The Disappearing Spare Tire
A generation ago, nearly every vehicle came with a full-size spare tire mounted on a matching wheel in the trunk. Today, many vehicles are sold with compact temporary spares, tire repair kits, or no spare at all. Understanding the different spare tire options helps you prepare for the inevitable flat tire and make informed decisions about what your vehicle should carry.
Full-Size Matching Spares
A full-size matching spare is identical to the four tires on your vehicle, mounted on the same type of wheel. This is the gold standard of spare tires because it maintains your vehicle's handling balance, allows normal driving speeds, and can be used indefinitely as a regular tire. You can simply mount it and continue driving without restrictions. Many full-size trucks, SUVs, and some sedans still include full-size spares, often mounted beneath the vehicle or in the cargo area.
Full-Size Temporary Spares
Some vehicles include a full-size spare mounted on a less expensive steel wheel rather than the alloy wheels used for the other four positions. This tire is the same size and specification as the rest but on a cosmetically different wheel. It functions identically to a matching spare and can be driven without restrictions. The lighter, cheaper wheel keeps costs down while providing full spare tire capability.
Compact Temporary Spares (Donuts)
Compact temporary spares, commonly called donuts, are smaller and narrower than the vehicle's regular tires. They typically use higher inflation pressures, around 60 PSI, and have strict speed and distance limitations, usually 50 MPH maximum and 70 miles of driving. They are designed to get you to a tire shop, not to serve as a long-term replacement. Their smaller size saves trunk space and reduces vehicle weight, which is why automakers increasingly favor them.
Limitations of Compact Spares
Driving on a compact spare affects your vehicle in several important ways. The smaller diameter changes the effective gear ratio, making the speedometer inaccurate and potentially confusing the anti-lock braking system and stability control. The narrower width reduces grip, particularly in wet conditions. Traction control and all-wheel-drive systems may behave differently with mismatched tire sizes. Extended use of a compact spare can damage differential gears in all-wheel-drive vehicles.
Tire Repair Kits and Inflators
Many modern vehicles, particularly EVs and small cars, have eliminated the spare tire entirely, replacing it with a tire sealant kit and portable air compressor. These kits inject sealant through the valve stem to plug small punctures, then inflate the tire to a driveable pressure. They work for minor tread punctures but cannot repair sidewall damage, large gashes, or blowouts. They also contaminate the tire's interior, potentially making a permanent repair more difficult.
Run-Flat Tires as Spare Alternatives
Some vehicles use run-flat tires instead of carrying a spare. Run-flat tires can travel up to 50 miles at 50 MPH after a complete loss of air pressure, giving you time to reach a repair facility. This eliminates the need for spare tire storage space entirely. However, run-flat tires are more expensive to replace and generally provide a firmer ride than conventional tires.
What Should You Carry?
If your vehicle has space for a full-size spare, it is the safest and most versatile option. If your vehicle came with a compact spare, keep it properly inflated and know its limitations. If your vehicle has only a repair kit, consider adding a compact spare if one is available for your model. Regardless of what you carry, check your spare tire pressure at least twice a year as spare tires lose air over time even when unused.
Ship.Tires Spare Tire Solutions
At Ship.Tires, we can help you find the right spare tire solution for your vehicle. Whether you need a replacement compact spare, want to upgrade to a full-size option, or need a tire repair kit, we have options available. We also carry the correct wheels for spare tire applications and can advise on the best solution for your specific vehicle and driving needs.