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Converting a BB92/24mm press fit to BB30

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Converting a BB92/24mm press fit to BB30

Old 07-09-17, 09:13 PM
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oleosanxez
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Converting a BB92/24mm press fit to BB30/PF30

I have a 2011 Trek HiFi Deluxe that fits me like a glove but whose weight leaves much to be desired. Other than a new wheelset and headset, I'm trying to figure out the best (whatever price) upgrade for the BB and crankset that may be out there.

After a lot of googling it seems like the Chris King press fit (PF) 24mm ceramic BB is the way to go....if I want a shimano, truvativ, or some older race-face (RF) or FSA crankset, for which there aren't many cherry, top-o-the-line models left to choose from.

There are a couple of SRAM-, race-face-, and FSA-specific "mutated" BB92/24mm spindle options but that often means purchasing its brand of crankset.

Thus, it seems like if I want to have some actual choices for a modern, double (possibly single, though not preferred), carbon/lightweight alloy, Jedi-level crankset (I currently have the stock RF triple it came with) it's looking more and more like the best thing to do is convert the BB92 to a PF30. If that's even possible, which I obviously don't know.

Measured, the HiFi has a 95.5mm shell width and I'm not sure of the length of the spindle (but could measure it with American standard tape and convert to metric if it helps). It also has a 7mm ream depth and a 41.00 bore diameter ( mm).

What's disconcerting though is the PF30, according to Chris King (CK)'s site, has a 46.00 (+0.00/-0.05) bore diameter ( mm) and I wonder if a 30mm spindle will even fit, and if it does, do the bearings become too small to even last a season before wearing out, especially ceramic bearings?

Obviously, chain line (and possibly a new front der, which I'm going to upgrade anyway) may become an issue. And I believe CK has a BB92 to PF30 conversion kit--if I'm understanding their charts correctly (it's Sunday so I'm calling their tech support tomorrow when they open to dig some more).

But I wanted to see if anyone here may have experience in doing this and any advice or resources they could offer, other than "don't do it" or "buy a new frame". Those may very well be good pieces of advice but the frame has sentimental value to me and (I think) this is a doable procedure. Thanks a lot for reading and for any info.

Last edited by oleosanxez; 07-09-17 at 09:14 PM. Reason: Nomenclature correction
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Old 07-09-17, 11:54 PM
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cpach
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Just get a 24mm spindle crankset. There are plenty of high end cranksets with 24mm spindles. It is just barely possible to squeeze a 30mm spindle and some bearings in a BB92 shell, but it requires really small bearings, and requires a long spindle, like on a BB386 crankset (FSA), a Rotor crankset, or a Praxis crankset. You can definitely not use a BB30/PF30 proper crankset, as the spindles are too short.
Also ceramic bearings are hella expensive and offer minimal performance advantages--unless absolutely everything else is top of the line, I'd consider this a waste of money.

If you're obsessed with spindle width and want a more boutique crankset, I'd probably recommend getting a Praxis BB. They make BB92 bearings for either 30mm Rotor/carbon Praxis cranks, or their own BB standard for their alloy cranks. They manage slightly saner bearing sizes by making the bearing surface that is pressed in also the outer bearing race.

But seriously the larger spindle will save you like 60g. Do you have a <200g saddle? Carbon rims <400g? Carbon handlebars? Ultralight hubs for less than <350g a set? Ultralight pedals made out of ti and such? These would all be more effective ways to drop weight.
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Old 07-10-17, 01:45 AM
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trailflow1
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Originally Posted by oleosanxez View Post
What's disconcerting though is the PF30, according to Chris King (CK)'s site, has a 46.00 (+0.00/-0.05) bore diameter ( mm) and I wonder if a 30mm spindle will even fit, and if it does, do the bearings become too small to even last a season before wearing out, especially ceramic bearings?
That CK wont fit, how can a 46mm fit into a 41mm bore shell ?

BB92 (41mm) can be converted to BB30 (only longer spindle cranks) but you are limited to certain models of adapters and cranks. Also it's probably best to match both to the same brand to ensure proper compatibilty.

adapters -


Rotor Pressfit 4130 BB
PRESS FIT 4130 - BB89 / BB92 - Bottom Brackets - Triathlon - PRODUCTS

e*thirteen BB92 Bottom Bracket
Race Face BB92 30mm Bottom Bracket > Components > Drivetrain > Press Fit | Jenson USA

Race Face BB92 Cinch BB
Wiggle | Race Face BB92 'Cinch' 30mm Bottom Bracket | Bottom Brackets

BB92 to BB30 BB
BB92 TO BB30 BOTTOM BRACKET KIT

Praxis M30 BB (only to be used with Praxis M30 based cranks)
https://praxiscycles.com/product/m30-bb86-road/



Cranks -

Rotor Rex1 MTB crank
Rotor Rex2 MTB crank

e*thirteen LG1 crank
e*thirteen TRS+ crank
e*thirteen XCX crank

Race Face Next SL Cinch crank
Race Face Sixc Cinch crank
Race Face Turbine Cinch crank

Praxis CADET M30 crank
Praxis LYFT M30 crank
Praxis LYFT HD M30 crank
Praxis GIRDER M30 crank

Last edited by trailflow1; 07-10-17 at 02:07 AM.
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Old 07-10-17, 11:55 AM
  #4  
oleosanxez
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Originally Posted by trailflow1 View Post
That CK wont fit, how can a 46mm fit into a 41mm bore shell ?

BB92 (41mm) can be converted to BB30 (only longer spindle cranks) but you are limited to certain models of adapters and cranks. Also it's probably best to match both to the same brand to ensure proper compatibilty.

adapters -


Rotor Pressfit 4130 BB
PRESS FIT 4130 - BB89 / BB92 - Bottom Brackets - Triathlon - PRODUCTS

e*thirteen BB92 Bottom Bracket
Race Face BB92 30mm Bottom Bracket > Components > Drivetrain > Press Fit | Jenson USA

Race Face BB92 Cinch BB
Wiggle | Race Face BB92 'Cinch' 30mm Bottom Bracket | Bottom Brackets

BB92 to BB30 BB
BB92 TO BB30 BOTTOM BRACKET KIT

Praxis M30 BB (only to be used with Praxis M30 based cranks)
praxiscycles.com/product/m30-bb86-road/



Cranks -

Rotor Rex1 MTB crank
Rotor Rex2 MTB crank

e*thirteen LG1 crank
e*thirteen TRS+ crank
e*thirteen XCX crank

Race Face Next SL Cinch crank
Race Face Sixc Cinch crank
Race Face Turbine Cinch crank

Praxis CADET M30 crank
Praxis LYFT M30 crank
Praxis LYFT HD M30 crank
Praxis GIRDER M30 crank
Thanks a lot! You've provided some great resources. Rotor seems to have some especially great options and a handsome design as well. Again, many thanks!
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Old 07-10-17, 12:03 PM
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Originally Posted by cpach View Post
Just get a 24mm spindle crankset. There are plenty of high end cranksets with 24mm spindles. It is just barely possible to squeeze a 30mm spindle and some bearings in a BB92 shell, but it requires really small bearings, and requires a long spindle, like on a BB386 crankset (FSA), a Rotor crankset, or a Praxis crankset. You can definitely not use a BB30/PF30 proper crankset, as the spindles are too short.
Also ceramic bearings are hella expensive and offer minimal performance advantages--unless absolutely everything else is top of the line, I'd consider this a waste of money.

If you're obsessed with spindle width and want a more boutique crankset, I'd probably recommend getting a Praxis BB. They make BB92 bearings for either 30mm Rotor/carbon Praxis cranks, or their own BB standard for their alloy cranks. They manage slightly saner bearing sizes by making the bearing surface that is pressed in also the outer bearing race.

But seriously the larger spindle will save you like 60g. Do you have a <200g saddle? Carbon rims <400g? Carbon handlebars? Ultralight hubs for less than <350g a set? Ultralight pedals made out of ti and such? These would all be more effective ways to drop weight.
Fair questions and the answer is indeed a yes. I have carbon rims and a CK wheelset, headset, carbon handlebar, shifter pods, et al. The frame is aluminum and can achieve a somewhat light weight without the rest of the stock grouppo weighing it down, thus the desire to max out the weight savings elsewhere. I'll def check out Praxis as I'd rather not have to convert to PF30 and keep the engineers original intent of the frame to have a 24m spindle. Thanks a lot.
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Old 07-10-17, 11:49 PM
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I think I may have found what I'm lookingfor

Going to go with the Rotor Press Fit ceramic 4130 BB and the Race Face Next SL carbon/titanium spindle crankset (445g!), assuming they're compatible. If not, Rotor makes a slick looking crankset, the 3D+ CNC/aluminum which comes in at a whopping 497g (<175mm). Pretty decent.

Looked for something in this weight range for the 24mm spindle but either google can't find it (using every search term, quoted and unquoted, I could conceive of) or they just don't exist. (Thinking it's the latter.) Ebay, amazon, jenson, backcountry and several others turned up empty. Would like to have checked QBP but don't have a membership.

Each of these cranksets can be made a double or single too which is perfect. Thanks again for the tips and info.
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Old 07-11-17, 12:27 AM
  #7  
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4130 and Next SL combo will work. Knock yourself out--enjoy the bike.
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