Silicone spray any good on cranks

If you are talking about silicone spray, sure, just don't rely on it as any kind of useful lubricant.

If you are actually talking about wd40 (the water repellent/ "lubricant" spray), don't get it in the bottom bracket bearings or on to the chain. Ideally, I wouldn't get it on any part of the chainrings that will make contact with the chain. It is a more of a solvent than a lubricant and will dissolve and remove your chain oil or your BB grease.

+1. WD-40 is a great solvent but does a poor job as a lasting lubricant.

Quoted post said:

Originally Posted by cyclejohn [IMG]/img/forum/go_quote.gif[/IMG]

Is silicone spray with wd 40 safe to use on road bike cranks?

You need to be more specific as to where exactly you intend to apply it.

Is it for use as a grease in BB bearings? Is it for use on chainring bolts? Or is it intended for the chain?

WD40 is not suitable in ANY of these cases. Silicone spray can be useful as an assembly grease where carbon fibre is involved (like where chainrings contact carbon crank spiders), but is usually not suitable for metal/metal contacts or for bearings or chains.