If the nice pewter head tube badge falls off your expensive hand made bike, what’s the best gunk with which to stick it more permanently back on?

Ta.

Double sided 3M stuff with a mm or so of thickness to it perhaps?

Like you get for GoPro helmet mounts.

yup, that ^.

Araldite.

3M VHB (very high bond)tape in 1mm or so.

It’s a fiddle to trim to the right size and peel backing off.

Araldite is a good suggestion but you’d need to take care it doesn’t drip.

Copydex.

Fixes almost everything.

weetabix

Car number plate tape?

Copydex tempting; Weetabix not far from the porridge I was planning to use; don’t like the idea of putting araldite on my gorgeous paint; 3M seems the obvious route and probably what was under there to start with. (And I don’t trust car number plate tape on my car number plates, let alone my much more important head tube badge.)

Thanks.

Shurely get in touch with the maker, if it was expensive then he’ll be keen to get his badge stuck back on ?

You could go to Halfords and get number plate fixing tape. It’s not overly sticky at first but sort of develops and ends up incredibly tenacious and also waterproof.

And I don’t trust car number plate tape on my car number plates

I do, having used the same number plate on three caravans – removing the plate by hand was very difficult indeed, it was never falling off on its own in a million years. I cleaned and de-greased first of course. It’s foam backed (or centred?) so works with surface irregularities.

Genuine 3M double sided foamy stuff, not ebay knock off crap and not Araldite, it’s not weatherproof so it will eventually come away and you’ll lose the badge.

Copydex

Did anyone else paint this all over their hands in school, just for the fun of peeling it off?

+1 for the 3M tape.

My number plates aren’t falling off, they live outside 24/7, get all the weather, and get a fair breeze when “pressing on”.

A couple of well soaked cornflakes. Takes a while to dry, but the strongest adhesive currently known to man.

Gorilla tape!

https://www.amazon.co.uk/Gorilla-Glue-3044101-Heavy-Duty-Mounting/dp/B01FMXKIOM/ref=sr_1_5?crid=P9T8WRLHUA2U&keywords=3m+tape+double+sided&qid=1580914688&sprefix=3m+tape%2Caps%2C143&sr=8-5

3M VHB tape is what good number plate tape is, it’s works well provided you clean and degrease everything but that clear gorilla tape stuff in the link above is amazing, highly recommended – again clean and degrease everything with isopropol or brake cleaner.