1994 BMW 318i steering wheel

1994 BMW 318i Mileage: 136,552 I've noticed that every time I make a turn the steering wheel or at least most of the time, I feel a light "clank" on the steering wheel. You can hear it sometimes but it's not that loud, I can hear because I know something is wrong. My friend told me it should be the bushing of the control arm. I really don't know what it is! My car is a '94 BMW 318i w/ 136552 miles and the motor is M-42. Another thing what's the difference between monotube shocks and twin tube shocks? Which one gives better performance, durability, etc.? -THANKS!!!!!