bike? I always assumed that track bikes (which I've never ridden) would have high trail for stability at speed, speed being something you hopefully are spending a lot of time with on the track (which is consistent with very low fork rake that I've observed on track bikes)

However, maybe being nimble (low trail) is actually better for weaving in and out of your competitors. And somehow, despite the bike's being twitchy at speed, you don't lose control when you're hammering away.

Which is it?

That's the reason Reynolds made such a fuss about their "taper gauge" fork blades. A straight gauge tube when tapered (22mm a the crown end down to 12mm at the dropout end) will get thicker at the dropout end. Reynolds addressed this by putting a long, gradual butt in their fork blade -- thick at the crown end and thinner at the dropout end -- so when the blade was tapered the end result would be a more or less uniform wall thickness for the entire length of the blade. Here's an end-on view of the crown and dropout ends of a pair of Reynolds 531 fork blades as shipped from the factory:

http://os2.dhs.org/~john/taper-gauge.jpg

This was generally recognized as a Good Idea, and by the 80s most other tubing manufacturers had implemented similar practices with their fork blades.

The fork trail and rake have absolutely nothing to do with whether the fork is straight or curved. Straight forks are angled appropriately out from the fork crown, and so it makes no difference whatsoever.

John you should try my RIGI with a 37.5 wheelbas and 77.5 head and 78.25 seat tube angles I am not sure if the current fork provides the correct 1.5" rake but it is a bit 'squirrely' at times

This is absolutely true. The only thing the fork curve affects is shock absorption and aesthetics. Aesthetics are a personal matter and shock absorption is something that can be quantified either in a lab or via some modeling. The vector diagram presented previously demonstrates the concept of fork curve on shock absorption but doesn't quantify the effect.

On a track bike, you want lower trail for maneuverability. Stability at high speed isn't as much of an issue since you're generally not riding for hours at a time and the banking is doing the cornering for you. High trail bikes corner via lean and steer more from the hips; low trail bikes steer more from turning the bars and allow for quick change of direction. A bike for a 6-day race, like those ridden in the early 20th century, would regain some long-distance comfort via a slacker seat tube angle. A bike built for a longer track event will also gain some stability via a lower bottom bracket than a bike for a sprint event.