Lori....I think any possible negatives are worth the benefits of slime.....Offroad....

You know I'm a recent convert to slime but it really works....I run way too fast for my tires usually, never mind too fast for slime and I've only noticed one possible down side....My valve stems tend to seal up from the inside....Maybe it's the centrifical force being a lot greater at high speed forcing the slime up into the valve stem, I don't know....It's a pain sometimes but a lot better than a flat tire....Last weekend we accumulated over 4,000 total bike miles and only had one flat that would have not happened if irondawg had not forgotten to slime his rear tire.....Put it in and get riding....

On a related note...Bib Mouse inserts were not recommended for anything in excess of 75 mph but we ran one for almost a 1000 miles, sometimes over 100 mph without a failure in the '89 baja 1000....

Sometimes you have to do your own product testing....

Be sure to follow the instructions on the container.

Steve