Hi Kevin! (thanks for your kind words elsewhere)
Ah, this is one of those evergreen topics that is a real favorite of mine, so thanks for bringing it up!
As a hobbyist framebuilder with an interest in the science behind bicycles, I investigated this myself some years ago and built nearly identical forks of each type and then instrumented them. As it happened, so did professinal framebuilder Dave Kirk (
http://www.kirkframeworks.com/ ), who reported his results over at
Road Bike Review. His methodology and results mirror mine:
http://forums.roadbikereview.com/276129-post20.htmlHere's how the differences between the two kinds of forks lay out...
= Straight bladed forks and raked ones (with curved blades) can result in identical geometry (trail, effective head tube angle) in the same bike. How/why? Well, the straight blades are also raked...but the rake occurs at the crown (the sockets are set at an angle). So long as the dropouts end up in the same place, it matters not what happens in-between; the
geometry of the bike will be the same.
= Because curved blades are longer, they do tend to exhibit more deflection over their greater length than stiffer, shorter straight blades under load when hitting bumps. Because of this,
curved blades tend to be more comfortable. The margin is pretty slim, however, and all variables have to be held constant if one is to have any hope of a direct comparison. Because straight blades are shorter, they do also tend to terminate at a different section of the available blade length, and this affects feel as well because of a difference in cross-section.
= It costs considerably less to make a fork with straight blades because one entire step is left out. Curved-blade forks often start as straight forks, then are raked as a unit. Other builders rake the blades individually (or buy them pre-raked for convenience, then alter head tube angle to get the desired geometry or bend the blades further as needed), then build, but I preferred to rake my own forks as a unit to get the geometry I wanted. Blades are almost always raked "cold", though I have known some builders who used heat in the process (no! Heat -- and more of it -- can adversely affect the integrity of the steel, so builders take pains to keep temperatures as low as possible to avoid overheating the steel).
= Apropos nothing in particular, but it is useful to remember that raked blades have been bent beyond their elastic deformation into the plastic zone (cold-set). Some people argue that straight blades don't undergo these stresses, and so are naturally "springier". I would argue that once a blade has been cold-worked and normalized, any changes in the quality of steel are moot, and are affected to a much greater extent by (over)application of heat thereafter (in the building process).
= One oft-overlooked advantage of curved blades for touring forks is the greater ease with which front racks can be fitted, and better weight distribution as a result. Try putting a Tubus Tara or Duo on a straight-blade fork, and it will project considerably further forward than when mounted on a curved-blade fork (see attached pic for an example). Why? The lower attachment point of the rack often ends up *ahead* of the axle instead of behind it, thanks to the straight-blade's path. As a result, more weight is carried forward on the front wheel and handling suffers to a degree.
To sum up, a curved-blade fork will be a bit more comfortable than one with the same geometry that has straight blades because the curved blades are a little longer. The difference won't be much, but it is most likely to be felt when hitting bumps while riding -- when people will notice it most. Straight blades are cheaper to produce, and curved blades make it easier to place front panniers where their weight is more properly carried.
Regardless of how the blades are raked (or not), a greater determinant of comfort is likely to be tube-wall thickness. Remember, the C2 fork is made from lighter, competition-gauge tubing that is very thin, and cannot be fitted with lowrider bosses for carrying luggage. That light-gauge tubing is also longer than a straight-bladed fork, thanks to the greater length needed to curve the blades. No wonder it feels so nice and compliant! Fit this fork with a wide-cushy tire, and the result is real comfort.
All the best,
Dan.
