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Bought a bike with stripped/straight-threaded cranks, so they are useless, wanted help identifying this type of spindle so I can go online and order a new crankset.enter image description hereenter image description hereenter image description hereenter image description hereenter image description hereenter image description here

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This exact spindle style can be a little nebulous to speak and write about, because it's very common within BMX and a lot of cranks are compatible with it, but to my awareness it doesn't have one agreed-upon name. I think it's just one manufacturer that makes the cranks and spindles for it and it gets sold under about a million different brands, but I don't know the name of that company.

The standard is usually called 8-spline when it's called anything. There are two very common spindle diameters within BMX, 19mm and 22mm, and 8-spline is mostly associated with 19mm; I'm not sure if 22mm versions exist but they might. You should flip your tape measure around and measure the diameter to confirm yours is 19mm.

The way you're measuring implies you're concerned about the spline length, but on this standard the spline length doesn't count for much. This is not a press fit standard and the cranks can land anywhere along the splines. The crank locks into the splines using a pinch bolt. The bolts that go into the ends of this spindle style are for bearing preload only, and also provide a secondary form of security if something went wrong with the pinch bolt. Spindle spacers can be used freely with this spindle type to dial in the chainline, symmetry, and spline engagement. You want the end of each crank overhanging the end of the spindle by 0-2mm. Getting that part right is important and it's up to the person setting up the bike to make extra sure of it, because it won't just happen automatically when you put it all together.

This standard is the ubiquitous one for basic to medium quality BMX tubular chromoly 3-piece cranks, and many companies sell cranks that go on it. If it looks remotely the same and it's a cheap 19mm 3-piece, it's a match, again with the qualifier that sometimes in practice you need some 19mm BMX crank spacers to tune things in. (Part of the reason for this is that the rest of the bottom bracket hardware you have, i.e. the bearing shields, sprocket, and sprocket adapter as applicable, are less standard in thickness.)

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  • I just measured the diameter and its roughly 22mm, so if I searched "3-piece 8-spline single chainring BMX crankset", would the right products show up?
    – Keyin Liu
    Mar 18 at 1:28
  • You need to be sure about that measurement to get the right thing. I did some measuring in photoshop of the spindle against the ruler and it does look like more than 19mm, but I couldn't come up with 22. It could be 20mm, which is an odd but existent size. You're measuring the bearing contact surface or just the bearing ID itself. If it's 20mm then you're likely replacing the BB and spindle. A caliper is the right tool for the job, or hold up a metric ruler or tape measure against the BB bearing ID. Mar 18 at 2:07
  • No its definitely 14/16 of an inch, which is 22.225mm
    – Keyin Liu
    Mar 18 at 2:32
  • Also I don't currently have a caliper, metric ruler or tape measure, and the units that I am using are inches.
    – Keyin Liu
    Mar 18 at 2:35
  • Also, could this maybe be compatible with a Euro BB kit? I searched up the model that its supposed to be, and the website says that the stock bike came with a Euro BB Kithttps://99spokes.com/en-CA/bikes/rockymountain/2014/flow-pro#specs
    – Keyin Liu
    Mar 18 at 2:46
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I have only seen this spindle type on posh BMX and certain dirt jump style bikes with very strong steel cranks. A search for “BMX 3-piece cranks” will find you similar parts but you will probably need to use a new spindle (usually supplied) as well, as the splines differ between brands.

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