I’m trying to get into Zwift and the Smart Hub seems perfect for me. But I want to make sure I get a compatible bike, ideally something inexpensive and bought used locally. Most bikes for sale that I would prefer (mountain or hybrid) are 21-speed (3x7). I know I can get a 7-speed cassette if I make sure it has the right teeth, but I’m not sure if 3x drivetrain would cause issues.
I’m trying to find a used 1x8 - 1x12 bike to avoid all this and just use the included Smart Hub cassette, but most of the people selling them used have no idea what kind of gearing they have. Lots of 21-speeds being advertised as 10-speed. I really just want something basic in the bike category.
No the Hub does not require a 1x drivetrain. Most people use road bikes with 2x drivetrains with indoor trainers to achieve wider gear range with more gear choices and a bigger high gear. Whether you need a big high gear depends on how strong you are and if you plan to sprint on the bike. 1x bikes sometimes come with a very small chainring which can be problematic for getting adequate resistance out of the trainer. A 3x drivetrain will work fine. Putting a 7 speed cassette on the Hub will require an additional spacer under the cassette. Some older bikes with 7 cogs in back also have 126mm axle spacing which is too narrow for modern direct drive trainers. Those bikes will mostly be from the 1980s. Most newer bikes with a 7 speed cassette will have wider axle spacing and will work fine.
Thank you @Paul_Southworth ! I should have just asked here first because I kept going in circles trying to find that information myself.
I debated this as well with my 30T 1X crankset MTB, I opted to buy a used road bike with 2x Crank and 9sp cassette.