If you have ever put used auto parts on your vehicle, you might have stood in front of two rusty car parts trying to remember which one you just purchased, because they both look rusty and worn out. Certain auto parts are absolutely fine to purchase used, and in some cases may be your only option. There are a variety of parts that are considered regular wear auto parts and should not typically be purchased used.
Struts and Strut Assembly do not get these auto parts used. Once you have a strut is separated from its assembly you can test that strut. You should be able to depress and extend that strut, all the while, feeling a uniform pressure. Being able to do this demonstrates a strut works without load, however being able to tell how long that strut is going to operate is mostly a guess. Buying a used complete strut assembly, on the other hand, is even more of a guessing game. A junk yard will have these things removed from various vehicles, and they are often of unknown or fictitious mileage; and of course you aren’t able to test the strut when the spring has not been removed from the assembly.
Brake Rotors and Brake Pads are probably the most common automobile wear car parts. They can usually be purchased cheap enough that it is simply not worth your time installing a used set. Each brake pad has worn grooves into each side of the rotor and after that brake pad to brake rotor seat has been made, you don’t want to change any relative positions. Since brake rotors will rust almost instantly after they have sat for any period of time, it is very rare that anyone would be interested in installing these brake components used.
Hub Bearings and Hub Assemblies are another thing that is completely pointless to purchase used. You are either spending your own time installing the hub bearing, or paying a mechanic to install the hub bearing that may fail at any time. Time and mileage are both contributing factors to the failure of a hub bearing. It is difficult to tell if a hub bearing is OK before installing it, and virtually impossible to tell how long it will last. The longer the hub bearing has sat the more chances there are for that hub assembly to fail.