interesting tiddy on wd, and sums up better than i could why i like using it...
chain cleaning, waxing and wd-40
is wd-40 safe to use on your chain?
Yes, all motorcycle chains currently being manufactured use buna-n (nitrile) rubber for their o-rings and x-rings, and all these manufacturers recommend kerosene as a cleaner.
Here's the formulation of wd-40:
80% stoddard solvent (that is similar to kerosene)
20% light lubricating oil, and a bit of fragrance.
Here's the compatibility of stoddard solvent with rubbers and plastics:
Good compatibility (ok for both static and dynamic seals)
mixed compatibility (ok for static seals, but not for dynamic seals)
fair compatibility (ok for some static seals)
consequently, wd-40 is safe and effective as a chain cleaner and corrosion inhibitor.
if you clean with a soft brush and wd-40, and plan to follow-up with a chain lube, you can reduce chain lube sling-off if you first remove the oil residue that wd-40 leaves. This residue seems to prevent some chain lube formulations from sticking well to the chain.
Should i also use a chain lube afterwards?
The answer depends on whether external chain lubrication is beneficial for a chain with internal grease sealed with o-rings, and perhaps how often you clean your chain.
One school-of-thought believes that no additional lubrication is needed. The other believes that the sprocket and chain surfaces that do not have permanent grease also need to be lubricated.
The chain manufacturers tell us that also lubricating the chain and sprocket surfaces will extend the life of these components. But a chain lube will sling-off unless designed to stick to the chain, so it needs to stay tacky. Consequently, it will also attract grit and road debris that, in turn, will accelerate wear faster than if you just have a clean unlubricated chain. Chain lube will also reduce power losses due to friction and shed water that leads to rust (and wear). If you live in a wet climate, you should probably use chain lube to prevent rust.
A chain newly-cleaned with wd-40 will have a coat of light oil that will effectively displace water and reduce surface corrosion of the links. It's a low viscosity oil so any excess will sling off easily, but will attract very little grit - much less that any chain lube - and it will have the same rolling friction as a number of chain lubes on the market.
Wd-40, used as a one-step cleaner and lubricant is sufficient. Because it is a light oil, some fling-off will occur, so any excess should be wiped-off. Used regularly, it provides good corrosion protection, low (but not the lowest) rolling resistance, and attracts less road grit than waxy chain lubes. So your chain stays very clean.
If you aren't inclined to clean and lube your chain regularly, or often ride in wet conditions that promote corrosion, there are chain lubes on the market that are designed to stick to your chain to resist fling-off and provide longer-lasting corrosion protection. Some remain tacky and attract grit, some stay slippery to the touch. All of them need to cleaned off and renewed at some point.
If you’ve decided to use chain lube after cleaning your chain, then it’s best to use straight kerosene as your cleaner because the light oil that wd-40 contains will make it difficult for the chain lube to stay attached without flinging-off.