Originally Posted by
staehpj1
My experience with tubeless and with slime tubes is with different disciplines of biking (tubeless on mountain bike only; slime tubes with touring bike only), so to some extent I may be comparing apples and oranges, but I think there are differences. First the sealant itself is different. Second there is a difference in that there is movement of the tube against the tire. I have been told that movement makes the sealant less able to stay sealed. I can't say with any certainty that is the case, but I tend to believe it, at least with the still thorn in.
I would agree that the sealant is different. Slime doesn't need to be replenished while most of the tubeless sealants I've heard about have to be refreshed and/or replaced every few months (3 to 6 seems to be the interval). Stan's, for example, tends to dry out over that time frame. The real question you have to ask is where does it go? The bicycle tire is a sealed system that is (mostly) impervious to liquids. If you were to fill your bike tires with water, you would still have water in them 6 months later. That's what makes tires such a good home for mosquitoes.
It took me a while to figure out where that liquid was going and it all has to do with the solvent used in tubeless tire sealants. Slime uses glycerol as the solvent while the tubeless sealants are mostly propylene glycol. The propylene glycol has a fair amount of solubility in the rubber of the tire and penetrates it. However, propylene glycol doesn't have much in the way of vapor pressure so any that ends up in the rubber stays there. Some will be ablated away with the tire rubber but, for the most part, it dissolves into the tire and stays there.
Glycerol doesn't do that so it doesn't need the constant refreshing.
Originally Posted by
staehpj1
Weight of the sealant for my tubeless setup is 2 ounces per tire. A standard weight tube in that size is typically <8 ounces. The tires are pretty light. I don't have the weight handy, but the Stans Ravens that I use are among the lighter tires I have used in that size. They are the lightest MTB wheel/trie setup I have owned so I don't feel like there is much of a weight penalty.
I think you are underestimating the amount of sealant in the tires and slightly overestimating the weight of a standard tube. According to the Stan's tire installation instructions, a tire should have 1.5 to 2
cups of sealant per tire. That's 12 to 16 oz of fluid per wheel.
There's also the issue of the sealant dissolving into the tire. If you put in 12 to 16 oz of liquid and 90% of it goes into the tire and stays there and then you add another 12 to 16 oz of sealant, that adds up to a couple of pounds of weight after only a few months. And, as I'm not sure how much propylene glycol the tire can hold before it starts moving out of the tire due to rubber ablation, I can't say how much weight is added the next time you have to refresh the sealant.
The whole "refreshing sealant" thing is probably what bothers me about tubeless the most. Personally, I don't what the headache of having to do that on a regular basis.
Originally Posted by
staehpj1
The Stan's No Tubes Ravens on Stan's wheels mounted easily and seated with a frame pump. When I had a spoke break (a stick snapped it off with the stub flush in the nipple), the tire came off and went back on easily enough. I understand that may not be typical of all or maybe even most tubeless setups.
I don't have tubeless and probably never will go that route. But I have been involved in trying to mount them and I see the paid mechanics at my local co-op when one comes in. Nobody really want to mess with them. It's kind of a toss up between which is more onerous: brake bleeds or tubeless install. I'd almost say they'd rather do a brake bleed and nobody wants to do that one.
The tire that give us all so much trouble was one that had an o-ring kind of bead on it. The "o-ring" was pressed into a channel around the rim and it was next to impossible to break free. We ended up having to use Park Tool's long metal tire levers and had to use them the entire way around the tire on both sides to pry the o-ring out. It was no easier to get the tire to seat either. It was one of the more challenging things I've ever been asked to do and that is saying a lot considering what kinds of problems we see every day at the co-op.
At the same time we had the guy's girl friend who had managed to burp the tire off her road bike rim by running it at 15 psi
. That one was a bugger to get seated as well. We emptied the compressor a couple of times because we just couldn't get the tire bead seated. Sprayed sealant all over as well.
Basically, I wouldn't want either of those hassles in the middle of no where.