Originally Posted by
cyccommute
Of course you could use sealant, such as Slime, in tubes to get the same protection against flats. The sealant in the tubeless negates any weight savings of not using a tube as well.
As for no pinch flats, you can avoid that problem by keeping your tires inflated so that the tire doesn't bottom out on impacts. And, while you may get a bit better traction at lower pressures, the possibility of burping a tubeless tire and the possibility of damaging a rim when the tire does bottom out increases significantly.
And there's the maintenance issue of the sealant that you failed to mention. Sealants have traditionally needed to be "refreshed" every 6 months or so because they "dry out". My question on this issue has always been, how? If the tire isn't constantly leaking air somewhere...not normal diffusion but a serious leak...how does a liquid get out of the rubber container? While rubber is permeable to gases, it's not permeable to liquids...think old tires that serve as perfect mosquito breeding grounds. Where does it "dry" to?
The answer lies in the sealant itself. It contains propylene glycol (or other glycols) which dissolve into the rubber. This problem used to be manifest by blistering of tires when used with early tubeless set ups. The rubber used is a bit better now but the glycols still dissolve into the rubber.
Propylene glycol isn't particularly volatile so it stays in the rubber. After the first 6 months when you refresh the sealant, the sealant is in the rubber...about 4 oz per tire...along with the new sealant. Your tires have gained 8 oz of weight in 6 months. Another 6 months, another 4 oz. And so on. There's a limit to how much glycol can dissolve into the tire but I have no idea what it is. Basically, any weight savings over a tubed tire...which is debatable because tubeless tires tend to be heavier...is quickly lost from carrying around the "lost" sealant in the rubber matrix of the tire.
Frankly, given the difficulty of mounting the tires, the need for constant maintenance of those difficult to mount tires, the possibility rim damage, the "loss" of sealant and attendant weight gain, plus the inability to repair a flat on the road, I have a very hard time seeing any "advantages".
Yikes, where to start. No pinch flats with tubeless. Bonus. Never burped a tire, ever. Great. Some tires do seep. So maybe 3-4 times a year, add some sealant. Through the valve, takes 5 minutes. It's not dissolving, it is evaporating. Lower rolling resistance. Nice. Lower psi, so awesome. Weighed a fat bike tube? Mine was one pound. Weigh a 29er tube, do you even own one? Not light. Mount the tires with a floor pump, no issues. Less maintenance than fixing a flat trail side. No flats, no need to fix. Some do carry a plug kit for bigger holes. See a thorn sticking out, pull it, spin the tire, fixed. Easy. Weight may be a wash, but I'm not one to weigh stuff. The real question is, how many miles do you have running a proper tubeless setup, with good tires and rims? Guessing NONE. Maybe once you have actually tried it you might have a different opinion. No one who has switched to tubeless has said, gee I wish I could go back to tubes. They rock for mt biking. And almost all of the say + $ 1,000 mt bikes sold in the last few years come tubeless ready. Hmmm. And with disc brakes. Yowzer.