A constant velocity (CV) boot is a protective cover, usually made of rubber, plastic, or a similar compound, that provides protection for the CV joint. The CV joints allow the front axle to manage the torque produced by the drive wheels. They are found in all front-wheel drive vehicles, and there is one CV boot behind each front wheel.

The interior of the CV boot is usually greased or lubricated to protect the CV joint while it's in motion. In most cases, the boot requires maintenance or replacement before the CV joints. This is because rubber and plastic compounds have a tendency to degrade with age, especially when exposed to heat. The CV boot may rip or tear as it degrades, which reduces its ability to protect the CV joint. A ripped or torn CV boot cannot retain its lubrication.

A damaged boot cannot protect the CV joint, and that can lead to a damaged CV joint. Sometimes it's difficult to determine how long a CV boot has been damaged, and therefore difficult to judge the extent of the damage to the car's CV joint. Replacing the boots can be expensive because they are difficult to access.

Although it is possible for backyard mechanics to replace a CV boot, the job usually is best left to professional mechanics. The task requires the vehicle to be safely lifted and supported, and also requires the front tires, as well as the wheel hubs and brake calipers, to be removed. An amateur attempting such a repair may accidentally inflict bodily harm upon himself, and may cause further damage to the vehicle.

Some mechanics recommend replacing the entire driveshaft when CV boot damage is discovered. This is because the cost for replacing the entire driveshaft is similar to replacing the CV boot due to the labor involved. Additionally, because it's hard to determine how much damage has occurred because of the faulty CV boots, one can assume the driveshaft will have to be replaced in the near future anyway.