I have a Haro Steel Reserve 1.3 bike (https://archive.harobikes.com/mtb/2016-mtb/steel-reserve-1-3-2016) with "Chromoly 2-pc 8 spline cranks". I am looking to replace said crank. I have my eyes on the BSD Substance (https://eu.bsdforever.com/products/substance-cranks) but am unsure how to gauge whether or not it will fit. I tried looking up details for my existing one but I don't know what to look for.
What should I look for in order to ensure compatibility?
From the spec sheet you know it's a Euro shell, which is the BMX/DJ way of saying BSA/ISO 68mm.
The cranks you want are a 22mm 48 spline spindle, so they need pairing with a 22mm Euro BB.
The crankset you have is described as "Haro chromoly 8 spline 2-piece crankset w/ 25t sprocket." It's not clear what spindle size it is or what it's got for spacers.
Remove your cranks and measure the spindle to see if it's 22mm. If it is, you can probably re-use your existing BB, but you may potentially need more (or less) spacers to get the spline engagement correct on the new crank. Alternatively, start fresh and buy a 22mm euro BB of the sort that starts with a thin cup profile and includes a bunch of spacers to dial the Q, chainline, and spline engagement as needed. Since the mid BB made for your new crank comes with a number of spacers, it's likely you need them in a euro installation as well. Or, you could make life easy and just ask the company what euro BB they recommend be paired with the crank you're getting.
