Other mistake: Malloy is the training officer and Reed is the trainee for what appears to be years. A major part of training as a cop is to get hands-on training to drive in emergency situations, but Malloy always does, except when he has an invalid license or needs to move the car.
Log 51: A Jumper, Code 2 - S1-E19
Other mistake: Halfway through the show, the officers walk across the street to talk to some young toughs. The school sign painted on the street is spelled "Schol".
Log 54: Impersonation - S2-E16
Other mistake: They deal with the owner of a gym and his jersey says "Rivers" but the building says "River's". Is his name Rivers or River?
Credit Risk - S7-E10
Other mistake: Reed is running license plate numbers over the police scanner, looking for a hit-and-run culprit. The plate number he is looking for comes back on the radio as owned by a woman and is on a tan 1974 Ford sedan, but when the officers go to the woman's house and see the damaged car with that license plate, it's not a tan Ford, but a tan 1974 Chevrolet Caprice.
Answer: You probably need to be more specific about which car or episode you're talking about, but if I had to guess, it sounds like you're talking about "curb feelers." Most people have to park on the right side of the road (passenger side), so the wires or springs would make a noise when they hit the curb, letting the driver know they're close enough to the curb without hitting the tire against the curb.
Bishop73
S5 Ep5 "Training Wheels": Adam 12 stops a VW van. Their Matador car has a curb feeler on the left front of the car.
Correction: That's the right-hand side of the car.
Probably for one way streets. When they were popular, I saw them on front and rear. They were the mustaches and eyebrows of the day.