[n1acguy]

303 is a rubber and vinyl protectant.
If the bikes aren't too dirty with grit, I dry wash with Pledge.

[Arizoni]

I don't have first hand knowledge of S100 but I do with 303.

It is called 303 AEROSPACE PROTECTANT (which is a protected trade mark complete with what looks like a mis-spelled word).

It is a sun block that says on the label "SPF 40" For Your Stuff.
It is made to protect plastics, vinyl, Naugahyde etc.

It is about the best stuff I've ever found for this, beating ALL of the other so called protections by a wide margin.
It doesn't come cheap and I've only been able to find it in my area at Boat Shops where it is sold to protect seats, canvas and similar stuff that is exposed to rain, surf and sunlight.
It is sprayed on and wiped off leaving no real trace except the surface looks newer.