rumbling of vehicles, threshold
轔 centers on the deep, resonant sound of vehicles in motion, especially the rumbling of wheels. The threshold sense is a rare, possibly archaic extension, perhaps from the idea of a carriage crossing a threshold with a rumble.
轔 combines 車 (vehicle) with 粦, which likely provides the sound and may relate to a rumbling or rolling noise. The exact historical development of 粦 is uncertain, but the character is clearly a phono-semantic compound.
A vehicle 車 with a complex rumbling part 粦: imagine a heavy cart rolling over cobblestones, making a deep rumbling sound.
For リン, picture a rumbling vehicle with wheels that ring like a bell: ring -> リン, and the sound resonates as it crosses the threshold.