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 1: The Impossible Mission - S1-E1
Character mistake: They turn left onto Moorpark St and they say into the radio they are going east on Moorpark. However, the street sign shows they are going west. (00:10:30)
Log 1: The Impossible Mission - S1-E1
Deliberate mistake: Halfway through the episode, they are chasing car thieves in a drainage channel. The thief's car comes to the end of the road and crashes into a deeper gully. You can see that the windshield has been taken out of the car, although it was previously there. They cut away and when they come back, parts of the windshield are back in the car, but the whole center is missing.
Visible crew/equipment: When Reed asks Walters how many kids he has, the moving boom mic casts a shadow on the lockers at the top, left side of the screen. It appears again a few shots later. (00:00:50)
Continuity mistake: In the opening scene, an officer is yelling at Reid for trying to give him a dog. There's a gun belt hanging on the locker next to Reid, Malloy comes in and it's still there. Next angle, it's gone.
Continuity mistake: The unit says 1w20 then later says 1w30. (00:25:40 - 00:26:40)
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
Continuity mistake: When Reed and Malloy go to the boxing gym's office the first time, the name on the door's glass window is spelled as "Fredie" and he's the owner and manager, but in the end credits James McEachin's first name is listed as "Freddy." (00:03:15 - 00:24:15)
Log 54: Impersonation - S2-E16
Visible crew/equipment: While Malloy and Reed are outside the Commander's office Malloy asks Forest about his son, and as Forest walks away we can see the actor's L-marker taped to the floor. (00:06:40)
Log 54: Impersonation - S2-E16
Visible crew/equipment: After Pete and Jim arrest the "second story men" for burglary, when Forest stops and asks, "What's the scoop?" the actor's T-mark is visible on the floor. (00:14:50)
Log 54: Impersonation - S2-E16
Visible crew/equipment: When Pete and Jim bring Freddy to the jail cell to identify the criminal, there's a T-mark taped to the floor near Jim's feet. (00:23:50)
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?
Revealing mistake: Halfway through the show, the officers get a flat. As Malloy is getting ready to jack up the car, Reed starts using the lug nut wrench to loosen up the nuts. He repeatedly turns the wrench clockwise, which would tighten the nuts.
Continuity mistake: About 3 minutes in, Malloy is practicing driving on a course with an instructor. Most of the outside shots show only a driver in the car.
Van Nuys Division: Pete's Mustache - S6-E7
Continuity mistake: The officers are leaving the station on patrol. There's a police car parked in the outer lane of the exit. Next shot, they're driving out of the same lane, and the car is gone.
Factual error: 19 1/2 minutes in. They pull over a car and run the plate. Malloy tells the driver the car is registered to a Volkswagen. He should have said the plate is registered.
Visible crew/equipment: In the scene showing Officer Malloy shortly after he enters the inside of the supermarket, a crew member is visible in a back room/hallway of the supermarket.
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.