I’m new to road tubeless and I need advice from someone experienced. The internet is stuffed with unhelpful polarized opinions and even my LBS can’t give me a decisive answer. Your help would be appreciated! Here it goes :
I managed to get a sub-millimeter puncture on the middle of sidewall of a 6 weeks old Zipp Tangente RT28 tubeless tire mounted on the new Zipp 303 Firecrest MY21 tubeless rims, after rolling on a 1 inch diameter rock with sharp edges. I’m using Stan’s NO TUBES regular latex-based scellant.
Upon impact, the tire completely deflated and the scellant did not provide protection. It’s unclear to me if the tire “burped” or if the air escaped from the puncture, but it was fast. I stopped, removed the wheel, held it horizontally with the puncture facing down, and shooke it slowly sideways so the scellant could do its job on the sidewall. I finally managed to reinflate the wheel (I was keeping it vertical when inflating) to an acceptable pressure using a 6 inch-long “ultra-mini” pump (I avoided using CO2 not to wreck the scellant), and rode 500 meters before having to stop again. I repeated the process, and this time I was able to make it back home (about 8 km).
The tire had deflated quite a bit upon arrival. Did the same process again, but this time with a track pump. Pressure held well, so I decided to give it hell to make sure it was safe by hopping with the bike 5-6 times. The scellant plug popped out. Did the process again, hopped about 10 times with the bike. This time, the puncture remained sealed and pressure held well.
I then went for a 120 km ride with the same tire. I left with 57 PSI and came back with 54 PSI. Zipp recommends 56 PSI for the front wheel for my weight.
But now I’m nervous : I have a 200 km gran fondo coming up in a week, and I’m scared to ride the same tire.
When reading about puncture protection provided by the tubeless system, my story does not correlate. I must have been doing something wrong. I thought about it a lot, and read everything I could find on the subject, and came up with a few hypothesis of what went wrong :
Hypothesis #1: Scellant could not coagulate due to lack of pressure drop
This is my main hypothesis. My mini-pump is ridiculously small and provides a microscopic volume of air for each stroke. I thought the mini-pump would do the job just fine since these tires have to be inflated at very low pressure so I could minimize what I carry. Is it possible that the scellant could not coagulate properly because air mainly escaped from the bead and did not produce any pressure drop where the puncture was? Additionally, when trying to re-inflate the tire, the ridiculously small pump I was using, although capable of bringing the pressure up in the tire, could not create the pressure drop & evaporation required for coagulation?
Hypothesis #2: Since the puncture is in the sidewall, I should have inflated the wheel while keeping it horizontally?
Not much else to comment on that, other than using the track pump seemed to have been more efficient at making the scellant do its job. However, this was also after spinning the wheel for 8 km. In any case, I’m looking for a method to get me out of the woods when I’m 4 hours away from my hotel room / home.
Is it safe now? Can I ride 200 km on the same tire or should the tire be retired?
Now that the sidewall puncture is plugged, and that the tire is holding its air, is it safe for the grand fondo? I do have a backup tire I could install, but then I’ll have no spare and I would be replacing an almost brand new tire that now seems to perform properly. I’ve read conflicting information about retiring tubeless tires once the sidewall is damaged. I’m not sure what to do anymore.
P.S. Yes, I do carry a tube and CO2 but that’s not what I want to discuss here.
Your input would be greatly appreciated!