TPU tubes are gaining attention as the third force in bicycle tires. We summarize its features, advantages and disadvantages of using it on road bikes and MTBs, and major manufacturers.
Table of contents
Causes of tubeless tire bead not coming up
*In this case, we will assume that there is no air leakage from the tubeless valve or tubeless rim tape, i.e., the bead not coming up is “only caused by the rim and tire”.
“The outer circumference of the wheel rim bed is too small” or “The inner circumference of the tire bead is too large.
The biggest challenge in tubeless conversion is the compatibility between the wheel (rim) and tubeless tire.
Tubeless tires, which must strictly conform to ETRTO standards, are manufactured in a very strict manner with regard to size, but even so, as they are industrial products, there will be some errors. It is up to the manufacturer to decide whether to allow for a “larger” or “smaller” margin of error.
Wheel makers believe that the smaller the error in the outer circumference of the wheel rim, the easier it is to fit the tire (to avoid cases where the tire cannot be mounted), while tire makers believe that the larger the error in the inner circumference of the tire bead, the easier it is to fit the tire (to avoid cases where the tire cannot be mounted). The tire manufacturer thinks that a tire can be mounted on a variety of rims if the error of the inside circumference of the bead is “large”.
If this is the case, the combination of “a wheel that allows a smaller error on the inside of the rim” and “a tire that allows a larger error on the inside of the bead” will be smaller on the inside and larger on the outside than ETRTO assumed, resulting in a gap that makes air leakage more likely and bead raising more difficult.
This is the reason why tubeless wheels and tubeless tires are compatible with each other.
Tire bead is hard.
When raising the bead of a tubeless tire, the process is as follows
- the tire itself expands and spreads
- the bead at the center of the rim is pushed out toward the rim wall
- the pushed bead “rises” to the rim step
At this time, the bead does not rise all at once, but always gradually rises from one part at a time, and the closer to the tire’s specified pressure, the more the bead rises as a whole.
Incidentally, bead raising has an image of “slamming sound”, but the bead is coming up even if there is no sound. The only part that makes noise is the “hard-to-raise” part, which requires force to raise the bead.
When the bead is raised, the bead is naturally skewed or twisted because there are areas where the bead is “raised” and areas where the bead is “not raised.
If the bead is a hard tire, it will not be at an angle while adhering to the rim, but will be extremely twisted and bent, resulting in a lower degree of adhesion to the rim. This creates a gap between the rim and the bead, causing air leakage.
The hardness of the bead depends on the thickness, material, and shape of the bead, and in some cases, even if the bead is hard, it will come up straight, depending on the inside shape of the rim.
Solve the cause of the bead not coming up!
Once you know the cause of the bead not coming up, let’s solve the cause and prevent air leakage.
Solve the compatibility problem
First, solve the compatibility problem with the tire.
The whole process is as follows.
- try to frame the bead a little by hand and inflate it
- if it doesn’t work, put a tire tube in and raise the bead, then remove the tube while keeping the bead raised on one side
- again try to frame the bead by hand and inflate
As explained earlier, many tubeless compatibility problems come from size differences within the respective error ranges, and most are caused by “gaps due to large differences between tires and rims”.
Therefore, after using tubeless tires to some extent, you will be able to tell that “this combination is suspicious because you can easily fit the tire by hand (the difference will be large)”.
Conversely, if the difference is large, it means that the circumference of the tire bead is large in relation to the rim, so the bead can actually be raised by hand. So, let’s try to raise the bead by hand as much as possible.
To raise the bead by hand, all you have to do is “pinch the side of the tire a little and pull it toward the rim. With this alone, you can raise the bead up to about 60% of the total bead, depending on the combination. However, air leaks often occur in the remaining 40%.
If raising the bead by hand does not work, then once the tube is in place, we can deal with the problem.
- raise the entire bead with a tube
- leave the bead raised on one side and pull the tube out from the other side
- replace the valve with a tubeless valve
- place the bead that has come off inside the rim, being careful not to let the bead on one side fall off
- fit the bead that is not raised by hand
The aim is to reduce air leakage by raising the bead on one side only. When the bead on one side is raised, the tire will be tighter (tighter fit), which will also reduce air leakage in other areas.
If the bead on one side is raised, the bead on the other side may be raised simply by pumping normally. If it does not, raise the bead as far as you can by hand as before.
If that does not work, find the area where the air leak is located and raise the bead by hand, focusing on the bead for that area.
Let’s smooth out a stiff bead.
As you raise the bead by hand, you will notice areas where the bead is kinked or slanted. When you inflate the bead, you should see a sizzling air leak from there.
This area may be kinked due to high resistance when the bead is raised, so use soapy water or foam type hand soap to reduce the resistance (make it more slippery) and help the bead raise smoothly.
You can apply soapy water to the bead from the beginning, or you can apply it to the area of air leakage while the bead is still somewhat raised, which has the advantage of allowing you to check the area of air leakage.
Once the soapy water has been applied, the bead can be raised by hand as described above, while looking for the area where the bead can be successfully raised.
If that doesn’t work, you have to use boosters, etc.
If the floor pump does not raise the bead after all this work to raise the bead, you will have to use a tire booster or CO2 cylinder.
If you want to try it for minimal cost first, use a CO2 cylinder, which will only cost you about $15. You can also use the extra CO2 cylinder as a portable pump on your rides to save weight in your luggage.
|Compatible Vulve||Schrader, Presta|
If that does not work, use a booster. Schwalbe’s booster is the standard tire booster with a high reputation and a stable stock.
|Maximum Air Pressure||11bar|
For more information on the types of boosters and how to choose one, please refer to the following article.
Here is a summary of how to raise the bead on tubeless tires.
Regarding raising the bead of tubeless tires, there are cases where a booster or CO2 cylinder can solve the problem immediately, but on the other hand, there are also cases where even pro stores “cannot raise the bead even if they use a commercial compressor.
Considering such a situation, it is better to know the cause of bead not coming up and the device to solve the cause, so as to have a guide when dealing with the problem.