To many riders and mechanics, the last thing the cycling industry needs is yet another bottom bracket standard. But Chris King hopes that its new threaded T47 bottom bracket design could silence skeptics and, more importantly, bikes.
Chris King partnered with custom frame company Argonaut Cycles to develop what it hopes will be a new bottom bracket standard to replace the widely used — and often creaky — Press-Fit 30 standard. T47 bottom brackets use the same 46mm internal diameter as Press-Fit 30, but they thread into frames rather than being pressed in.
The development of a new bottom bracket
Argonaut will begin building its frames around the T47 standard
Ben Farver, owner of Argonaut Cycles, appreciates the increased surface area that the Press-Fit 30 bottom bracket shell gives over traditional BSA-threaded bottom bracket, but the interface is often sloppy and, thus, often creaky. The smaller diameter BSA treaded bottom bracket, on the other hand, severely limits crank options.
“As a frame manufacturer, I don’t want to have to talk someone into buying one of my bikes while at the same time talking them out of a crank they might want to use, Farver said. “My production manager and I were talking about all the challenges of PF30 one day and thought, why don’t we just make a new standard that solves both problems?”
“I called Jay Sycip, who runs the Cielo arm of Chris King, and we discussed the true consumer benefit of creating a threaded spec that leverages the larger bearing used in the PF30,’ he said. “We agreed that it would yield a much higher interface success rate, and more importantly, a better ride. So, this project is an attempt to solve a problem the entire bike industry is suffering from, and lead the way to a better, lasting standard.”
In theory, press-fit systems can work just fine, so long as everything is built within the proper tolerances. Lack of adherence to specified tolerances too often leads to creaky press-fit interfaces.
“The issue lies within the tolerance creep between frame manufacturers and component companies,” said Bob Scales, marketing manager for Chris King.
Oversized and threaded
The t47 bottom bracket standard uses the same diameter shell as press-fit 30 in a threaded (and hopefully quieter) package
This new platform is still in development and goes by several names. The actual standard is being called T47, while King is calling their T47 bottom bracket Thread Fit 30i. T47 will be an open standard, available to all manufacturers.
As stated earlier, the T47 system uses a bottom bracket shell with an internal diameter of 46mm — the same as Press-Fit 30. The difference being that the bottom bracket threads into the shell, rather than being pressed into place. The fact that the diameter of the shell is nominally the same as a Press-Fit 30 shell means it requires very little change to frame design in order to incorporate a large diameter threaded bottom bracket shell.
“The threaded system removes the performance risks associated with the convenience of the press-fit products and ultimately delivers a more reliable, high-performance product to the rider,” said Scales.
Like, Press-Fit 30, Chris King’s Thread Fit 30i bottom bracket is designed to accommodate cranks with 30mm diameter spindles — the most common size on today’s road and mountain bikes. King will also offer adapters so riders can also run cranks with 24mm diameter spindles.
Pricing and availability of King’s new bottom bracket has yet to be announced. More importantly, acceptance of this new bottom bracket interface by manufacturers is still an open question. Will it be adopted by the industry at large, or will it remain a niche concept?
We’ll bring you more information on the T47 bottom bracket platform as it develops, so stay tuned.