Last updated on March 20th, 2023 at 12:46 pm
In this article, you will learn how much air pressure should be in a spare tire along with other important information.
If you ever had a flat tire on your vehicle, you know how frustrating and inconvenient it can be. Not having a spare tire in your car can turn a bad day into a really bad day.
A spare tire is normally kept in the trunk of your car or mounted to the undercarriage and is used in the event of a blown or flat tire.
A flat tire is not something that gets checked very often. When was the last time you checked the air pressure in your spare tire?
You should always ensure that your vehicle has a spare tire inflated to the right pressure that can be swapped into place if one of your normal tires goes flat.
A flat spare tire won’t be much help to you.
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How Much Air Pressure Should Be In A Spare Tire?
A spare tire is often called a donut tire which is smaller than the vehicle’s regular tires. The air pressure of the spare tire should be around 60 pounds per square inch (PSI) which is more than the regular-size tires which are between 30 – 40 PSI.
If you have a spare tire and the pressure is not exactly 60 PSI, the tire will still be suitable to drive on until you reach the nearest service station for repairs.
If your vehicle has a spare tire that is the same size as the normal tires on the car, it should only be inflated to the same pressure as the others.
If your regular car tires have an operating pressure of 32 PSI, then your full-size spare should be at 32 PSI as well.
Why do spare tires have higher PSI?
As mentioned, a spare tire is much smaller than a regular tire. Because of the reduced size, the tire has less contact with the ground.
The higher PSI is needed to compensate for the reduced tire area and helps make up for the size reduction. It also increases the tire tread’s contact with the ground.
Over time, the air pressure in the spare tire will deplete as it sits in the trunk unused. If you have 60 PSI in the tire when placed in the trunk, chances are it will have less when you need it someday.
Always check the air pressure periodically and adjust as necessary.
How far can you drive on a spare tire?
Not all spare tires are identical but on average, it is recommended to only drive on a spare tire for around 50 – 70 miles. 50 miles is considered to be the maximum distance and only drive up to 70 miles if you absolutely must.
A spare tire is only meant to get you from your current location to the closest repair shop or somewhere where it can be properly replaced.
How fast can you drive on a spare tire?
There is also a speed limit for a spare tire of 50 miles per hour (MPH). A spare tire is not designed to travel at high speeds and for safety reasons, you should keep your speed under 50 MPH.
Remember the 50/50 rule.
Drive on a spare tire for no more than 50 miles at a speed under 50 MPH.
What are the dangers of driving on an under or over-inflated spare tire?
If you drive on a spare tire that is either under-inflated or over-inflated, there are dangers involved.
- When a tire is over-inflated it bulges in the center causing less ground contact between the tire and the road.
- There is also an increased risk of losing control of the vehicle.
- Over-inflated tires can cause increased wear reducing their life span.
- Over-inflated tires can be damaged easier due to potholes and curbs.
- Higher risk of a blowout with an over-inflated tire.
- Under-inflated tires can cause excess contact with the road surface causing friction and heat which can lead to a blowout.
- Under-inflated tires can lead to less control of the vehicle.
A spare tire should never be under or over-inflated due to the dangers involved.
How to check the air pressure of a spare tire?
Checking the air pressure of a spare tire is the same as checking the air pressure of a regular tire.
Digital tire gauges are more common these days although some people still prefer the older analog gauge. Both work fine and are effective when checking tire pressure.
Start by unscrewing the cap from the valve stem. Press the gauge fitting onto the valve stem firmly. Then read the pressure on the gauge.
You should check the spare tire’s air pressure often. A good rule of thumb is to check it when you have your tires rotated or around 3000 miles which can be a few months for some people.
Where to find the proper air pressure of a spare tire?
Before adding air to the spare tire, always check to confirm how much air to put in. As mentioned, it should be around 60 PSI. There are a few places where you can find this information.
- The vehicle’s owner’s manual.
- The sticker on the driver’s door.
- On the tire itself.