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Figure 1: Tubeless valve stem |
Chapter 3: inspection, adjustment, and lubrication
Follow these troubleshooting steps in order to minimize the time it takes to repair a leaking tire.
Check the tire pressure on your bicycle before every ride; all tires lose air pressure due to air leaking through the inner tube or tire casing sidewall. If the rate at which air leaks from a tubeless tire is excessive, it might have a puncture causing a leak. The puncture can be reduced by repairing the puncture. Also, you can use Bontrager Super Juice tire sealant in any UST tubeless tire to reduce the rate of air loss and add puncture protection.
A small piece of glass or a thorn can embed in the tread and cause a slow leak.
Air can leak around the seal of the valve stem if it is loose or misaligned. If it is misaligned, loosen the valve stem nut (Figure 1) and gently shift the valve slightly to seat it properly, then tighten the nut. However, do not over-tighten it; if you puncture on the trail, you will have to remove the valve stem nut by hand.
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Figure 1: Tubeless valve stem |
This is a problem that is unique to tubeless tires that are especially light-weight. The inner liner ply (the butyl rubber sealing ply on the inner surface of a UST tubeless tire) is as thin as possible to save weight, and it will break down from hard use. The material will form gaps and these will allow air to escape at increasing rates through the casing. Adding Bontrager Super Juice sealant will stop this type of leak.
These include all of the contact surfaces between the tire, rim strip, and valve. Gaps in the seals due to damage or dirt trapped on any of these surfaces can cause leaks. Clean or replace any damaged parts.
First, visually inspect all components of the tubeless system for damage or evidence of leaks, and simply listen for the sound of escaping air.
If that doesn’t work, cover all of the areas that might be leaking with a solution of soap and water, and watch for bubbles. With this method, you can also find leaks that occur through the tire casing or from between the tire bead and rim strip near the rim wall. Use the same soap and water solution that you use to mount the tires. It’s best to spray the solution on with a household spray bottle so that it is distributed evenly on the tire surface. It’s normal to see some bubbles forming through the sidewall of the tire (a surprising amount!), but a significant leak will cause a very large amount of foam to form quickly.
Sometimes air leaks into the interior cavities of the rim, and these can be hard to find. Sources of these leaks include the area around the valve seal or between the tire bead and rim strip. The leaking air can be detected at the spoke holes, but the location of the actual leak will not necessarily be close to the leaking spoke hole. There are two ways to find and eliminate leaks like these:
· Partially immerse the wheel in a tub of water. Leave it in the tub long enough for the portion of the rim that is underwater to fill with water. Then with your ear close to surface of the water, listen for the sound of bubbles forming as you rotate the wheel slowly in the water. When a leak is at the water surface it will cause a bubbling noise and this will allow you to accurately detect the location of the leak.
· Eliminate the possibility of all other possible leaks. If you have eliminated all visible sources, replace the rim strip or valve stem.
Using Super Juice sealant in any tubeless tire is a huge advantage; Super Juice will seal small punctures and prevent air loss.
You can patch a puncture if it is not too severe, but first you must clean the tire. The inside surface of a tire has release agents on it left from the manufacturing process. Remove the release agents with an abrasive or tire buffer before installing the patch.
A large hole or fracture in the casing will weaken the tire. You should replace a severely damaged tire immediately, or as soon as possible. In an emergency a large patch, called a boot, can be made up of a fibrous material to cover the hole. The boot should overlap the hole by at least an inch in all directions and be bonded firmly to the casing. A tire repaired in this way should only be ridden slowly and used only as long as it takes to get back from the ride.
On the trail, you should not try to patch a tubeless tire that is punctured; it’s best to install a tube.
