Oil Seal Chain Structure
The rotating components of an oil seal chain consist of pins, bushings, rollers, and oil seals. Lubricating grease is present between the pins and bushings, and the oil seal prevents grease loss.
Replacement Criteria
Pull the chain at the chainring by hand. When a noticeable crescent-shaped gap appears between the chain and chainring, it's time to replace the chain. At this stage, the pins and bushings have worn significantly, causing chain elongation (due to pin-bushing wear, not like rubber stretching). Continued use risks the chain slipping off the cogs during compression, potentially causing accidents. Naturally, a chain that has become knotted should also be replaced.
Maintenance
Personally, I believe chains require no cleaning agents whatsoever. Online cleaners marketed for sealed chains-whether volatile oil-based or water-based-are, in my view, a waste of money. Reason: Volatile oil cleaners, like WD-40, effectively dissolve grease and can easily seep into seals, causing internal lubricant loss-especially when seals are worn. Water-based cleaners pose the same risk. Therefore, I believe proper chain maintenance only requires wiping the chain clean with a cloth (or spraying some gear oil and then wiping it clean), followed by applying chain lube, gear oil, or chain wax. Of course, after riding in the rain, promptly rinse off any sand particles from the chain before reapplying lubrication.
The purpose of lubrication is to coat the seal area, reducing wear between the seal and chain to extend seal life, while also minimizing friction between the chain and chainring.
