I suspect many people who have any experience with road tubeless have concluded that term is an oxymoron, like postal service or jumbo shrimp, and I can’t blame them.
A few weeks back I had three flats over a five-day span on a road tubeless setup. For various reasons I opted to fix the flats rather than swap for clinchers and tubes. My reasons had more to do with my sense of professional responsibility than my convenience, though I did enough walking in a pair of gravel shoes my feet have some opinions about my choices.
So the central problem with road tubeless is that if something punctures your tire, the air pressure is high enough to cause sealant to pinwheel like Chinese fireworks, spraying sealant in spinning rooster tails. No one, in my experience, has made a sealant thick enough to seal a puncture when the tire is inflated to anything more than 40 psi.
The problem here is that you have to be a fool to run 28s at 40 psi. I run 28s at 60-65 psi for tubeless; with tubes, I run the tires 10 psi higher than that.
I didn’t actually see what caused any of my punctures, unlike the hunk of broken coffee mug that once sliced an $80 tubular down to the base tape—and that’s in 1990s dollars. Seeing what had caused my punctures may not educate me, but as I’ve mentioned previously, I’m eternally curious.
The punctures were not large, and let me add that two of them were front punctures, a detail that defies my comprehension. Because they were small, I tried adding additional sealant, turning the wheel so that the puncture was positioned at the bottom of the wheel and gave it time to seal before pumping the tire back up. I can’t say at exactly what pressure the sealant blew out, but it was more than 40 psi and less than 50 psi. On the first attempt, a booger of congealed sealant shot down the driveway, followed by a wet spray of fresh sealant. On my second attempt, I let it sit longer, then added a bit of pressure, maybe 25 psi, enough to force more sealant into the cut.
After letting it sit for several hours I pumped it up to 50 psi, and then got on the bike to see if it would hold. No sooner had I placed one foot on a pedal when a wet whoosh told me no, even before I saw the spray arcing ahead of my bike.
Before I admit that I have given up on sealant as a flat fix for road tubeless, oops, guess I spoiled that, let me say that I do plan to try additional sealants in the future.
One reason I haven’t experimented that much with different sealants and road tubeless is that I’ve simply defaulted to whatever the thickest sealant is I have on hand. Another reason I haven’t experimented that much is that on a mile-for-mile basis, road tubeless does result in fewer flats than traditional clinchers. The exception to this is in wet conditions. Both my front flats with road tubeless came on wet roads.
I ended up cutting plugs in half and inserting them. This involved making the hole in the tire substantially larger than it was. Making a hole in a tire larger is brain-stem-level counterintuitive. Considering the length of the plug tool, this was not easy to do. I had to pinch the tire and push the tool in at a shallow angle to the tire, not directly perpendicular to the tire because the tool would reach the rim long before the plug would go through.
Honestly, I held a fair amount of trepidation about doing this. I was deeply concerned that I would make the hole larger without ever inserting the plug; it took a fair bit of fighting to get the plug through the tire, way more effort than when I’ve plugged an MTB tire, which I’ve only had to do twice in more than ten years of tubeless MTB riding.
Another concern was that the plug would simply blow out once I tried to pump the tire to 60 psi.
I was also concerned that a plug in a road tire was going to result in a bump in the tire that would irritate the hell out of me and if there was a lump that was perceptible, it would have driven me nuts, for sure.
From a tactile perspective, there’s no bump. I have to look to find where the plug went in. I’ve taken the tires up to 65 psi, too.
From now on, I’m only using enough sealant to make sure the tire seals at the rim. I’ll be keeping plugs and CO2 in my saddle bag, in part because I’ve yet to wash all the sealant off the jersey, bibs and knee warmers I was wearing that day.