Technical FAQ: Sealing tubulars, riding tubeless

This week, Lennard Zinn answers two questions about tires — one on tubulars and another on tubeless.

Sealing tubular tires

Dear Lennard,
I have been running Vittoria CX tubulars on my road bike for the past year and have had a number of punctures. I’ve tried to repair some of them with Vittoria Pitstop but only occasionally managed to get the tube to hold air again. Recently I bought some Stan’s — a lot cheaper — and set about fixing a couple of tubes that have been lying around. Now my problem is that even though the sealant appears to have sealed the puncture, the tube doesn’t hold air nearly as well anymore. I have had this experience both with latex and butyl inner tubes, and I’ve repaired both Vittoria CX tubes and more ordinary Continental Sprinters. The Sprinters deflate in a couple of days, which is fine, but the Vittoria tubes lose three bars or more in a few hours. This is OK for short rides but for Sunday rides it doesn’t really work. Is this what I should be expecting or am I doing something wrong?
— Henrik

Dear Henrik,
You clearly have not sealed all of the holes. I’ve done this many, many times, and, after sealing the holes with sealant, they certainly hold air as long as before, and I usually have the impression that they hold it longer than the normal latex-tube bleed-down time they had before I injected them with sealant.

It’s possible that you have a snakebite (pinch flat), and your sealant filled the hole on the outward-facing wall of the tube but not on the inward-facing wall. Here is a method I have used to fill holes like this; it ensures that the hole on the floor of the tube gets sealant to it, not just the hole on the ceiling of the tube.

Another way to approach this problem is to put A LOT of sealant in there — enough that you figure you’ve filled perhaps half of the volume of the inner tube. Coat the outside of the tire with soapsuds and pump it up hard (100psi or so for a road tubular, 50 psi or so for a cyclocross tubular). Where you see the soapsuds bubbling, rotate that section to the bottom and leave it standing until the soapsuds are no longer bubbling. Keep pumping the tire up, keep coating it with soapsuds, and keep standing it up with any bubbling sections at the bottom. There is so much sealant in it that it will fill holes on the rim side, the tread side, and the sidewall sides of the section of the inner tube that is at the bottom of the wheel.

After all the holes are sealed and you’ve ridden it a time or two (and convinced yourself that it doesn’t bleed air), remove the valve core and squeeze out as much of the sealant as you can. Don’t worry about getting it all out; that’s not your goal. Rather, your goal is to bring the tire down to almost its normal weight and to leave just a bit in there to fill thorn punctures. And when storing it for extended periods, leave the valve closed to prevent the sealant from drying out inside the tube.
― Lennard

In-depth look at Schwalbe One Tubeless blowouts

Dear Lennard,
I wonder what thoughts you might have on my problem. I have several sets of wheels with Stan’s No Tubes Alpha 400 rims. I’ve run them without incident for two years with various Hutchinson Fusion 3 tubeless tires (23s), Hutchinson Intensive tubeless tires (25s), and even Hutchinson Secteur tubeless tires (28s) on my cyclocross bike.

I decided last week to try some Schwalbe One Tubeless tires (23s) on my road bike. Mounted them on one set of my wheels (without using a tire lever) without problems and put Stan’s sealant in them and pumped them to about 105 psi. Within five miles of my first time using them (at about 22 mph on a straight stretch of road, about a 60-degree Fahrenheit day … I’m about 220 pounds) the rear tire blew off the rim. I was able to ride it upright to a stop. The tire was outside the rim on both sides of the wheel.

I spoke to Schwalbe on the phone — very nice and helpful — and they are going to speak with Stan’s No Tubes with whom they have a good relationship (in fact, Stan’s makes Schwalbe’s sealant) to discuss any possible incompatibility issues. Although Stan’s has already told me there are none of which they are aware. Further, my inspection of the tire shows no punctures and although I am not going to ride the tire again, I was able to remount the tire and pump it to about 80 psi just to make sure there was no hole I missed. A day later, it is holding air. By the way — the front tire is fine, so far.

I am really paranoid now. I am very experienced at mounting tubeless tires so I don’t think it was anything I did, but if I did do anything wrong, I don’t know what it might be and I think it would likely be repeated — all I know is this never has happened before when mounting all the Hutchinson tires. Anything peculiar about Schwalbe One tubeless tires about which I should be aware when mounting? They are supposed to be good tires.

Other Questions:

— On the outside chance there is an incompatibility between this particular rim and model of Schwalbe tire, would you suggest going back to using the Hutchinson tires? I know Schwalbe makes good tires but this really spooks me not to be able to pinpoint the reason for the blowout.

— Everyone keeps telling me that only a “true tubeless wheel” when used with a “true tubeless tire” is foolproof (as distinguished from a “tubeless ready” wheel or tire). As I understand it, my Stan’s rims would be considered true tubeless rims except for the fact that their spoke holes in the bed of the rim are exposed and must be covered with mylar tape. I rather doubt that would make any difference from a safety perspective.
— Phil

Dear Phil,
A “true tubeless wheel” features a critical distinction from your wheels beyond simply the difference you mention between holes not piercing the rim bed vs. holes covered by sealing tape. A “true tubeless wheel” has a “hump” along the medial edge of the bead-seat ledge on either side of the rim. This hump not only seals along the medial rubber edge of each tire bead, but it also is intended to act as a beadlock; the tire bead snaps in between it and the bead wall. Photos of this can be seen here. The tubeless rim and tubeless tire system was designed as a system (by Hutchinson) to work together.

I have intentionally ridden a flat rear Hutchinson tubeless road tire down mountain switchbacks to see if it would stay on the rim (a tubeless-compatible Dura-Ace Scandium wheel, which does have the bead humps). It stayed on for over two kilometers of switchbacks before finally coming off on one side.

A tubeless road (TR) tire, like a standard clincher, has high pressures inside trying to yank it straight off of the rim, but, unlike a standard clincher, it lacks an inner tube pushing outward against the beads, and it has tire sealant lubricating its exit from the rim. I know from personal experience that mounting a standard road clincher that stays on the rim just fine with a tube inside will blow right off the rim within a few pedal strokes when ridden without an inner tube and inflated with sealant inside (whether it’s a tubeless-specific rim or any other road rim sealed with a rim strip).

Needless to say, because of that experience, using tubeless road tires is something I went into very carefully. But when my flat TR tire stayed on the rim better than standard clinchers stay on their rims when they are flat, I consider that in the case of a sudden casing cut, they could actually be safer than standard clinchers. I also never run mine higher than 90psi; one of the reasons I use them is that I can run them at lower pressures for increased comfort and decreased rolling resistance without fear of pinch flats. On the other hand, I weigh almost 50 pounds less than you do and understand that you need to run them at higher pressure.

Stan’s design is different from a tubeless-specific rim in that it has low bead walls, a rim-sealing strip, and no “hump.” I don’t know how well the square bead of a TR tire fits into that low bead wall, but I have successfully used Hutchinson Atom tubeless road tires on Stan’s rims for a full season, and many times I’ve run mountain bike and cyclocross tubeless tires on Stan’s rims without problems.

I don’t know if your problem is the tire, the rim, or both. Below are some answers from related manufacturers on this.
― Lennard

From Schwalbe:
I’ve been talking and corresponding with [Phil] about this issue. After we spoke for about 30 minutes yesterday, I agreed to get in touch with Stan’s to see if there was anything about their rim design and our road tubeless tires that suggested that there might be a compatibility issue. I sent an e-mail to Shawn VanEtten at Stan’s, and here is his response:

We try to test all new tires on the market as they come out and the Schwalbe One tire has been one of them. We don’t know too many riders on these tires but do know that we have not had any issues reported back to us until Philip. There seems to be no compatibility issues between the two.

To date, this is the first of our road tubeless tires that have come off the rim. I don’t have precise numbers but we’ve easily sold 2,500-3,000 of the Schwalbe One and the Ultremo ZX Tubeless tires. I ran the ZX tubeless on a set of DA C-24 Tubeless wheels this past summer and they performed flawlessly, and I’m a little north of 200 pounds myself.

I’m not sure what other assurances I can give to this customer. I certainly understand being squeamish about something that didn’t quite work out, especially given the nature of the issue (a water bottle failure would be not as distressing I’m sure) but we simply haven’t had an issue like this crop up. I have offered to warranty the tire in spite of the fact there is no real evidence that it was in fact a tire failure.

On the Schwalbe.com website is listed a number of Road Tubeless rims. The clarification from Germany is that this is a list of “known tubeless rims,” and not specifically a list of rims that Schwalbe has tested and approved. Reading between the lines here, I would say that the engineers at Schwalbe are reluctant to provide assurance about any specific rim when we are not the manufacturer; that responsibility lies with the wheel/rim manufacturer (my interpretation).
— Guy Browne
Customer Service and Tech Support
SCHWALBE NORTH AMERICA
schwalbetires.com

From Stan’s NoTubes:
I have not had any of the Schwalbe tubeless road tires to measure or test. I make a simple bead-checking device that can measure the bead size of the tire. It puts very little force on the bead but can measure the size exactly.

I can tell you a few things. In the past few years we have had at least 10 Hutchinson tubeless road tires snap beads and blow off rims. Hutchinson has always covered them under warranty. It can happen with any tire.

1. If the tire bead snaps you usually cannot get home with a tube unless you run low pressures. Once the bead has snapped that side of the tire will stretch and blow off the rim even with tubes.
2. If the bead just stretches off, it should still work with a tube to at least get you home.
3. Once a tire blows off the rim I would never use it again.

My guess is one bead stretched or snapped.
— Stan Koziatek
Founder, Stan’s NoTubes

From Hutchinson PR:
Speaking only about clinchers as a generic product class, we’ve all seen tires that were difficult to mount or blew off of rims. Was it sloppy ETRTO dimensional standards for the tire, the rim or a combination of the two?

From the beginning with Road Tubeless, Hutchinson was insistent that wheel manufacturers work in partnership to assure that the bead profile on the rim was compatible and offered the mechanical characteristics to properly seal the tire-bead and work with a carbon fiber beaded tire (tighter ETRTO standards).

Now with the growing tubeless tire and wheel presence in the market, what’s happened to that tire-wheel collaboration standard? Hard to say from Hutchinson’s perspective without knowing manufacturing standards and protocols across the market.

Stan’s 400 series wheels use what they call BST technology, which effectively shortens the distance from the top inner section of the rim channel to the top of the bead. Does the bead of the Schwalbe tire not fit as well in this reduced space thus not seating properly?

It’s all speculation at this point as to what actually happened, but with many tire and wheel players in the game, there’s no reason that tubeless tires won’t suffer from some of the same fit problems we see from time to time with normal clinchers.

My recommendation to this particular cyclist would be to stick with Hutchinson tires to allay his fears.
— Richard Goodwin
PR & Marketing Liaison
Hutchinson Tire North America