Super glue (cyanoacrylate glue) isn’t a good solution for fixing punctured inner tubes because it becomes inflexible and brittle upon drying.
In consequence, a patch based on super glue is very likely to fail.
There are two possible ways to patch a puncture with super glue.
The first one is to glue a patch to the inner tube. The second is to directly fill the perforated spot.
Both methods are subpar long-term solutions because super glue doesn’t provide the necessary strength and compliance needed for the normal functioning of the inner tube.
The Inner Tube Has To Be Flexible
The inner tube is constantly changing its shape (deforming) during riding, and when we manipulate its air pressure via inflation and deflation.
For that reason, it’s of high importance to preserve the tube’s original flexibility when patching it.
Super glue doesn’t provide that option because it forms a hard layer.
Over time, the adhesive experience “micro-shattering”, and the bond disintegrates. The final result is “an open wound”.
Why Rubber Cement Is King For Fixing Inner Tubes
Rubber cement is made of two primary ingredients – elastic polymers (rubber) and a volatile solvent that can quickly dry in all kinds of weather conditions.
The main job of the solvent is to keep the elastic polymers fluid before use.
When rubber cement is applied to the punctured spot, the solvent in it breaks down the upper layer of the inner tube and bonds it to the polymers in the fluid.
Once the rubber cement has dried, the solvent is gone, and the inner side of the applied cement is chemically bonded to the outer side of the tube.
The exposed side of the glue is ready to bond because it has free sulfur groups “in anticipation” to connect to others.
A classic inner tube patch has two sides. One is black, the other is orange and covered by foil. The orange side has a bunch of free sulfur groups also waiting to attach to others.
When you remove the foil and press the patch against the dried rubber cement, both sides chemically bond and merge on a cellular level. This process is known as rubber vulcanization.
The end result of those disulfide bonds is a single unit.
This explains why cured tire patches are so difficult to remove. The new patch is practically part of the inner tube.
No instant glue can match the bond while offering the same flexibility. For that reason, standard tire patches based on rubber cement are preferred over improvisation.
Conclusion: Super glue attaches the patch to the inner tube. Rubber cement merges the two pieces into a single unit while preserving the flexibility of the tube.
Temperature Changes Harm Super Glue
Low and high temperatures harm super glue’s bonding strength.
One of the common ways to break a super-glued object without damaging it is to put it in the freezer for a while. At low temperatures, the glue becomes very brittle and so does the bond.
Consequently, super glue isn’t the best option for an item that’s going to be exposed to thermal cycling.
Of course, high-end super glue has good tolerance for temperature shifts, but it’s still affected by extreme hot and cold.
Super Glue Isn’t A Good Inner Tube Filler
Pinhole flats seem like a good opportunity to use super glue as a filler, but that’s not proper practice either.
You can certainly fill a small puncture with super glue, and the patch may even hold for a while, but the method has two notable downsides that make it a poor longterm plan:
1. As the tube inflates, the puncture will become larger too. The augmentation increases the strain on the bond between the periphery of the pinhole and the super glue.
2. Superglue is not flexible and will not expand along with the tube. Consequently, the adhesion could easily fail with use.
Can You Patch a Punctured Inner Tube With Duct Tape?
Duct tape can be very strong, but it’s not a good option for patching a flat tire for the following reasons:
- Duct tape patches could lose air-tightness.
An inner tube has to be completely sealed to function properly. The smallest leak will eventually cause total deflation.
Even if a small portion of the duct tape was to detach, the airtightness of the tube will be compromised.
This outcome increases greatly when running high air pressure. Thus, a road bike’s inner tube patched with duct tape is very likely to fail.
The patch may hold for longer on MTB tires because they’re wider and operate at lower air pressure.
2. Lack of flexibility
Duct tape isn’t elastic and will prevent the patched spot from expanding as necessary. The restriction will result in an uneven expansion and possibly a deformed tire.
In some situations, the wheel may feel lumpy.
3. High Temperatures Affect The Bond
The likelihood of failure increases in hot weather because high temperatures have a negative effect on adhesives.
4. Weaker Than a Regular Patch
By definition, a duct tape patch cannot provide the bonding strength of a puncture kit because the bond is adhesive-based.
Meanwhile, a regular patch is bonded to the inner tube on an atomic level.
Having said that, if nothing else is available, a piece of duct tape may do the trick and get you back home, but it shouldn’t be used as a long term solution.
If you have to rely on duct tape, it’s recommended to keep the tire at its lower pressure rating to reduce the stress on the patch.
Can I Use A Piece Of Inner Tube as a Patch?
Yes, a piece of inner tube can work as a patch, but only if it’s really clean.
Contaminations such as the powder found on inner tubes will prevent the patch from bonding.
Also, you have to follow a different protocol when applying the patch.
Here are the necessary procedures:
- Cut a piece of an inner tube, clean it with soap and water. Let it dry.
- Sand/Abrade one side of the inner tube patch.
- Find the puncture on the inner tube that has to be fixed and prepare the spot for patching by sanding it and then applying rubber cement.
- Apply rubber cement/vulcanizing fluid to the sanded side of the inner tube patch.
- Wait for 5-10 minutes (the rubber cement has to dry)
- Inflate the inner tube a bit to pre-stretch it.
- Apply the patch on the inner tube.
- Wait 5-10 minutes and reinstall the tire.
The downsides of using a piece of an inner tube as a patch are:
- Extra work and time
When using a piece of an inner tube as a patch, you have to sand it and apply rubber cement on it.
If you don’t, it won’t stick to the inner tube because it doesn’t have a side with free sulfurs like a standard patch.
The extra steps complicate the procedure and increase the chances of complications. This is particularly annoying when patching a tire on the road.
- No tapered edges
Classic inner tube patches have tapered edges making it harder for the patch to peel off with use. Homemade inner tube patches, on the other hand, “stand tall”.
- Extra Rubber Cement
In this case, each patch uses twice as much rubber cement and reduces the money saved from relying on an improvised solution.
Conclusion: While it’s possible to use a cut piece of inner tube as a patch, this option is sub-optimal, especially for emergency fixes.
Note: If you try to apply the inner tube patch via super-glue, the bond won’t be strong enough to sustain the demands. The chances of compromising the air-tightness of the inner tube are very high.
What About Flexible Super Glue?
Some super glue products have an altered formula providing more flexibility. While they may do a better job at patching a tire, they will never be able to match the bonding strength and flexibility that a standard rubber cement solution offers.
Also, higher-end glues are often more expansive than a designated repair kit.
Super Glue Can Be Useful For Repairing Small Tire Cuts
Regardless of how expensive and “advanced” a tire is, if you use it long enough, it will begin to accumulate mini cuts caused by small stones and pieces of glass.
One of the cheapest and fastest ways to mitigate the damage is to get out the small bits of stone and glass with a pointy object and then fill the cracks with super glue.
Of course, even in this case, the super glue’s inflexibility is a downside. Sooner or later, the cut will open, which is why some people use rubber glue (e.g., Shoe GOO).
Having said that, the price of generic super glue and the fact that the outer tire does not have to be 100% airtight when you’re running an inner tube, make superglue an acceptable solution.
However, if the cut is really deep, you may have to sew or replace the tire.
Back in the day, I got a “through and through” 1cm cut on my rear tire after jumping from a curb and landing on a piece of glass.
To prolong the life of the tire, I applied an inner tube patch on the inside and super glue on the outside. The solution worked for a while, but eventually, the super glue fell off, and I had to reapply it.
Key Takeaways
1. Super glue is not good for fixing a pierced inner tube because it’s inflexible and brittle. Therefore, it should be used only as a last resort.
2. Standard tire patches that come with rubber cement make the strongest bond and can hold for years.
3. Duct tape is strong, but it’s not a good patch because it’s highly inflexible. Also, it can partially peel off and kill the airtightness of the tube.
4. Super glue is an acceptable solution for fixing small cuts in the outer tire.
