Praxis Works Conversion Bottom Bracket – PART 2

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Speaking with the same mechanics as mentioned in PART 1, all had mentioned that the #1 problem with standard Press-Fit Bottom Brackets is that they tend to move & wiggle, creak & squeak, click & clack as well as make several other noises. Most had also mentioned that they had seen a few bottom bracket cups ‘walk out’ of a frame. Every mechanic had the same solution – use Loctite® thread locker on both the inside and outside of the plastic cups. Loctite® tends to keep the cups securely in place as well as keep the bearings locked into the cups.

Most frames today are built with press-fit shells. Why? Because it’s two less manufacturing steps not having to thread the left inside and right inside of the Bottom bracket shell. Ease of manufacturing and ease of assembly.

But, two BIG issues then arise for the cyclist. (1) As mentioned above, the cups will want to “walk around” when pedaling and (2) The bearings are inboard of the shell making for a less rigid bottom bracket. So, thinking out of the box, Praxis designs a press-fit bottom bracket that locks the cups together by threading one in to the other. BRILLIANT!!!

One can think of the Praxis conversion bottom bracket as a modification of the older external threaded bottom brackets where the cartridge bearings were located outboard of the frame, but, still using a modern press-fit design so it can be used on modern bicycles. This allows for much greater rigidity. Again, BRILLIANT!!! The Praxis Conversion Bottom Bracket takes this tried and proven approach and brings it to the next level.

Again, separating out the bearing issue from the Praxis cup/collet design, from an engineers point of view, I think that Praxis’ collet design is one of the slickest, simplest, and neatest solutions to keep bottom bracket cups from ‘walking around’. Praxis uses an expanding collet that, when tightened, sucks together and locks each cup into a single unit eliminating any movement of the cups in the BB shell. An added benefit to this design is that the bearings stay perfectly parallel to each other.

The cups for this conversion bottom bracket are sized externally to insert into a BB30 shell and internally to accept a bearing that accepts a 24mm crank spindle. Three solutions exist, one for Shimano, one for SRAM GXP and one for Campy Ultra Torque.

One thing that can be said for Praxis product support is that they have plenty of “how-to” instruction manuals on their website. For BB installation, every step is detailed to ensure that you will do it right. Before installing the BB, I read through their Conversion Kit Instructions PDF. Page 1 lists the prep work required along with a listing of what each piece is and where it goes. Page 2 describes the different installations (ex. Shimano, SRAM, Campy, Specialized) since each requires slightly different configurations. These are all thoroughly detailed, including pictures. By following their easy-to-follow instructions, you cannot make a mistake.
The entire BB30 conversion installation took me less than 10 minutes and that included a 5-minute coffee break!

After six months and thousands of miles, I finally had to give the bike back. The Praxis Conversion Bottom Bracket  exceeded my expectations. The collet locked the cups together and there was no movement whatsoever. No clicking or clacking noises. Only ultra-smooth operation.

Uninstalling the conversion BB was as simple as removing the crank arms, crank and unscrewing the drive-side external cup from the non-drive side collet.

The Praxis BB30 conversion bottom bracket with TPS ceramic bearings and plastic shims weighed in at 138 grams. An equivalent conventional BB30 conversion press-fit bottom bracket weighs in at 100 grams. 38 grams is 1.34 ounces so there is really no weight penalty compared to the rigidity that you get in return!

the all-steel bearing version of the conversion bottom bracket has an MSRP of $85. The hybrid-ceramic version is considerably more at $195. So, this is what I would do. Purchase the all-steel bearing version and run the bottom bracket for as long as their steel bearings hold up. Then, pop-out the steel bearings and replace with a set of 6805 SKF steel bearings or TPS 6805 ceramic bearings. What’s nice about the Praxis design is that you can leave the cups in the frame and remove and replace just the bearings. You will need to use a tool such as the Park Tool BBT-90.3 – PressFit Bottom Bracket Bearing Tool Set.

Bottom Line: If you need a conversion Bottom Bracket, this is the one to get! Going this route, you will have a quality and very well designed bottom bracket cup/collet solution that you can easily replace the bearings when they wear out. The recommendation above should last you for many years. Just a reminder, on the downside, if you touch or modify their bottom bracket in any way, you will void the warranty. But, on the upside, there’s really not much that can go wrong with the cup/collet so I say go ahead and replace the bearings when the original set wears out.

Every product I have seen from Praxis has been high-quality. This includes their Cranks, Chainrings, Cassettes, and both standard and conversion bottom bracket solutions.

• For Shimano Hollowtech cranks, specifically designed to precisely match Shimano’s bearing stance and chain line spec.
• Forged & machined heat treated 7075 T6 Aluminum
• Enduro 2437 ‘steel’ cartridge bearings with steel balls
• Enduro 2437 angular contact ‘ceramic’ cartridge bearings with grade 5 ceramic balls
• For 68mm BB30 ROAD, 73mm MTN, PF30, and Specialized OSBB Road frames
• NOT for BBRight, BB386EVO, BB86, BB92 frames
• NOT for FSA, Rotor, SRAM/GXP or CAMPY cranks at this time.
• For Shimano Hollowtech cranks, specifically designed to precisely match Shimano’s bearing stance and chain line spec.
• Compression/Spacer O-Ring compensates for frame width discrepancies
• Patent Pending Design