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From the mag: Bottom bracket designs evolve to quiet the creak

Published April 26, 2013
From the April 15 issue of BRAIN

APTOS, CA (BRAIN) — There may be a sliver of light at the end of the tunnel for retailers frustrated with creaky, plastic-y, non-serviceable OEM bottom brackets in $8,000 bikes.

A new generation of aftermarket designs goes directly after creak and serviceability issues. Cartridge designs from Praxis Works and Real World Cycling are made of aluminum and thread together inside press-fit shells. 

Most of this first wave of designs target adapting Shimano cranks into BB30-sized frame shells—so-called converter or conversion bottom brackets—since this style is in high demand. But expect the same tricks to trickle down to other sizes and bottom bracket applications.

“Using separate left and right cups means they can articulate independently; they can creak and walk right out of the frame,” said Adam Haverstock, Praxis Works’ director of marketing and sales.

“By going to a cartridge-style design, our bearings index off each other and are not as impacted by damaged or out-of-tolerance shells,” he said. 

The $85 Praxis Conversion BB is designed to adapt Shimano cranks to BB30 or with a shim to PF30 frames. It offers a similarly designed version for Specialized OSBB bottom bracket shells. 

The non-drive part of Praxis’ aluminum cartridge is press fit into any BB30 frame with a headset press. The drive side of the cartridge is threaded into the non-drive side using standard Shimano external bottom bracket tools.

As the drive side cup is threaded in, it expands a collet pressing against the drive-side bearing seat in the shell. This “locks” the cartridge to the shell, which should eliminate creak and keep the cups from moving within the shell. 

The cartridge has a slight hourglass shape to provide clearance within the shell to eliminate any potential for noise there.

Praxis includes a Delrin shim with its BB30 cartridge for use with the larger PF30. Similar to installation into a BB30 shell, the non-drive side of the cartridge and shim are pressed into the shell, and the drive side is threaded in. As the collet expands it presses the Delrin into the shell.

Real World Cycling (RWC) converters are based on KCNC aluminum cartridges and use Enduro bearings. They range in price from $55 to $130 depending on bearing choice—standard, angular contact or ceramic. The cartridges adapt Shimano cranks, as well as most GXP cranks, to BB30 frames. RWC offers a different cartridge to adapt Shimano cranks to the larger PF30 shell.

In addition to the cartridge approach, these RWC bottom brackets minimize metal-on-metal contact, and out-of-spec shells, by using O-rings to isolate the cartridge from the bottom bracket shell.

“You cannot face or ream a carbon frame, so you have to be able to deal with things being slightly out of spec. There is just enough give in the O-rings that you should be able to push the cups in with your hand or lightly with a press,” said Chris Streeter, Real World Cycling’s owner.

“In metal shells, minimizing metal-on-metal contact with the O-rings should help eliminate creak as well,” he added.

Once the cups are pushed in, they are threaded together with standard Shimano bottom bracket tools until the cups meet in the center and contact is made between the flanges and the shell.

Wheels Manufacturing recently released an aluminum cup PF30 bottom bracket that is not an adapter design—it works with BB30 cranks. It’s available with traditional bearings for $49, and angular contact bearing and ceramic bearing options are priced accordingly.

Like the RWC cartridges, it uses O-rings to minimize metal-on-metal contact. But its two bearing cups press together like OEM systems; they are not threaded together like in the cartridge designs. Since the cups are alloy the bearings can be replaced.

In addition to stopping creak and bearing creep, shops also have to be able to fit single or double cranks to mountain bikes or triples to road bikes with non-threaded shells.

Wheels Manufacturing’s $200 BB30/PF30 65-piece Universal Adapter kit help shops deal with non-standard requests. It provides enough adapters to fit four Shimano cranks, and four SRAM cranks to most styles of non-threaded bottom brackets, including mountain bikes, 2x10 systems, narrow-shell road bikes, road triples and other combinations.

“It’s not only getting Shimano cranks into BB30 frames; shops are dealing with single, double and triple road and mountain bike systems. This kit not only provides the right adapters for cranks, it also offers wave-washers so shops can adjust chainline,” said Dan DePaemelaere, Wheels Manufacturing sales manager.

 

Topics associated with this article: From the Magazine

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