Sealing is Believing!
We live in a word dominated by air, dirt and water. When it comes to sealing components on a bicycle, those last two are about all that matters.
A bicycle is a simple mechanical device that consists of numerous moving parts that are all expected to provide a reasonable level of service.
Friction dominates the moving mechanism’s world and mechanical designers strive to reduce friction and increase performance. It is reduced in a number of ways:
- By utilizing rolling element bearings (as opposed to bushings)
- By utilizing lubricants to separate surfaces with relative motion in contact
- By utilizing materials and surface finishes that have a lower coefficient of friction relative to each other.
- Sometimes a combination of all 3.
If we look at a typical mountain bike suspension fork, nothing specific, the basics are all the same, we have:
- Upper stanchion tube/crown/steerer assembly
- Bushings (coated in some sort of friction reducing material)
- Spring (air or coil)
This is one of the harshest applications for sealing on a mountain bike. Since in most applications, the sealing surface is rotating (as with a bearing) there is not a wedging action of dirt and particles that can compromise the delicate sealing lip and contaminate the lubrication inside.
The newest releases of FOX forks utilize a fox “low friction seal” in my experience these seals are less effective than the older seal. One way they have reduced the sliding friction at the sealing interface is to lower the seal contact pressure. This, in reality, while reducing friction, also reduces the effective sealing pressure of the seal, making them more susceptible to contamination and failure. Fox states specifically that there is no reduction in sealing performance, but through real west coast riding, I have seen an increase of seal failures since the introduction of this technology. I am not necessarily knocking the low friction seals, because they really do seem to reduce the amount of fork friction, what I am suggesting is that forks with these seals need more frequent attention to seal and lower lubrication changes then they had with the older “high” friction seals.
There is always a tradeoff in performance, weight and cost and reliability when it comes to mechanical components.
The biggest enemy of proper lubrication is ingress of dirt and water. Dirt causes abrasive wear on the two sliding surfaces and water causes a breakdown in the lubricant (since is emulsifies, or displaces) and then the surfaces contact and wear each other. Just in case you did not know, that is what lubrication does, it creates a microscopically thin film and separates the two surfaces.
Marketing dominates the cycling world, if you are able to sift through all of the marketing and subjective BS and get to the nuts and bolts, then you my friend are the exception.
Because of my background and education, I take a keen interest when gear does not work properly and or fails (and an even keener interest when it does work properly!)