Compatibility of 41mm x 107mm bottom bracket shell

Question

Hi I have spent several days looking for a bottom bracket and crank. At this point it seems that there is nothing but 1 traditional pressfit bottom bracket and 1 crank that fit this shell. However, I want to make sure that nothing else fits before giving up.

Bottom bracket shell dimensions: 41mm internal diameter and 107mm width

Type: press fit (non-threaded)

Do threaded-together bottom brackets for this shell exist? This means, a bottom bracket that is not pressed into the non-threaded shell, but each cup screwed into the other cup, like the image:

The reason being that pressfit bottom brackets mis-align in time and start creaking quite fast. Then it becomes and endless buying of bb every few months. I have experienced it with my road bike. Threaded-together BB (or whatever name they have) do solve the problem.

Regarding the crank, it seems that the only crank that fits a 107mm BBshell is the Truvativ Hescendant DH, which is the only one that has in the description this BB.

Any regular MTB crank's spindle will be too short, is that correct? I do not know the length of the crank's spindles, it is never mentioned anywhere, as if there was only 1 length.

Thanks in advance.

*Edited because it seems it was not clear.

Answer 1

Looks like what you bike is intended for is a 'BB107' or 'PF41x107' BB, that is a BB86/92 widened to 107mm. See https://wheelsmfg.com/bb-standards. It seems this was intended for downhill bikes, so look for downhill specific cranks.

You are correct that cranks specified for 83mm or narrower shells will not fit in your 107 mm shell as the spindle will be to short.

Product recommendations are off topic here but note I was able to find out that Praxis makes a downhill crank that has a PF41x107 option: https://praxiscycles.com/product/dh-crank/. I believe Praxis uses what they call an 'M30' spindle which fits in their own BBs, but they make a BB that will work with PF41x107.

Also, Wheels manufacturing makes a PF41 thread-together BB for fat bikes that works in 105-132mm shells and 24mm Shimano or 24/22mm SRAM GXP axle cranks.

Again, not product recs but just to show there are options out there.

BTW, I have had success installing press-fit BBs and eliminating creak using Park Tool's RC-1 press-fit retaining compound.

Answer 2

Your frame is only compatible with bottom brackets that are connected with the frame using the press-fit interface of the right dimension (there are many standards - open or proprietary). Threaded bottom brackets are screwed into the frame and are not compatible with your frame.

What you have in your picture is a press-fit bottom bracket as well, not threaded and it may or may not creak. One cannot say in advance whether a press-fit bottom bracket will creak in your frame or not. It depends on the quality of the alignment of the bottom-bracket shell in your frame. The threaded sleeves inside of the bottom bracket ("thread-together BB" as Weiweg Ng commented) in your picture may or may not help with that, one cannot say in advance.

When it comes to the allowable cranksets, you just have to follow the specifications. The manufacturer always says to which bottom bracket shell width they can be used as discussed in Picking a crankset for a 107mm BB on a downhill bike . Cranksets like the Praxis downhill cranks or Shimano FC-820 or FC-825 (but these are 104 mm) might be applicable, provided you frame can accept the respective required BB (here BB107 Shimano SM-BB71-41C ). There should be more alternatives around.

Answer 3

What you're running into is that most cranks that go in this shell are going to say 83mm in their descriptions, not 107mm. Manufacturers of such cranks will not necessarily spell out that they're compatible with 107.

A useful way of thinking about it is that PF107 (what you have) is to an 83mm threaded downhill bike shell as PF92 is to a 68/73mm threaded shell. The bearing face-to-face measurement is the same as what a crank for an 83mm shell wants. It's just getting there by having a bearing that sits nearly flush with the edge of the shell, as opposed to an external cup. It is correct that most mountain cranks will not work because their spindles will be too short.

Thus, your options for cranks are:

• All 2-piece cranksets intended for 83mm threaded shells with conventional external bearings. There are many options. For this you're using whatever PF107 BB is needed that's compatible with the crank choice in question. For example if you used Saint or Zee 83mm cranks you'd get a Shimano PF107 type BB for a 24mm spindle, or if you got DUB 83mm cranks you'd get the SRAM DUB BB for PF107.
• Most iterations of 30mm spindle cranks with interchangeable spindles have a spindle that will go in this shell. Raceface Cinch and Cannondale SI are examples of this. (Raceface makes it more complicated yet by relating it to the hub width/chainline and not the shell, but whatever). If you want to be safe you'd use whatever BB the crank maker in question says for a PF107 shell, but there is also some interchangeability with these sorts of cranks. One of the confusing things is that some PF92 BBs for long 30mm spindles would work and some wouldn't, depending on whether their dust shield uses a fixed length or two-pieces-telescoping-into-each-other type design.

As for what thread-together BBs are available that would work, that is exactly the kind of rapidly changing shopping advice we try to avoid here.