Flat tyres on adv bikes?

[Transalper]

stretching a 17 in ch tube to a 21 inch rim may not work,.......

I carry one spare 19 inch tube to do my 17 inch rear wheel or 21 front on the DR650.

[NordieBoy]

I like "True Blue Tyre Goo".
Worked well the only time I've needed it to.

The other times it was sitting on the bench at home when I needed it

Only works if the hole is in the outside circumference (tread area).

[Woodman]

For the lube I use little sample packs of handcleaner.