Frame Components:

Pacenti 22.2 O/S Bottom Bracket Shell

Designed by Kirk Pacenti and Tom Kellogg to offer builders the unique ability to create frames with stiffer chain stays, bottom brackets and rear triangles than oval chain stays offer while enabling improved tire clearance over traditional round chain stay shells. With the exception of the Kirk/Kellogg bottom bracket, 22.2mm Bottom Brackets have not been redesigned since the advent of modern chain lines. During the period when state of the art frames were designed for 5, 6, 7 & 8-speed drivetrains, component manufacturers' designs required very narrow chain lines which in turn required narrow-set chain stays. Those chain lines went away many years ago but there was no effort to alter shell designs until Kirk and I did so.

Our shell offers enough clearance for much larger tires than other shells using the same amount of relief. Even when building for Cyclo-X, sufficient tire clearance can be built into your frames. The only potential drawback is that you will need to dimple the right chain stay for certain cranksets to a more significant degree than you would have with older designs. We have found that most compact and triple cranksets require no dimpling and that only some traditional and all track cranksets require dimpling. Finally, we tweaked the included angles of the shell to make fitment easier with modern bottom bracket heights, front centers and chain stay lengths.

Spectrum 4130 Chain Stays

DISCUSSION:
Our Spectrum Chain Stays are different from all others on the market. They are lighter than all but the most flexible and stiffer than all but the heaviest. Because Chain Stays are stressed primarily in shear, (torsion) they are most structurally efficient when they are round. Ours are round. Because custom builders need the ability to tailor the degree of drivetrain stiffness characteristics for each client, we have designed our Chain Stays to give builders a wider range of torsional and lateral stiffness than possible with any other chain stays. Reynolds produced these stays to our specifications. We had them start with much longer blanks than they normally use so that we could offer a much longer straight (22.2mm) section. The butting process is also different than their normal one in that the Spectrum stays end up with a true taper gauge. i.e. the gauge at the small end is the same as it is at the big end.

We had considered ordering the stays in 531 material because of its excellent notch hardness properties, but the weldability of the material would have suffered and we wanted all builders to be able to use these amazing Chain Stays. In combination with the Spectrum/Pacenti bottom bracket, these stays offer the widest range of drivetrain and rear triangle stiffness available in custom steel frames. Please call Tom or Jeff if you have questions.

Spectrum 4130 Seat Binder

These CroMo steel binder bosses are machined for us by a company which makes very high precision items for the defense industry and NASA. In fact, these binders are much stronger and more accurately machined than is necessary, but we wanted them right, and Tim's company only does things right.

In order to slot these binders builders will need a Pure Carbide slitting saw which is in good shape. High Speed Steel saws will simply not hold up to these binders. At the same time, the threads simply can not strip out ... ever. They are that strong. We have used these binders for our seat lugs for years and also for custom handlebar stems, tandem front BB binders, etc.



"MER" Fork Crown

Spectrum 1.125" Steerer Conversion Plugs & Race Seats

Jeff and I developed these plugs about twenty years ago to enable us to convert traditional 1.0" crowns for 1.125" steerer tubes. The design allows us to put more strength and stiffness where we need it and less where we don't. Since the plug acts as a steerer butt, a 1.125"*.035 tube is used for the steerer, resulting in an exceptionally light and strong steel fork.

Shimano Chain Stay Stops ("outer stopper")

We cleaned Shimano out of these little babies many years ago after they got out of the frame component business. They function just like a traditional "Diving Bell" type stop, requiring a reduction ferule. They are NOT Italian stylish, but more in line with our aesthetic of clean functionality.