Originally Posted by
Leebo
99% less flats. I'll speak from a mt bikers perspective. No tube to pinch flat. They use a sealant that when you roll over a thorn or other small pointy object, the sealant seals the holes. Also the ability to run much lower pressure is great for mt biking. No weight of the tube, less rolling resistance. Better traction and grip( for mt bibking)
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".