The question of what spacers-and how many- to use to fit a crankset to a bike with a Cane Creek bottom bracket is one that may sound confusing but is actually simple in practice. If you focus on your bottom bracket shell width, the added width of the bottom bracket cups, the "usable" spindle length of your crank, and your bike's optimal chainline then you can determine for yourself what combination of spacers you may (or may not) need.
1) Let's start with bottom bracket shell width as this is easy information to obtain. You can measure your BB shell or inquire through your bike's manufacturer. In the chart below (at the bottom of the page) you will see "Common Shell Widths" in millimeters.
2) Once you have your shell width then you will want to add to that your Bottom Bracket cup width. Cane Creek external Bottom Brackets add 22mm (11mm on either side). The PF 41/92 (our only internal BB) adds 4mm (2mm on either side) total.
3) The usable spindle width of your crankset is perhaps the most difficult part of this equation--largely because crank manufacturers use a variety of different lengths and neglect to publish this information--but you can figure this out by measuring the spindle width from the inside of the drive-side crank arm to the inside of the Preloader (or non-driveside crankarm). Let's take the eeWings MTN for example:
e.g. 1) In this example the usable spindle space is 98.25mm with the Preloader backed all of the way out and 93.25mm with the Preloader dialed all of the way inwards. Let's say we are trying to fit eeWings MTN to the Yeti SB 130. The SB 130 has a 92mm BB shell and we're using the Hellbender PF 41/92 so we would add 4mm to the shell width. At 96mm we are nicely in the middle of the "usable" spindle range.
e.g. 2) But what about Threaded BB's? Let's say we are fitting eeWings to the Evil Offering. That bike has a 73mm BB shell. The eeWings specify the use of a 2.5mm drive-side BB Spacer to be used with 73mm BSA BB's so we add 73mm + 2.5mm (BB spacer) + 22mm (BB Cup Width) and we arrive at 97.5mm. Would you look at that. We are nicely within the "usable" spindle range again!
4) But what about chainline? Once you figure out that your spindle will clear the BB cups then you need to get chainline correct. You do this through a combination of chainring offset and Spindle Spacers. Don't get too bogged down trying to get your bike's chainline purrfect. Modern drivetrains can cope with + or - 3mm of chainline imperfection without adverse effects to shifting performance.
Pro Tip: before swapping out your BB measure from a fixed point on the bike to the chainring (measuring from the chainstay is usually easiest). After you install the new BB make sure that the new position of the chainring matches the measurement you took with your previous setup.
*Spindle Spacers do not need to be specific to the manufacturer of the BB; they just need to fit the spindle diameter. 29mm DUB Spacers and 30mm Spindle Spacers can be purchased from a variety of manufacturers and in a variety of different widths.