Why Rear-Mounted Spares Need More Protection Than Trunk Spares

Marko S.
Dec 3, 2025
3 min read

Not all spare tires live the same life. A spare stored safely inside the trunk is protected from the sun, weather, heat, and road debris. But a rear-mounted spare tire — like those found on Jeep Wranglers, Ford Broncos, Toyota RAV4s, Honda CR-Vs, FJ Cruisers, and many SUVs — faces harsh conditions every single day.

This is why rear-mounted spare tires wear out faster, dry-rot sooner, and absolutely require a protective cover. Here’s the full breakdown.

Rear-Mounted Spares Are Constantly Exposed to Sunlight

UV rays are the #1 cause of tire dry rot.

Trunk spares receive zero sunlight. Rear-mounted spares receive 100% sunlight.

Continuous UV exposure causes:

Fading
Drying
Cracking
Rubber hardening
Loss of flexibility

This process starts long before you notice it — and long before you ever need the spare.

A quality spare tire cover blocks UV rays and slows this damage dramatically.

Weather Hits Rear-Mounted Spares From Every Angle

Trunk spares stay clean and dry. Rear-mounted spares endure:

Rain
Snow
Ice
Road salt
Humidity
Sand
Wind
Heat waves
Freezing nights

This constant weather cycle accelerates:

Rubber breakdown
Internal weakening
Sidewall cracking
Tread deterioration
Wheel corrosion

A spare tire cover shields the tire from these harsh conditions year-round.

Rear Spares Heat Up and Cool Down More Rapidly

Trunk spares stay in a temperature-controlled space. Rear spares sit in direct sunlight, causing extreme temperature swings:

Hot days → tire heats rapidly
Cold nights → rapid cooldown
Winter → freeze cycles
Summer → heat buildup

These fluctuations cause the rubber to age faster.

Over time, this leads to premature dry rot — even if the tire has never touched the road.

Road Debris, Gravel, and Dirt Constantly Hit Rear-Mounted Spares

Trunk spares never see:

Gravel impacts
Road debris
Mud
Dust
Sand
Tar
Chemicals

Rear-mounted spares are exposed to all of these, especially on off-road vehicles.

Debris hits the tire at high speeds, slowly wearing down the rubber and damaging the finish.

A cover acts as an impact shield — much like a phone case for your spare.

Rear Spares Have Higher Risk of Rust and Hardware Damage

Exposed spares also expose:

Wheel bolts
Lug nuts
Mounting bracket
Camera wiring (Bronco, Wrangler JL)
Hinges and metal hardware

Moisture + road salt = rust.

Rust = weakened hardware.

A rear spare needs protection not only for the tire, but for the entire mounting system.

Rear-Mounted Spares Are More Prone to Theft

A rear spare is fully visible. A trunk spare is hidden.

Thieves prefer:

Visible
Quick-access
Uncovered
Unprotected

A spare tire cover:

Conceals the wheel
Hides the bolts
Makes the spare harder to remove
Reduces theft appeal

This is a simple but effective layer of security.

Rear Spares Age Faster — Even When They Look “Brand New”

Many drivers assume a spare is good because the tread looks new. But rear-mounted spares age from the outside in, not from tread wear.

A rear spare can be:

8 years old
Cracked
Dry-rotted
Sun-damaged
Unsafe

…even if it has full tread.

This is why tires have age limits, not just tread limits.

Why Rear-Mounted Spares Need a High-Quality Cover

A spare tire cover protects against:

UV rays
Heat
Rain and snow
Debris
Dirt and sand
Pollution
Road salt
Animal scratches
Fading
Dry rot

A high-quality, USA-made SpareCover® provides thick marine-grade vinyl, UV-resistant inks, reinforced stitching, and long-term protection for vehicles with exposed rear spares.