By Norman Ford · Updated October 2026
Semi truck mirrors: types, adjustment, rules and replacement
A truck driver sees the world behind and beside the rig almost entirely through mirrors. Cracked glass, a loose bracket or a poorly aimed mirror leaves a gap where a car can disappear. Mirrors are cheap to fix and important to get right.
Types of truck mirrors
Tap each mirror to see what it covers.
Tap a numbered balloon for the part's job, check and spec.
| ITEM | PART | WHAT IT DOES | CHECK |
|---|---|---|---|
| 1 | Flat main mirrors | Show an undistorted view along the side of the trailer and the lane behind. | Aim so the trailer's side just appears on the inner edge. |
| 2 | Convex spot mirrors | Curved mirrors that show a wider area, including the lane beside the cab. | Objects look smaller and farther away than they are. |
| 3 | Hood or fender mirrors | Mounted on the hood or fenders to show areas beside and in front of the cab. | Secure mounts; aim to cover the front corners. |
| 4 | Heated and powered mirrors | Heat clears ice and fog; power adjustment helps set mirrors from the seat. | Heater and motor operation, especially in winter. |
| 5 | Camera systems | Cameras and monitors that add views of blind spots, or replace mirrors where permitted. | Clean lenses and working screens. |
Adjusting mirrors
- Set the seat first in your normal driving position.
- Main mirrors: adjust so you can just see the side of the trailer along the inner edge, with the rest showing the lane beside and behind you. The horizon should sit roughly in the upper part of the mirror.
- Convex mirrors: aim to show the area beside the cab and down toward the lane, overlapping with the main mirror's view.
- Hood mirrors: aim to show the front corners and the area beside the bumper.
- Check with a walk-around or with a helper standing in the blind spots.
Adjust again whenever another driver uses the truck, and check mirror aim during every pre-trip. Mirrors are knocked out of position at docks and truck washes.
The rules
Federal rules in 49 CFR 393.80 require trucks to have rear-vision mirrors on each side, positioned to show the highway to the rear along both sides of the vehicle. Cracked or broken mirrors are common inspection findings.
Source: 49 CFR 393.80, checked October 2026
Blind spots
Large trucks have blind spots in front of the cab, beside the cab (largest on the passenger side), and behind the trailer. Mirrors reduce but do not remove them. Good habits help: check mirrors every few seconds, signal early, move slowly when changing lanes and use a spotter or get out and look when backing.
Camera systems
Many trucks now have side and rear cameras to cover blind spots. Camera monitor systems that can replace mirrors have been allowed for some trucks under federal exemptions with conditions. If you use cameras, keep lenses clean and confirm the screens work during the pre-trip.
Mirror maintenance and replacement
- Clean mirrors daily; dirt and road film reduce visibility, especially at night.
- Check brackets and mounting bolts for looseness and cracks.
- Replace cracked glass promptly.
- Check heated mirrors before winter.
- Use replacement mirrors and glass made for your truck model.
Mirror glass can often be replaced separately from the housing. Brackets damaged by impact should be replaced, not bent back.
Mirrors in the walk-around
Mirrors are part of the daily inspection along with lights and the cab. Our guides to semi truck lights, the semi truck interior and semi truck wheel covers cover nearby items, and the pre-trip inspection checklist includes the mirror checks. For damaged mounts or electrical faults, see our guide to semi truck repair.
Mirror types by truck
Different trucks use different mirror setups. Conventional tractors usually have door-mounted main and convex mirrors, often in one housing, plus hood or fender mirrors. Cab over trucks often carry large mirror arms with several mirrors, and a downward-looking mirror above the passenger door to show the area directly beside the cab. Box trucks commonly have large West Coast style mirrors on long arms, sometimes with a front cross-view mirror to see directly in front of the bumper.
Setting mirrors for backing
Backing into a dock or a tight space relies heavily on mirrors. Many drivers tilt the main mirrors down slightly before backing to see the trailer's rear wheels and the ground, then return them afterward. Powered mirrors make this easier. Whatever the setup, get out and look when unsure; a mirror shows only part of the picture.
Night driving and mirrors
At night, glare from headlights behind can be a problem. Keeping mirrors clean reduces glare from dirt and film. Some mirrors have tinted or auto-dimming glass. Avoid aiming mirrors so they catch lights directly; a slight adjustment can reduce glare while keeping the view you need.
Winter mirror care
Ice, snow and road spray can blind mirrors quickly. Heated mirrors clear ice and fog, but the heaters can fail; test them before winter. Carry a scraper and a cloth, and clean mirrors at every stop in bad weather. Make sure mirror heater wiring is intact, since it runs through the door hinge area and can be damaged.
Replacing mirror glass
Many mirror heads let you replace just the glass, which is cheaper than a whole mirror assembly. Heated glass has wires that connect to the heater circuit. Match the glass to the mirror model and type: flat or convex, heated or not. Install carefully so the glass sits flat and secure.
Mirror brackets and vibration
Mirrors that shake at speed are hard to read and can loosen over time. Check that brackets, arms and mounting bolts are tight, and look for cracks where arms attach to the cab. Worn mirror arm bushings can let mirrors droop. Fix vibration early before a mirror comes loose on the road.
Mirrors and inspections
Cracked mirrors and missing mirrors are common inspection violations. A quick look at each mirror during the walk-around, plus a check of the view from the driver's seat, catches most problems before they become violations.
Convex mirror distortion
Convex mirrors show a wider area, but objects look smaller and farther away than they are. Drivers learn to use convex mirrors to spot vehicles and the flat mirrors to judge distance. Before changing lanes, check both, and remember a vehicle in the convex mirror may be closer than it looks.
Mirrors and cameras together
Many drivers use cameras as an extra set of eyes, especially for the passenger side and for backing. Cameras work best when lenses are clean and screens are positioned so the driver does not have to look away from the road for long. Mirrors remain the primary tool on most trucks.
Choosing replacement mirrors
When a whole mirror assembly must be replaced, match the truck model, mounting points, and whether the mirror is heated, powered or both. Aftermarket assemblies can save money, but check that they mount solidly and give the same field of view as the original. A mirror that vibrates or sits in a different position can leave a new blind spot.
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