The frame I am buying has a pf92, which is also apparently BB89/91.5.

The first figure I think matches what hope call pf46, but doesn’t match the second figure.

The second figure is apparently the shell width, but that doesn’t match any crank axle lengths.

The shop I emailed said I can’t fit a bb30 crank because it wouldn’t be wide enough, but from what I can see, bb30 cranks come in the same axle length options as 24mm cranks, ie 68, 73 & 83.

Where am I going wrong, it shouldn’t be this bloody difficult. Whey can’t they just give decent information on their website with BB and cranks specs.

and might I add arghhhhhhhhh!!!

I’m not going to claim to understand BB standards, but the frame you’re buying will take a standard 24mm axle crankset.

BB30 would need a bigger hole (30mm).

You should be pleased about this!

I don’t see a 30mm axle as a disadvantage, in fact I would have preferred it (it gives more options for power meters, although I will probably never fit one).

You can put a 30mm axled chainset in pf92 (41mm id) BB shell -with the correct BB.But not a BB30 one…well sort of,BB386 Evo (longer spindle).

Park Tools

I thought I did but looking at that chart, I wouldn’t have a clue now. Good job my bike is a normal, threaded BB 😯

The shop I emailed said I can’t fit a bb30 crank because it wouldn’t be wide enough, but from what I can see, bb30 cranks come in the same axle length options as 24mm cranks, ie 68, 73 & 83.

68 etc is the bb width not the axle length.

Where am I going wrong, it shouldn’t be this bloody difficult. Whey can’t they just give decent information on their website with BB and cranks specs.

and might I add arghhhhhhhhh!!!
What do you have and what do you want to fit?

Sorry to hijack…. Rorschach have you had any emails from me ref your Pikes?

What do you have and what do you want to fit?

Well as yet I have nothing, I wanted to fit a hope BB and a sram x01 BB30 crankest. Although that may not be possible, and might mean going gxp for the crankset, although I don’t quite understand why when the same axle lengths (shell widths) are available for both bb30 and gxp?

Main aim is to have a quality BB, that doesn’t creak and/or need replacing every few months, hope fits the bill and I already have a hope press fit BB tool.

I want a crank set that I can fit a relatively small direct mount (28 tooth AB ovalised) chainring to when required.

Normal BB shells are 68 or 73. You ad either 7.5mm or 2.5mm of spacers to that, which takes them to 73.5. THen you fit an external BB, which takes then to….about 92mm wide.

Your BB92 has a shell that’s 92mm wide (roughly, there are spacers and washers in play) – the bearings sit inside that 92mm.

In both cases, the axle needs to be more than 92mm for the crankarms to sit outide the bearings.

Ordinary Shimano/RaceFace/Sram 24mm cranks are wide enough, and new gneration 30mm RaceFace Cinch/Hope/E13 etc are all wide enough too, so with the right BB, they fit BB92.

BB30 axles are <92 so they don’t play.

although I don’t quite understand why when the same axle lengths (shell widths) are available for both bb30 and gxp?

Because;

a BB30 bottom bracket has the bearings inside the shell.
a gxp (and HT2 and others) has bearings outside shell.

Hence bb30 axle length between arms is the shell width, 73mm on MTB.
Gxp axle length between arms is shell width PLUS bearings, so about 92mm on MTB (standard 73mm BB width)
Some BB standards take that gxp setup and integrate the bearings into the frame, but obviously keep the same dimensions so the cranks fit, ergo you get a PF92 frame.

Its worth pointing out though, no one talks about axle lengths anymore. Its not like square taper where you buy in 1 or 2mm increments to suit. You buy the right crank for the BB, or you buy the right BB to fit your crank to your frame, there are not really any variations like in the old way.

PF92 aka BB91aka PF41 is a 41mm ID shell x 91 wide and commonly used with 24mm spindle cranks

PF46 aka PF30 is a 46mm ID shell available on a range of widths from 68mm upwards

BB30 aka PF42 is a 42mm ID shell typically 68 or 73mm wide.

The latter 2 are typically used with a crank with a 30mm spindle and 61806 bearing but you can use adaptor BBs for HT2, GXP etc

A regular BB30 crank won’t fit a PF91 shell because there’s simply no room for the bearings, however you can get a longer spindle crank like a Rotor which places the bearings outboard, but they are weenie/ not very durable.

What type of cranks are you trying to fit?

PF92 aka BB91aka PF41 is a 41mm ID shell x 91 wide and commonly used with 24mm spindle cranks
…
A regular BB30 crank won’t fit a PF91 shell because there’s simply no room for the bearings, however you can get a longer spindle crank like a Rotor which places the bearings outboard, but they are weenie/ not very durable.

I think this effort from Hope allows 30mm cranks in a PF92 BB? Not tried it myself though, so don’t know what cranks will fit it width-wise. Presumably the Hope ones will.

I had the same question as the OP a few years ago but I ended up going for SRAM 24mm GXP cranks in a PF41 Hope BB in PF92 because the 30mm option wasn’t available then. GXP in PF41 works fine for me.

Another reminder of why I’m so glad I gave press-fit bottom brackets a swerve, when I built my last bike.

“The thing that I love, about standards, is that there are so many to choose from”

To be fair PF92 is the best of the bunch and seems pretty reliable now as well as working with normal cranks.

Is it a Trek? If so, I emailed them asking what BB to use in mine and they said “****ed if we know, BB standards are confusing eh!”

I have a couple of bikes with BB86/91 and found it works reliably with a 24mm spindle crank. BB30 cranks are designed for narrower 68 or 73mm shells with inboard bearings – you can’t install a pair of 68mm long spindle cranks inside an 86mm BB shell. You can get cranks with longer spindles e.g. Rotor, but the bearings are still weenie / not very durable.

Is it a Trek?

Yep, trek have been useless, but I am top of what I need now (thanks dovebiker) means I need to get a gxp x01 crank instead of a bb30, which is a shame as I already have a few AB oval rings for a bb30 x01 crank.