After decades of relying on it, I had to give up Tuffy as its new XL construction is - by necessity given its use in plus and fat tires - too lightweight. It had a zero percent (0%) success rate against nails. So I went to Slime which claims it can seal holes up to about 1/4", and this is an accurate claim by and large. Along the way I have used Stans and Orange Seal in tubeless tires with success, and tubed tires with occasional success (its as likely to seal the tire hole and let the tube keep blowing bubbles as it is to seal the tube). The water-thick formulation of the tubeless sealants means they are great for thorns, less so for the big jagged stuff.
And all the while, Slime is good for up to 2 years in the tube. Stans and OS for much less, even the OS Endurance version. When slime dries in a tube you may as well change out the tube for a new one. Stans dries into weird alien shapes (google "Stans boogers") and OS dries to a thin film which is not so bad. FlatOut never dries. Put it in and you are done.
I heard a lot of chatter about FlatOut but the label on the bottle says nothing about bicycles. So I called them up and got the product manager for the Sportsman Formula (the one people were using) on the phone, and spent quite a bit of time talking to him about the sealant and their tests on bicycles with it. They tested extensively with BackCou (sp?) ebikes in wilderness settings. Lots more. I talked to him about using it for a tubeless sealant and no one had tried it yet, but based on his comments I went for it and it is *splendid* as a tubeless sealant.
Its rated as good for holes up to 1/2". Based on a couple of catastrophes I have had (tubed: a jagged piece of metal. Tubeless: a strip of 6 roofing nails) the product has worked perfectly and I'll buy the 1/2" claim as a result.
A couple weeks ago I heard the telltale hiss of a puncture but by the time I got off the bike to check for an embedded nail or whatever, the permanent seal was done. Only a slightly moist spot on the tread remained. FlatOut dries as a hard nub in the inner tube hole, unlike slime that leaves a weepy and sometimes slightly leaking hole.
Slime was good. FlatOut is a leap over it in tubes. Tubeless, its a leap over both Stans and Orange Seal.
If there is a drawback to FlatOut it is that you are prescribed to use about double that of Slime. Use 8 oz of Slime in a fat tire (Slime recommends half that and its not enough). FlatOut says use 16 oz. For a 29x2.5, use about 6 oz. Scale down from there.
