I have found that anti-puncture strips are often not wide enough to stop thorns from piercing bike tubes, as the strips are only useful in the middle of the tire. I started using Slime, a green liquid sealant, after talking to a bike-borne cop who had very good results. I now use the stuff in my mountain bike and wheelbarrow tires. Actually, I bought pre-Slimed bike tubes when I got new tires recently. No flats at all for six years, despite rough use. I will confess to having to pump up a few times, though. If the bike is left parked in one position in, say, the winter season, the Slime may run down to the bottom of the tire, thus unsealing some of the sealed holes. As such, you will have to pump the tires and ride a while to reseal everything after a month of non-use. In cold weather, Slime puddled at the bottom of a tire while parked will cause a markedly unbalanced tire for the first few miles. This is most noticeable on dual suspension mountain bikes like mine, but it doesn’t seem to affect the operation of the bike.

The last time I changed bike tubes,I found 29 thorn holes Slime had sealed! Slime works in both tubed and tubeless tires, but with a few more caveats: it adds weight to the wheels, which is a disadvantage in racing. For normal road or trail use, you won’t notice. Also, Schrader valves are what to use with Slime, as the skinny Presta ones clog too easily. Tubeless tires, which are already heavier, also require special rims or rim treatments to prevent leaks through the spoke holes. I’d appreciate lighter wheels and tires, but my present tubed setup is fine for my use. Tubeless tires are much better than tubed tires at resisting “snakebite” (tire damage from striking a sharp-edged bump or hole at high speeds). However, tubeless tires obviously can be punctured by thorns, etc. — Slime will dutifully seal such. I have heard Slime itself will not patch “snake-bite” damage, as it is too far up the sidewalls for Slime to be thick enough to work. As I do not race (especially downhill) at 74 years old, tubeless tires do not tempt me. Slime does not last forever either. After a few years, it isn’t as runny, and may not seal a thorn hole in time to prevent needing to pump.

Some people say a Slimed tire cannot be patched by the usual means. Don’t believe ’em. You just have to wipe off the Slime from the area before patching it in the usual way. They offer incarnations of Slime for cars and motorcycles, too. Personally, I would not use Slime in automobile tires, as the high temperatures and odd balance changes might prove obnoxious. It’d be expensive to find out I was wrong. Bottom line: if you cycle where there are thorns (we call them”goat-heads” or “concho burrs”), Slime will greatly reduce flats. I have had only one flat in the last 10,000 miles — from running over a broken bottle bottom. Slime couldn’t seal the 1.5-inch slit. Neither could my patch kit.

-- J. Baldwin 06/16/08