How Weather Affects Your Spare Tire (Sun, Snow, Salt & Heat)

Marko S.
Dec 3
3 min read

If your vehicle has a rear-mounted spare tire, it’s exposed to weather 24/7. Most drivers forget about it — but sun, snow, salt, rain, and extreme temperatures are constantly damaging the rubber, even when the tire is brand new and never used.

This guide breaks down how each type of weather affects your spare tire and why proper protection is essential.

Sun Exposure (UV Rays) — The #1 Cause of Tire Dry Rot

Nothing destroys a spare tire faster than sunlight.

UV rays cause:

Dry rot
Sidewall cracking
Fading and discoloration
Rubber hardening
Loss of flexibility

The top of the tire takes the most UV damage, which is why cracks often start there first.

Without a cover, a spare tire can become unsafe long before you ever use it.

Heat — Accelerates Rubber Breakdown

When a tire sits in direct sun, it absorbs heat quickly.

Rubber expands, softens, and loses essential oils.

Heat causes:

Faster aging
Brittle, dry rubber
Surface cracking
Internal weakening
Air pressure fluctuations

Warm climates, desert heat, and strong sunlight dramatically shorten a spare tire’s lifespan.

A cover reduces surface temperature by blocking direct heat absorption.

Snow & Ice — Create Moisture Stress and Freeze Damage

Cold weather may seem harmless, but it’s not.

Snow and ice cause:

Freezing and thawing cycles
Moisture buildup
Micro-cracking
Loss of elasticity
Stiff, brittle rubber

Repeated freeze-thaw cycles weaken the tire from both outside and inside.

Rear-mounted spares face this every winter.

A tire cover shields the tire from snow impact and helps reduce freeze stress.

Road Salt — Corrodes Wheels and Damages Rubber

Winter salt is one of the most destructive forces on your spare tire and wheel.

Salt exposure leads to:

Corroded rims
Rusted bolts and brackets
Stained rubber
Accelerated aging

Once metal hardware starts rusting, the spare can become difficult or impossible to remove.

A cover keeps salt and slush off the tire and wheel.

Rain & Humidity — Encourage Dry Rot and Moisture Damage

Moisture affects tires in several ways:

Weakens rubber bonding
Increases dry rot risk
Gets trapped between the tire and wheel
Causes mildew or staining
Rusts hardware over time

Vehicles in rainy, coastal, or humid regions see much faster spare tire aging.

A waterproof marine-grade vinyl cover prevents constant moisture contact.

Wind-Blown Debris — Hits the Tire at Highway Speeds

Exposed spare tires are constantly struck by:

Sand
Gravel
Dirt
Dust
Branches
Road debris

These impacts cause:

Surface wear
Cuts and scratches
Abrasion spots
Rubber pitting

A tough vinyl cover absorbs debris instead of your tire.

Extreme Cold — Makes Rubber Hard and Fragile

Rubber loses flexibility in cold climates.

A spare tire exposed to freezing temperatures can become:

Stiff
Hard
Brittle
Prone to cracking

This damage isn’t always visible from the outside.

A cover helps insulate the tire and maintain more stable surface conditions.

Coastal Weather — Salt Air + Sun = Rapid Aging

Vehicles near the ocean face:

Salty air
High humidity
Intense UV
Constant moisture

This combination is extremely harsh on tires and accelerates dry rot dramatically.

A marine-grade cover is essential in coastal regions.

Off-Road Conditions — Dust, Mud, and Vibration Wear

Spare tires on off-road vehicles (Wrangler, Bronco, FJ Cruiser, Hummer, etc.) face:

Constant dust clouds
Mud splashes
Trail debris
Heavy vibration

These conditions quickly wear down exposed rubber.

A heavy-duty cover protects the spare even during trail use.

Why a Spare Tire Cover Helps Against All Weather Conditions

A high-quality spare tire cover protects against:

UV rays
Heat
Rain & humidity
Snow & ice
Road salt
Coastal air
Sand & debris
Freezing temperatures

Marine-grade vinyl (like SpareCover® uses) is specifically designed for harsh outdoor exposure. It prevents dry rot, cracking, fading, and aging — extending the life of your spare for years.