anyone know of such a product?
3M make a rubber masking tape that is meant to be very good, have a look for it at there online shop.
How about something like this -
http://www.mocap.co.uk/silicone-tape.html
protect against what? leaning it up against stuff or stone/rock strikes from front wheel? I'd be interested in something light clean and simple for the latter. (I know you can zip tie a bit of old tyre to your downtube but no thanks)
Protecting the down tube/bb sheel against rock impacts.
Zip-tie some mousemat.
I have done this with a hard-skinned neoprene mousemat and it just works.
PaulD
Have used the black foam base from a mouse mat held on with double sided 'carpet' tape. It has stayed on for a whole year and deffinately stopes damage from rock strikes to the downtube.