Right now I commute with a 1 1/8" tire and a 1 1/4" tire- rear is kevlar belted.

In a few thousand miles of riding, I've had a couple punctures on the kevlar-belted tire, even with a tuffy tire-liner inside! With bikes that have fatter tires, I haven't had many flats despite the fact that I didn't use tire liners or kevlar-belted tires.

Now I sort of want to get fat mostly-slick tires that have a lot of rubber between the road and the casing, because the kevlar in the tire I have seems to stop fat things but sometimes not little tiny pieces of junk like fragments of staples. These things aren't even long enough to puncture a lot of bigi tires, but they sometimes go through my little tire, kevlar, tuffy liner, and tube included.

Of course, I once got a nail through my kevlar tire, but it's difficult to do something about that.

I went to www.notubes.com and their video is really impressive. But it doesn't tell you whether the sealant will hold if you ride the bike for a few days afterward. I'm sure they're right that you can use the sealant on tires with or without tubes. They don't say whether it works on 90psi tires as well as it works on 40psi tires. I had slime-filled tubes that would hold air fairly well (and slowly leak slime) for a day or two after a puncture, and then fail to hold air for more than a minute or two.

The other thing that concerns me about sealants is that notubes.com says that their sealant dries out after a while (faster in dryer weather) and gives no specifics at all regarding how long the sealant lasts in dry or wet climates. I wouldn't see much of a problem with sealant that dries out after 6 months, but it would get annoying and expensive to replace the sealant every month.