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What Are Valve Stems?
Valve stems are small devices that allow a vehicle owner to add or remove air to a tire. Valve stems look like short, little, rubber straws that stick out from your tire. They are usually black, and they come with a valve cap which protects the stem from dust and dirt.
Valve stems hold air in the tire through the use of a Schrader valve, which is a spring loaded valve. When air is added through a valve stem, the spring compresses, and lets air in.
Once air is no longer applied, the spring shuts the valve closed and holds the air inside the tire.
Valve stems allow a person to maintain good tire pressure since they can adjust the air pressure to the correct amount without having to take it to a shop.
While valve stems seem small, they are essential to the tire since, without them, adding or letting out air would be impossible.
Do Tires Come With Valve Stems?
Tires do not come with valve stems. Tire shops buy a case of valve stems and keep them in the shop. When someone comes into the shop to buy new tires, a valve stem is added into the tire at the same time the tire is mounted onto the rim.
Valve stems are very cheap. You can purchase 100 valve stems for around $15 dollars. All the tire shops I’ve worked for had thousands of valve stems stocked up. This is because they are so cheap but such a crucial part to selling tires.
Some shops charge you a buck or two for the valve stems. Other shops do not charge anything, which may lead to the confusion of whether or not tires come with valve stems.
It’s almost every shop's policy that new tires come with new valve stems, so when you purchase new tires, you can expect to get new valve stems (with new valve caps) inside your new tires.
Tires, wheels, and valve stems all come sold separately and are assembled at the shop. The bare wheel comes first. Then the valve stem is placed into the wheel. The tire is then mounted onto the wheel. Once the tire is placed onto the wheel, air is put into the tire through the valve stem and inflated.
The valve stem is how air is added and subtracted, so without it, there would be no way to add air, and there would be no way for air to be kept inside the tire. The valve stem is the tiny part of the tire that all the air rests on, so it’s a crucial part of the tire that without, would cause the tire to not work.
What Can Happen If A Valve Stem Goes Bad?
Lots of times, valve stems ‘go bad’, meaning they start to fail. They can start to fail in numerous ways. One common way for valve stems to fail is for the Shrader valve to seize inside the valve stem.
Once seized, buildup can start to accumulate around the valve causing a gap between the stem and valve allowing air to leak out.
In this case, a slow leak will happen. Usually around 1-2psi a day until you walk out to your car and realize your tire has gone flat.
As a tire tech, this is usually the first thing I checked when a slow leak came into the shop. To test if the valve stem is seized at home, you can take some soapy water, and put it in a spray bottle.
Take the cap off the valve stem, and spray the soapy water directly into the valve stem. If bubbles start to appear, air is leaking from your valve stem and needs to be replaced.
Another common issue with valve stems is that they can get trapped between the rim and tire and a chunk of the valve stem can get cut off.
When this happens a leak is noticeable almost immediately. But it can also cause a slow leak as well. Either way, you can tell this happened by doing a visual inspection of the valve stem.
Look for any dings in the valve stem or chunks missing from the rubber of the valve stem. While these are just two common ways valve stems can go bad, the one way to check them for leaks is using soapy water.
So just spray some soapy water onto the valve stem, and check to see if the water has started bubbling up. If so, the valve stem is leaking and it’s time to replace the valve stem.
Valve Stems With TPMS
TPMS stands for Tire Pressure Monitoring System. What TPMS is, is an electronic gadget that sits inside your tires on your valve stem.
The job of the TPMS is to report to your vehicle’s computer the tire pressure of each tire. Your car has four TPMS monitors, one for each tire.
Sometimes, these TPMS monitors sit right on top of your valve stem so caution must be taken when dealing with a vehicle that has TPMS. For example, a mechanic has to do extra work to make sure they do not snap the TPMS when mounting and dismounting the tires.
TPMS valve stems can get costly, ranging from $60 to $120 per sensor. These electronic valve stems are vital for a modern car’s operation because they notify the driver quickly if any difference in air pressure is noticed in a tire by flashing a light on the vehicle dash.
No longer do you have to wait until your tire goes flat until you find out. That being said, valve stems with TPMS can be treated like normal valve stems by the driver.
The driver can add and remove air like normal, providing the tire with proper tire pressure.
You can even spray soapy water on a valve stem with a TPMS system to check for leaks without worry since they are waterproof.
The only issue lies with the mechanic who has to watch out when mounting and dismounting the tires.
Sometimes the tire scoop can snap a sensor, or the bead can crush one when the tire is being dismounted.
If you are truly curious, ask your tire tech to show you how they take precautions for the TPMS sensors when they deal with your TPMS sensor tires.
Some shops charge extra to mount and dismount tires with TPMS valve stems because of the extra work that needs to be done, so ask a mechanic to show you what I’m saying and see where your money is getting spent.
About The Author
Christopher Sparks
Christopher Sparks has been servicing vehicles since 2012. After completing the automotive studies program at Camden County College, he was awarded an Associates's Degree in Applied Science. His first job was a lube-tech at Jiffy Lube, and is currently an independent B-Technician servicing vehicles for the United States Postal Service. Christopher is ASE certified and loves rebuilding engines.
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