Tubeless leaking air might be the most annoying thing to service for most folks. I could say it was for me as well for a very long time. Luckily, with experience comes a different approach and much better analysis. Now, I can pretty much say what’s wrong with it in the first minute of looking at it, but some problems still require more work to figure out.
One of those problems is the tubeless valve stem leak. Some people will say it’s easy; they will claim that it’s something with the tape or the valve itself. However, you can only guess the problem unless you remove the tire and take a perfect look at it. And that is the problem because you end up removing and reinstalling the tire several times until you get it right.
That is why I’m writing this article to explain all the possible things that can cause this problem and fix it. Or even better, prevent it altogether.
Tubeless valve stem leaking has two causes. The tape is damaged or improperly installed, or the tubeless valve is not sealing airtight. To prevent it from leaking, the tape needs to be checked and fixed if necessary, and the air gap around the valve needs to be sealed properly.
How Tubeless Valves Work
Now that I’ve given you a short answer about tubeless valve leaking, it’s time to go into details. But first, we should start by explaining how tubeless works in the first place for people who are new to this.
The tubeless system doesn’t have a tube to hold the air but instead seals the whole space between the rim and tire to prevent air from getting out. There needs to be a rim tape or a rim strip that will close the rim spoke holes to seal the air. Those holes usually have sharp edges and are quite big, so the tape must be durable enough to last.
A tubeless valve is a separate part with a sort of a rubber seal to close the valve hole on the rim and seal it completely. It’s tensioned from the other side of the rim by a locknut, which you can usually see on tube valves as well.
When it comes to the tire, it has to be tubeless-ready. Normal tires have weak sidewalls, which often leak air unless paired with a tube. Tubeless ones hold air in the same way as a tube does, while the tire’s bead sticks to the rim and preferably to the rim tape as well to seal the system on that end.
If there are still any tiny gaps left, there is a sealant that you have to pour inside to seal those off. Not only that but if you get a puncture, the sealant will close the hole as it transforms into a rubber.
To understand the problems that occur with tubeless setups and prevent them, we must look at which tapes and tubeless valves work best and why.
Best Tubeless Tapes and Rim Strips
I won’t give you a list of the best tubeless tapes, mainly because I always use two layers of Gorilla Tape. I find it the easiest to install properly, and it works amazingly well. However, it has some drawbacks like weight, and replacing the tape can be difficult because it’s so sticky.
I will try to explain and categorize rim tapes and rim strips to decide for yourself which are the best.
Tubeless Rim Tapes
The problem with tubeless tapes on the market is usually the weight saving over quality the manufacturers prefer. So basically, the best tubeless rim tapes will be the ones that come in the middle of these weight-saving low-quality ones and the robust ones like Gorilla Tape.
What is the most important about tubeless rim tape is that it’s sticky enough. Some of these tend to leave a lot of air bubbles and gaps between the tape and the rim, which causes air leaks sooner or later.
The second most important thing is how well it mixes with sealant. Because the sealant is liquid, it will dissolve the tape’s glue if there is any gap left. In time you have a problem because it will slowly become a bigger and bigger surface where there is no glue anymore, and it will start leaking air.
When it comes to material quality, it will be good enough for mountain bikes if it is made for tubeless. All you need to make sure is that the tape is wide enough for your rim. You can always cut it to fit the rim as long as it is the right size or bigger than your rim.
I found that most of those “best” tubeless rim tapes that everyone praises on the internet are actually the worst and are praised by the people who never really tried multiple tapes.
Tubeless Rim Strips
Tubeless rim strips are the best if you can find the right one for your rim combined with a fitting tubeless valve. That is their main issue. They need to fit the rim they are used on. That’s why tubeless rim strips are slowly disappearing from the market, with too many compatibility issues.
However, some rim and bicycle manufacturers put them with their products and have them available for purchase. If you ever decide to go with these, here is what you need to be careful about.
As already mentioned, the size must fit your rim flawlessly. Without that, you won’t make it work because they are not as soft as rim tapes, and the tire won’t sit properly.
The second issue can be tubeless valve compatibility. That part of the valve that seals the hole from the inside comes in lots of shapes. Rim strips are kind of sensitive to which shape it is because they don’t flex at all.
Best Tubeless Valves
Once again, not a list but a categorization of what is good and not about certain tubeless valves.
What it really comes down to is the part that seals the hole. As mentioned above, it can cause a lot of trouble with tubeless rim strips. However, the same goes for the rim shape as well.
There are three common types of tubeless valve seals.
The oldest one is probably in the shape of a rubber block. It’s basically a Jack of all trades but master of none. The seal is good, but the shape can cause problems, especially when you try to tension it. If the whole valve turns, the rubber block will either damage the tape or create a gap for the air to flow out. So that’s the one thing to be careful about with them.
A bit rare these days, the second one has a metal block with a rubber o-ring seal on it. The seal on this valve is perfect, but the shape again causes way more problems than the rubber block one. That’s probably the reason why we don’t see it so often anymore.
And third, most popular these days, the cone-shaped rubber seal tubeless valve. This one is amazing, but it has one problem that often happens during installation on rim tapes. On rim tapes, you need to open a valve hole by yourself, and if you don’t open it wide enough, the cone will get loose all the time. Sometimes it starts leaking air and sometimes doesn’t, depends on the sealant. An easy way to prevent this is to make sure the hole is opened all the way to the edges of the valve hole on the rim. That way, it can’t widen anymore, and the cone will fit perfectly with any tubeless rim tape or rim strip.
Why is My Tubeless Valve Stem Leaking?
Now that we have gone through all the types of both rim tapes and valves, you can quickly check which ones you have and what could be the problem with them. The most common problems that I found as a bike mechanic are either the tape is badly installed because it doesn’t stick to the rim well enough, or the valve isn’t sealing properly for one of the reasons mentioned in the text above.
If any of that looks completely fine, try checking if your rim tape is broken somewhere. It should be a very tiny hole or a barely visible cut.
Most of these problems can be fixed and prevented, and here is how.
How to Fix Tubeless Valve Stem Air Leaks
If it’s a cone-shaped valve seal, then first make sure the rim tape valve hole is opened completely. Try to push the valve with your finger to see if there is any more room there. At the same time, turn the locknut on the other side clockwise to tension it. That will make sure the gaps are sealed.
If it is all the way in and there are leaks, there may be a small cut on the rim tape just next to the valve. As the cone is pressured in and the tape hole widens, sometimes it can break if it gets jammed a bit. Check if that’s the case, and if it is, you can always tape a small part of the rim with a patch of new tape to close it off.
If the valve seal shape prevents the valve from sealing airtight, you have two choices. Changing the valve or adding something that will seal the gaps. I like to use small rings that I cut from an old tube. You can cut them in different widths and shapes to fit properly and sometimes add more than one. You can use O-ring seals, but sometimes they are too thick and can’t bend properly to the shape you need.
If you can’t get it right because the rim shape is horrible, you can always add a patch or two of rim tape just on the hole area. That way, the thickness you get from the tape can be squeezed by the valve seal better and seal it that way.
How to Fix Tubeless Tape Leaks
It might be that the valve stem leak is actually caused by rim tape leaking, as I already explained. As a matter of fact, it happens to be so in like 50 percent of cases.
If the tubeless rim tape is coming loose because the glue isn’t good enough you will have to change the whole tape. There is simply no way to fix this, at least not long term. Try with a stickier tape this time.
If the tape is cut or broken somewhere, you can clean its surface and tape a patch of new tape over it. The tape usually breaks over spoke holes on the rim because the edges can be sharp. While you are at it, check the other spoke holes as well. If there is one, there might be more. At some point, it might be easier to tape a whole new circle or replace it altogether.
All in all, air leaks in tubeless setups are not something to be bummed about. It happens a lot, even to us that installed thousands of them. To prevent this from happening, I always have a few O-rings or custom-made ones that I can put on the valve if I feel it could cause trouble. Also, taking real care when installing the tape will lose you a few more minutes but you save yourself a lot of trouble in the future.