roadwise.Open study app

Minnesota driving lesson · Your Vehicle

Mirrors, tires, windows and upkeep

A 4-minute lesson from the Minnesota course. Read the rules and examples, follow the handbook page references, and check your understanding before you move on.

Study this lesson in the app Back to the course
Read time
4 minutes
Course unit
Your Vehicle
Checkpoint questions
6
Source pages
26, 27, 28

Mirrors and glass are how you see the road; tires are your only contact with it. Minnesota sets minimum standards for each, and a few quick checks keep you legal and safe.

Know the rule

All passenger vehicles must have rearview mirrors. Vehicles with no view through the rear window, like rental moving trucks, and pickup trucks used for hauling need an additional side mirror.

Handbook p. 26 ↗

Know the rule

Inspect tires for cuts, cracks, uneven wear, bald spots, bulges and punctures, and carry a good spare. Tires have less traction on gravel or dirt than on concrete or asphalt. Never drive on under-inflated tires.

Handbook p. 27 ↗
1 PSI

Air pressure a tire can lose every month

Handbook p. 27 ↗

Checking tire pressure

  • Find the recommended PSI on the sticker inside the driver's door or in the owner's manual
  • Check before driving or at least three hours after driving
  • Press a gauge into the valve stem to read the PSI
  • Compare with the door sticker or manual — not the PSI on the tire's sidewall
  • Let air out or add air until it matches the recommended number
Handbook p. 27 ↗
1/16 inch

Minimum legal tire tread depth

Handbook p. 27 ↗

The penny test

  • Hold a penny with Abraham Lincoln's body between your thumb and forefinger
  • Put Lincoln's head into the groove where the tread is lowest
  • If tread covers any part of his head, your tires are legal and safe
  • If not, your grip in bad conditions is greatly reduced
Handbook p. 27 ↗

Know the rule

Your view through the windshield and windows must not be blocked by cracks, discoloration, steam, frost, ice or snow. Don't hang objects between you and the windshield.

Handbook p. 27 ↗

Allowed on the windshield

  • Stickers allowed by law — state and national park, safety inspection stickers, EZpass devices
  • GPS and navigation systems mounted near the bottom
  • Driver feedback/safety-monitoring equipment just behind, slightly above or below the mirror
Handbook p. 27 ↗

Know the rule

Windshields can't be made more reflective or tinted to reduce light. Side or rear tint applied after Aug. 1, 1985 must show its light transmission and reflection. Tint passing less than 50 percent or reflecting more than 20 percent is allowed only on a pickup's rear window or the rear and side windows of a van, limousine or funeral home vehicle.

Handbook p. 27 ↗

Know the rule

A glass windshield needs working wipers, defrosters keep glass clear of steam and frost, and passenger vehicles need fenders or wheel guards to keep tires from throwing water and dirt.

Handbook p. 27 ↗

Save fuel

  • Keep the engine tuned, tires properly inflated and use the recommended oil grade
  • Combine errands; avoid speeding, rapid acceleration and sudden braking
  • Obey the speed limit and remove unnecessary heavy items
  • Use cruise control on the highway and overdrive gears
  • Use public transportation, carpools, rideshare, biking or walking when possible
Handbook p. 28 ↗

Put it into practice

Your door sticker says 35 PSI and the sidewall says 44 PSI maximum. After the car sat overnight, your gauge reads 31. Add air until it reads 35 — the sticker number, not the sidewall number.

Check your understanding

Read the question, decide on an answer, then open it to check the explanation. These are Roadwise study questions based on the source handbook.

Which vehicles need an additional side mirror beyond the standard rearview mirror?
  1. Pickups and trucks with no view through the rear window
  2. Any vehicle with tinted rear windows
  3. Any vehicle towing a trailer
  4. Convertibles with the top down

Answer: Pickups and trucks with no view through the rear window

Vehicles like pickup trucks and moving trucks, where the rear view can be blocked, must have an extra side mirror.

Handbook p. 26 ↗
A tire is considered illegal if its tread depth is less than what?
  1. One-eighth of an inch
  2. One-fourth of an inch
  3. One-sixteenth of an inch
  4. One-thirty-second of an inch

Answer: One-sixteenth of an inch

A tire with tread less than one-sixteenth inch deep is illegal.

Handbook p. 27 ↗
When performing the penny test, if any part of Lincoln's head is covered by tread, what does that mean?
  1. The tire needs to be replaced immediately
  2. The tread is below the legal limit
  3. The tire is under-inflated
  4. The tire is legal and safe

Answer: The tire is legal and safe

If tread covers any part of Lincoln's head in the penny test, the tire has enough tread and is legal.

Handbook p. 27 ↗
When is the best time to check your tire pressure for an accurate reading?
  1. Before driving or 3+ hours after driving
  2. Right after a long highway drive
  3. After at least one hour of driving
  4. Within 30 minutes after driving

Answer: Before driving or 3+ hours after driving

Tire pressure should be checked before driving or at least three hours after driving, when tires are cool.

Handbook p. 27 ↗
Window tint applied to side or rear windows after August 1, 1985, is restricted if it transmits less than what percentage of light?
  1. 50 percent
  2. 70 percent
  3. 30 percent
  4. 90 percent

Answer: 50 percent

Tint transmitting less than 50 percent of light (or reflecting more than 20 percent) faces placement restrictions.

Handbook p. 27 ↗
What must a vehicle with a glass windshield have in working order?
  1. A backup camera
  2. A tinted sun strip
  3. Windshield wipers
  4. A GPS mount near the bottom

Answer: Windshield wipers

A vehicle with a glass windshield must have working windshield wipers.

Handbook p. 27 ↗
Take the lesson checkpoint in the app

More in Your Vehicle

All Minnesota lessons