RubeRad

Good info, thx. Just pre-ordered this bike which advertises "tubeless-ready". So in theory (assuming 'tubeless-ready' includes good rim tape) if I wanted to go tubless I would just get some sealant and replace the tubes with valves, and try to inflate/seat/seal and be good to go?

Leebo

The sealant dries out. Weeps through the side walls, the bead seat and fixing small holes. The main advantage for tubeless in mt biking is the ability to run lower pressure and the elimination of pinch flats.( No tubes). For my riding area, no thorn flats either. The sealant does not dry out in a sealed plastic bottle, so the tires have to be porous somewhere.

noglider 

I suspect tubeless tires will remain a specialty item in the way tubular tires are. Some will be willing to go through the extra expense and labor, in pursuit of a superior ride. But it's hard to justify those costs for everyday riding.

cyccommute 

"Curing" is different for "drying". "Curing" involves polymerization which is the making of larger molecules from smaller molecules. Examples are urethane glues and finishes, paint, plastics, or the formation of Stan's corals, etc. These can all be performed in the presence of a solvent, although some polymerizations need the removal of the solvent to cure entirely. Removal of the solvent is "drying" and doesn't necessarily lead to an increase in molecular weight of the material left behind. Examples of "drying" are removal of water from a salt solution, actual "drying" of the water in paint, removing solvent from a chain, etc.

Yes, paint can "cure" or polymerize in a sealed container. But, in my experience, this occurs with a water layer still on top of the paint unless the can really isn't sealed. Drying out the sealant in a tire requires the removal of the liquid and the mechanism for that removal is what I question. Where does it go and how does it pass through a water impermeable barrier?


Let's start with the tubeless tires. Without sealant, a tubeless tire would be just as susceptible to flats as any other tire. The air tight layer isn't going to provide any kind of puncture protection so I doubt you'll see too many people running them without sealant. But even then, the sealant has to be refreshed.

Tubeless-ready tires may leak on the initial installation but once the minor leaks are filled, they should stop leaking air and, more importantly, retain the liquid of the sealant. If the sidewall is weeping sealant, the tire will be losing air as well. If the rate is higher than that of a standard clincher with a tube, what advantage does a tubeless-ready tire have over a clincher/tube system? Add to the need to be constantly refreshing the sealant and the tubeless-ready system is starting to sound like more of a hassle for no real benefit.

Similarly to the tubeless-ready tires, a regular clincher should fill the voids in the tire and eventually stop leaking sealant. But, again, the sealant has to be refreshed on a regular basis.

At the normal charge of 2 oz (56g) of sealant and the suggested refresh interval of every 3 months, that's a lot of mico-punctures. I would suspect that a huge puncture would require a few miligrams at most of sealant to seal the hole. If you assume 10 mg per goathead puncture (which is a large hole), that should be enough sealant for 5600 punctures before you'd run out of liquid. I can get a lot of punctures here in goathead infested Colorado but I don't think my lifetime number is 5600.

Bottom line: I'm not buying the micro-puncture idea.

Bicycle tires...any tire really... diffuse gases. That's why they need inflation on a regular basis. Liquids are very different from gases. The molecules are too densely packed to diffuse through something like the rubber of a tire at any appreciable rate. Water in a much thinner rubber container like a water balloon wouldn't diffuse through at a rate that could be considered anything but geologic. Having to replace a relatively large volume of sealant every 3 months is a very fast rate for a seal (to liquids) system.

The big question is "if sealant weeps into the tire?" It shouldn't pass through the rubber at all unless there is so thing else going on. Given that I seen a few blistered tires and that the sealant contains propylene glycol, I do suspect that the sealant is getting out of the tire by actually dissolving through the rubber and/or through the cords of the casing. I wouldn't look on that as a good thing. If the glycol is dissolving into the rubber, the rubber is swelling which can lead to various problems.

I suspect that I have my answer on where the liquid goes. Frankly, I'm not planning on switching over to tubeless on anything in the near future because the more I look at the system, the more of a maintenance headache it appears to be. Especially since we haven't even discussed fixing a flatted tubeless in the field. I'll pass, thanks.

cyccommute 

Personally, I've never seen the need to run super low pressures on a mountain bike. Sure it may help in climbing but even without pinch flats, low pressures put your wheels at more risk of damage when you hit something on a downhill. Yes, you can repressurize your tires for the downhills but my mountain bike rides are seldom uphill and then downhill. I'm going up and down all the time. I've not experienced too many pinch flats either because I'm not trying to run my tires at low pressure.

Road tubeless tires have a lower pressure rating than "normal" tires as well. That lower pressure might be good for smooth roads but for city streets with potholes, a narrow tire with low pressure sounds like a recipe for rim damage as well. A pinch flat is relatively easy to fix and easy to avoid. A damage rim is a far more expensive proposition.

As for the porosity of the tires, see above. Tires may be slightly porous to air but they are nonpermeable to water. If they are permeable to propylene glycol, that's not necessarily a good thing.