As used by most bikes. 2WD Two wheel drive. Avoids messing around with timing chains, which can be prone to falling off, and each rider can pick their preferred gear ratios and cadence. As a general rule of thumb, front suspension is more beneficial on SWB bikes, rear suspension more so on LWB bikes. Actually, rear suspension is good on all bikes.
Wheel sizes Recumbents come with a bewildering variety of wheel and tyre sizes.
Usually ISO 406 - the common BMX size. Sometimes something even more perverse. 540 and 541 are interchangeable. Which is nice. Usually ISO 559 - the common mountain bike size.