Which Bottom Bracket for a custom frame?
I'm lucky enough to be on the waiting list for a custom titanium frame. I've been wanting a custom ti frame since i've been 14 years old and I'm finally making the leap (only took me 20 years). I've got most of the major details worked out but i'm seriously fretting over which bottom bracket standard to go with. I'm not beholden to a specific brand, shimano or sram, but I lean towards shimano cranks and sram shifting. I have a nice Chris King english threaded bottom bracket that I was planning on using but I've been tempted with all the new bottom bracket designs. I'm not sure if I'd be able to tell the difference while I was riding but I do like the idea of having a bottom bracket that helps make the frame more "future proof" and easier to work on. I do all my own repairs and i have found the traditional threaded BB super easy to work on and adjust.
What would you guys do? What did you do?
"You can become a very fast donkey, but you'll never be a thoroughbred..."
Which Bottom Bracket for a custom frame?
I would get a standard bottom bracket and use the King.
I like the external bearing BB (BSA, English Thread), both Shimano and SRAM support that style. I'd rather not deal with any of the press fit kinds. Two of my bikes have the external bearing BB, one uses Shimano Hollowtech cranks, the other is a GXP BB with XX1 cranks. Simple to install and service.
Take your frame makerís advice for starters. If he is more comfortable building one type over another you should stick with what he does best. If he doesnít have a strong opinion, I would err on the side of conservative, and go with threaded. Theyíre easily replaceable, or in the case of the King, rebuildable, less prone to creaking, easy to find at any LBS in a pinch, donít cause any frame wear if installed or removed properly, and can work with most cranksets commonly available. Since a Ti bike is considered by most to be a splurge, or lifetime purchase, you want it to last as such, so you need to be aware of some of the pitfalls of the press-fit systems; The BB shells are thin, so welding (heat distortion) and machining (size, alignment, and concentricity) are all a critical one-chance proposition, pressing bearings in and out causes wear, or possibly ovalization of the bore if things go wrong. If any one of those items is not correct, you are very likely to have creaks or other annoying problems. Threaded systems in contrast, are simple and rock-solid in most every way. If you DO manage to bugger the threads by mistake, they can be repaired (chased) by any LBS. Additionally, a bottom bracket needs to be a serviceable item, so a press-fit assembly is not very convenient, and if you think about it, doesnít make much sense. Headsets Ė OK. Iíve never had to remove or replace one. Bottom brackets, Iíve had to replace after one wet, muddy race. The problems with press-fit systems are probably all rare occurrences, but with a lifetime frame, why take the risk?
Thatís what I would do, and thatís what I did. Good luck!!
Threaded for sure. My reasons:
- There is no press fit standard. PF30/BB30 is a SRAM thing and requires some less than ideal adaptation to fit a Shimano. BB92 is mostly a Shimano thing and doesn't work with GXP in my opinion (a press fit bearing system requires pre-load, which GXP doesn't offer).
- Maintenance as well detailed above.
- My personal experience with PF30 bearing life was pretty poor and others have had similar issues (though some others have had great luck).
The biggest benefit of press fit BB's in my opinion is the options it gives for manufacturing. The PF/BB30 shell diameter is much larger which allows the use of large, hydroformed downtubes. This probably doesn't apply in your case. The benefit of BB92 is that it gives a much wider shell which makes it easier to bring the chainstays in if you're shooting for a short stays. This may or may not be a benefit to your fabricator.
Another vote for threaded. I have gone through four different bottom brackets in a year or so. Every time I was threading in whatever new cup I was installing at the time, I thought to myself.......man I'm glad I don't have interference fit bearings. In my mind, the thought of installing and removing "press fit anything" more than a couple of times would just lead to diminishing tolerances, creaks, and possibly damage.
Great question though, OP. I wish frame manufacturers would ask the same one.
Without doubt I would go for a threaded bottom bracket, for precisely the reasons that car_nut listed. The interference-fit "standards" are in their infancy, so who truly knows what will stick around and what will go the way of the dodo.
English (BSA) threaded bottom bracket shells are backwards compatible with 100 year old technology, and I predict they will continue to be around for the life of your frame.
Besides, you already have a King bottom bracket; this all just comes together beautifully!
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