So recently I bought a pair of Bontrager Latex inner tubs to use on my clincher wheelset. I was considering using this wheelset for IM and HIM races this year instead of my sewups which I normally use for racing. Last year I flatted on a sewup (Zipp 808 tubs) while doing IMLP and the tubular tire change cost me a lot of time. So I figure that if I could use Latex inner tubes for my R4 Bontrager clincher tires (Vittoria uses Latex for its sewups) then maybe the ride will be as good as my sewups. However, what I find annoying (which everybody does) about the latex inner tubes is how fast it losses air. I have had to pump my wheels virtually every day or two because (as we all know) latex tubes loose more air being more porous than butyl. Aside from that annoyance, I think latex tubes ride better than butyl. But I digress…
As part of my test, I also wanted to try out the Stans no tubes sealant on my clincher inner tubes first before using them on my tubular (sewup) wheels. So the experiment was on on two fronts:
- The latex flat resistance and ride quality; and
- The Stans flat sealing technology.
I poured some Stans sealant into my latex inner tubes and installed them on my clincher wheels. Pouring the Stans sealant was fairly easy since I only had to remove the tube valve core. I didn’t pour in a lot of sealant and I estimate only about 3 to 4 tablespoons per tube? Or thereabouts. What made this test complicated is that I used the latex tubes on my Bontrager Aeolus 9.5 wheelset - which has a carbon fairing about 3 inches high. Therefore I had to use a valve extender - and effectively had to keep the valve open on the tube. I’ve done this before on butyl tubes and sewups (keeping the valve open with extensions) and it didn’t give me any problems before. To pump air, one simply had to attach the pump on the extension valve head and pump away. No need to close valve since it is permanently open inside the carbon fairing. To remove air, I would poke the extender with a spoke (effectively pushing the valve in) which would release air. Been doing this for years and never had a problem with “open-valve-on-valve-extenders” on both my clincher and tubular wheelsets.
back to the test…
So the first thing I noticed is that the wheelset wasn’t losing air as fast as it used to. Whereas before I would pump my wheels every day before using. I only had to pump it every three days as there was clearly less air leaking out. Perhaps because of the Stans sealant? That would be the only logical reason for the less leaks. So I was fairly glad with that. I still had to pump it more than I would pump my butyl tubed- wheels but much less than I used to. I also noticed that you don’t really hear the Stans sealant inside your wheel and there is no “rolling imbalance”. I had the impression that with the liquid squishing around inside that the rider could actually hear it.
So after using the wheels for a couple of weeks, I noticed that the ride got a little harsher than what it used to feel like. I pump my wheels to 115 – 120 psi only so it doesn’t ride too hard but I noticed that it felt like it was pumped up to 150 psi. Perhaps the Stans sealant was hardening inside the walls of the latex tube and making the walls thicker?
Finally one day I noticed that I could not pump air into my rear wheel. The front wheel was ok and it took in air from the pump but the rear wheel was totally clogged. Recall above I mentioned two things: (1) I still had to pump air into the wheels periodically because there was still some leakage being latex (albeit less due to the Stans); and (2) My valve core is permanently in the “open” position as I use a valve extender for my high profile rim.
No matter how hard I pumped, the tire would not accept air! So to test the valve if it was still open inside the extender, I poked it with a spoke (as I explained above). Nothing happened. I tried doing this test on the front wheel (which still accepted air) and I could hear a hiss. The rear wheel - nada! So effectively, the Stans sealant “sealed” shut my open valve inside the extender.
Hhhhmmmm…. I called Stans and described the issue to the customer rep. He explained that normally, the Stans sealant would stay in its liquid form inside the wheel for 6-months to a year – for as long as the tube / tire remains sealed. Meaning, without introducing “new air” into the tube / tire, the sealant stays fresh. Otherwise, the sealant will slowly start forming a spongelike foam and eventually harden. But this would only happen after a prolonged period of a few months.
So what happened to my wheel? It could be due to any of the following issues:
-
Pumping the wheel and constantly having to add “new air” into the inner tube (being latex) effectively exposed the Stans sealant to new air and cause it to foam and harden much earlier than it normally did. -
The inner walls of the latex tube is now thicker due to the sealant or due to a harder foamed core – resulting in a harsher ride. -
The sealant effectively sealed the valve and despite its “open position” inside the extender – the pump couldn’t dislodge the seal.
So what to do with the wheel? The wheel is fine and usable as long as it stays hard. The problem will occur if it loses air slowly (being latex or for whatever reason) then I may have to try to destroy the valve by pulling out the extender and hoping the air leaks out of the open valve. If it does not then I may have to wait for the entire wheel to get soft and slowly pry out the tire from the hardened inner tube.
Would I do this again? Yes, but only under a couple of conditions:
-
Use butyl inner tubes -
No valve extenders or open valves -
Not on high profile carbon rims -
Not on tubulars / sewups unless you are willing to condemn the tire for good if the Stans hardens inside.
I will provide an update with pictures of the problem wheel when I get the chance in the near future. As of now, it still rides ok…
.