BB92 (Shimano bottom bracket) with SRAM 30mm crankshaft (X01 or XX1 BB30)?

Question

The frame that I want to build has BB92 bottom bracket hole.

The drivetrain I want to use is 1x11 SRAM XX1 or X01 with 30mm crankshaft (BB30)(edit: also available GXP).

There are ways to fit it - directly pressing these bearings (or similar from other manufacturers) into the frame so the 30mm shaft will fit.

The question is will it fit also length-wise (will length of shaft be compatible) or same spacers are necessary and is the solution a good one (prone to squeaking, no bad experience with such setup etc.)?

Edit: Other possibility is to use GXP X01 or XX1 crankset. Since those spindles are stepped it wont work with BB92 shimano bottom bracket, but will fit with GXP BB92 press-fit bearing cups (which is similar solution to the firts one)

Which solution is the better one?

Answer 1

BB92 is also known as PF41. The shell width should be 91.5mm and the inner diameter should be 41mm.

30mm:

According to SRAM's 1x11 frame fit specifications, the inner part of the XX1 "spider" sits 45.5mm from the centreline (Dimension W1). The equivalent dimension is 43.5mm for X1 cranksets.

MTB BBs compatible with Hollowtech 2 should have a fully-assembled width of 96.5mm. Road HT2 BBs should have a fully-assembled width of 91mm.

It won't be possible to fit SRAM 30mm cranks to a BB92-spec frame without permanently modifying the frame. There are various systems which use a 30mm diameter axle and greater lengths, including Rotor, Hope, and eThirteen.

GXP:

Many brands produce BB92/PF41 bottom brackets for GXP cranksets, but this combination is not common so many retailers won't have them in stock.

Hope offer converters to allow GXP axles to be used with their 24mm bottom brackets. These should not be used with Shimano BBs as they already have a plastic "top-hat" spacer between the bearings' inner casings and the axle, whereas Hope use bearings with a 24mm.

Answer 2

You can use a bb30 or pf30 crank (29.5mm) 30mm nominal spindle od crank on a 41mm id bb shell be it pf 89.5 or pf92 shell (91.5mm actual shell width)

I was researching this because I scored a pair of SRAM XO bb30 pf30 carbon cranks real cheap and was trying to find bearings for them for my next frame. I like narrow Q factors, so I was stoked on the bb30 idea.

I found adapter bb's that state fitment with most 30mm cranks, generally excluding SRAM cranks like mine, because "the SRAM cranks have too narrow of a spindle" well the spindle length on my cranks was like 90.5mm with the cinch ring in place all the way out, crank bolt tight. I was turning the cinch ring out, and I noticed its inner threaded race thing spun. So I pulled it off intact. now the spindle width is 96.85mm. I figure I can get one of the bb adapters now designed for other cranks, and just use a couple mm or so of thin spacers, maybe a wave spacer, to dial in the crank width without the gimmicky flimsy cinch ring.

The flanged sealed cartridge bearings that adapt the 41 shell to 29.5 (bb30) spindle have flanges, that I figure take up about 4mm so my SRAM cranks 96.85 minus 91.5 = 5.35mm. I'im assuming the flange thickness is going to be around 2mm, as long as it is not more than 2.675mm thick I should be able to fit these cranks to this frame without having to face the bottom bracket shell (or get different cranks).

Speaking of, facing a bb shell isn't the end of the world, although some chain guides may not like you doing so with an inboard crank spider or ring. We used to have to face bb's and head tubes regularly but it's not so common now. Most shops have the tool. IDK about facing carbon though, probably be just fiiiine.

problem solvers bb synopsis diagram https://problemsolversbike.com/files/tech/Bottom_Bracket_Standards_Reference.pdf

I suppose one could just get some bearings from your favorite bearing supplier, although it might be hard to find flanged 41od 29.5mm id bearing. I want a full ceramic angular contact one.