A suspension that can move freely without binding is a happy suspension, and having a happy suspension means that you’re getting the most power transferred to the racing surface possible. To help a suspension move as it’s designed you need rod ends that have fully functional bearings and these bearings utilize a PTFE liner. To learn more about what a PTFE liner is and how to make sure it’s working properly, we spoke with John McCrory from the Aurora Bearing Company.
The metal race inside a rod end needs some type of lubrication to prevent metal-on-metal friction — that’s where the PTFE liner comes in. A PTFE liner is made of a Teflon-like material (“Teflon” is a DuPont trademark) that covers the area between the bearing and the rod end itself. This makes the PTFE liner a form of dry lubrication that doesn’t require much, if any, maintenance to keep the bearing moving freely inside the rod end. The liner is a composite that’s made of the PTFE material and fabric that uses the PTFE as a lubricant — the fabric provides the compressive strength for the bearing.
A PTFE liner is very durable, and that’s why it’s such a good choice to be used for suspension parts, as they’re exposed to the elements. McCroy provides some additional details about these liners.
“By their very nature, PTFE-lined bearings are very tolerant of dirt. The absence of clearance makes them ‘self-wiping’. The bearing surface remains dry when lubricated by the liner, therefore it does not attract dust and grit as a conventionally lubricated piece would. Once a clearance develops, then it’s possible for the unit to ingest dirt between the ball and liner. At this point, however, the bearing will probably need to be replaced anyway. As far as liquid contaminants, strong acids such as nitric and sulfuric must be avoided, as should strong alkaline fluids, as well. Most organic compounds and solvents have little or no effect.”
The PTFE liner is what makes the bearing inside a rod end self-lubricating, so it doesn’t need traditional forms of lubrication. When you add an additional lubricant to a PTFE-lined bearing it can actually prevent the PTFE liner from doing its job. Things like oil, grease, or moisture/corrosion inhibitors will affect the performance of the PTFE liner in a negative way.
“When a lubricant is introduced, the lubricant film that develops between the ball and liner act as a barrier that impedes the burnishing action. The movement between the two surfaces can remove the exposed PTFE from the liner face, but the material will not adhere to or burnish on to the ball surface. Eventually, the wear surface of the liner may have all the exposed PTFE material removed. At this point, the coefficient of friction between the uncoated ball and the wear face of the liner will drastically increase. In certain instances, liner debris can combine with the lubricant to form a paste of materials that will accelerate liner wear,” McCroy explains.
So as you can see, a PTFE liner isn’t some fancy technical sales term that’s used to get a racer to buy something they don’t need. It’s important to make sure you read the instructions on how to maintain the PTFE lined bearings inside your suspension parts to keep them function as they should. To learn more about PTFE liners check out the Aurora Bearing website right here.