I just added “Goop” to my TT1200 tyres, I have used its close relative “Slime” in my mountain bike tyres for years, once I removed a tyre to find 6 green dots on the inner tube where I’d had punctures I wasn’t even aware of. So put it in earlier and I’m out for a ride now, I can vouch that it doesn’t affect wheel balance having just ridden at speeds up to 70 with no issues, whether it’ll stop punctures remains to be seen of course, I’ll probably get my rims adapted to tubeless in the future but hopefully this will work until then, here’s one of Del Boys videos on the subject. NB I put my bike on paddock stands when I did mine, didn’t want the rims bearing down on the inner tubes. PS I also cleared the goop out of the valve bodies with a cotton bud before refitting the valves, not sure this was necessary but only took a sec. Note, his comment on using virtually no force when tightening the valves is correct, finger tip torque only!.
Slime and similar stop-leak products work well enough in innertubes, but I would avoid using it in tubeless tires; the mess is unbelievable, and difficult to clean-up. As an alternative in both varieties of tires I've found that the copper-based radiator stop-leak diluted by 50% with water works really well, with a fraction of the mess and easier to clean. Simply remove the valve stem core, and inject about half of a turkey marinating syringe worth of the mixture into the tube or tire, reinstall the stem core, air-up and drive normally. I've used this in the tubeless tires on my quad, and it defeats even the dreaded Goat's Head thorns that are prevalent in the American desert southwest (Goat's Heads will penetrate Kevlar belted tires).
