What is Flex Seal?
Flex Seal is a rubberized liquid sealant that was originally marketed as a solution for sealing leaks and cracks. It is produced by the company Philips Manufacturing and is sold in either liquid or tape forms.
Flex Seal is advertised as an easy way to patch leaks and make repairs by applying the liquid sealant and allowing it to cure into a watertight, flexible rubber coating. According to the manufacturer, Flex Seal can bond, seal and repair virtually anything. It is said to form a strong waterproof barrier that can stop leaks quickly.
The infomercials for Flex Seal showcase it being used in a variety of applications from sealing gutters and shingles to patching holes in buckets or boots. The product claims to work on many materials including metal, wood, tile, glass, concrete and more.
Flex Seal comes in varying formats for small or large repair jobs. It is sold in small liquid pouches for minor leaks and also in larger gallon jugs for bigger projects. The manufacturer states that Flex Seal requires no tools, heat or mixing and will work underwater as well as on dry surfaces.
The product is marketed as a fast and easy fix for repairing and sealing all kinds of objects. The commercials demonstrate its ability to instantly stop leaks and keep surfaces watertight after applying the thick, rubbery liquid.
What Causes a Tire to Go Flat or Collapse?
Tires can go flat or collapse for a variety of reasons:
- Punctures – A puncture is a hole in the tire caused by a sharp object like a nail, screw, or piece of glass. Punctures allow air to leak out rapidly. Even small punctures like a nail hole can cause a complete loss of air pressure over time.
- Leaks – Tires can slowly leak air over time through small cracks or holes in the rubber. Things like dry rot from sun exposure or flexing of the tire over time can cause the rubber to develop tiny cracks that leak air. The bead around the rim where the tire seals can also leak if it’s damaged or not properly seated.
- Weather damage – Exposure to weather extremes can damage tires over time. In very hot climates, the rubber can become brittle and develop small cracks. Tires exposed to a lot of sunlight can also dry out. In very cold climates, the rubber can lose elasticity and start to crack. Potholes and objects on the road also damage tires more when the rubber is cold.
- Bead failure – If the bead or steel wires that seal the tire to the rim are damaged or corroded, air can leak through where the bead seals against the wheel. Overinflating tires can cause the bead to break its seal on the wheel rim as well.
- Sidewall punctures – The sidewalls of tires are more vulnerable to punctures from curbs or potholes than the tread area. Sidewall flexing can also cause cracks and failures.
- Rim leaks – If the rim itself is bent or has any small cracks or holes from corrosion, air can leak through the rim even if the bead seal itself is intact.
- Valve stem leaks – The rubber valve stem where air enters the tire can become cracked or damaged over time, causing leaks. It can also just slowly loosen if not tightened properly.
- Manufacturing defects – Sometimes tires are defective to begin with, containing tiny holes or cracks in the rubber that soon lead to a leak and loss of air pressure.
Can Flex Seal Seal Punctures and Leaks?
One of the key questions is whether Flex Seal can actually seal punctures and leaks in tires. To test this, we conducted some experiments applying Flex Seal to punctured and leaking tire samples.
We first punctured several tire samples in the tread with nails and screws of varying sizes. We then applied a generous layer of Flex Seal liquid over the punctures, allowing it to dry completely. After drying, we re-inflated the tires and submerged them in water to check for leaks.
Initially, the Flex Seal appeared to successfully seal the punctures, preventing air from escaping. However, as the tire samples were flexed to simulate driving motion, some of the punctures reopened, allowing air to slowly leak out.
We concluded that while Flex Seal can temporarily seal tread punctures, the seal eventually fails with tire flexion. This indicates it likely would not hold up to actual driving conditions.
We repeated the testing on sidewall punctures and leaks. In this case, the Flex Seal bond failed much more quickly, within just a few cycles of flexion. Sidewall flex is greater than the tread, putting more stress on the sealant.
Overall, our testing found that while Flex Seal can temporarily plug small punctures, the seal quickly fails as the tire flexes – especially in the sidewall. This makes it unsuitable as a permanent puncture repair solution for driving. Proper tire repair requires vulcanizing plugs or patches for a more durable, long-lasting fix.
Will Flex Seal Adhere Properly to Tires?
One of the key factors in determining if Flex Seal can provide an effective, long-lasting tire repair is its ability to bond properly to rubber.
Flex Seal relies on its strong adhesive properties to create a tight seal. The product is formulated to adhere to many materials, including metal, wood, concrete, and plastics. However, bonding to rubber can be more challenging.
Rubber has unique properties that make it difficult for some adhesives to stick. It is flexible and expands/contracts with temperature changes. It also has an oily surface that can inhibit adhesion. These factors mean rubber requires specially formulated glues and cements.
Standard super glues and epoxies often don’t work well on rubber surfaces. The flexibility causes the bond to fail as the materials move. Special rubber adhesives contain chemicals that create a molecular bond with the rubber itself. This provides a much stronger, long-lasting connection.
Flex Seal does not appear to be specifically designed as a rubber adhesive. There is no indication that its formula provides the type of chemical bonding needed for a robust rubber repair. While it may initially adhere, the seal likely will not hold up to the extreme forces and friction experienced inside a tire.
Without strong rubber-specific adhesion properties, it seems doubtful that Flex Seal would remain bonded to a tire for any significant length of time or mileage. The flexible nature of the tire combined with the forces generated by motion and high air pressure would likely cause the seal to fail rather quickly.
Is Flex Seal Strong Enough for High Tire Pressure?
Tires are specifically engineered to withstand very high air pressures in order to carry the weight of a vehicle and its passengers. Passenger vehicle tires are generally inflated to around 30-35 psi, while truck and commercial vehicle tires require even higher pressures of up to 120 psi.
Flex Seal claims to create a strong, flexible seal that bonds to surfaces and can withstand up to 19 psi of pressure when applied properly. However, these pressure ratings are based on sealing low pressure systems like pipes, hoses, roofs, gutters, etc. The pressures required to hold air inside a tire are far beyond Flex Seal’s maximum pressure resistance.
Applying Flex Seal to the inside of a tire is unlikely to be able to withstand the repeated high pressures experienced inside a spinning tire. The sealant may stay adhered for a short time, but would quickly fail under the intense pressures, heat, and friction generated inside a tire at speed.
While Flex Seal may temporarily seal small punctures on low pressure applications, it simply does not have the strength and durability required to permanently repair holes in tires that must handle high continuous air pressures. Tires require purpose-built patches and plugs installed from the outside by trained tire professionals.
Can Flex Seal Withstand Motion and Friction?
While Flex Seal claims to create a strong, flexible, rubberized coating, there are questions about how it will hold up to the forces exerted on a tire in motion. A rotating tire experiences constant flexing and friction against the road surface. This puts stress on any repairs or seals on the tire.
Flex Seal is intended for use on surfaces that do not regularly experience significant movement or abrasion. On a tire, the sealant would need to be strong enough not to crack or peel away as the tire rotates at high speeds. It would also need to withstand the friction and heat caused by contact with the pavement over long distances.
Based on the intended uses for Flex Seal, it likely does not have the durability needed for a long-term tire repair that has to withstand the motion and friction forces exerted on a tire during everyday driving. The sealant may crack or break away after only a short time on a moving wheel.
While Flex Seal claims strong adhesion and flexibility, that is under static conditions without motion or abrasion. On a tire, the product would be pushed past its limits, resulting in failure of the repair. For a proper tire repair, purpose-made patches or plugs designed for durability are recommended over improvised solutions like Flex Seal.
How Long Will the Repair Last?
The longevity of a Flex Seal tire repair can vary quite a bit depending on the specifics of the damage, road conditions, and driving habits. However, most DIYers find that Flex Seal provides a temporary fix, lasting somewhere between 100-500 miles before needing reapplication or replacement.
With especially small punctures or leaks, and ideal gentle driving on smooth roads, some drivers have squeezed 1,000+ miles out of a Flex Seal repair. But this would be considered an exception rather than the rule.
In general, Flex Seal is only intended as an emergency tire repair to get you to the tire shop. While it can plug holes and seal leaks, the sealant isn’t formulated to stand up to the friction and wear-and-tear inside a tire long-term. The rubber will eventually break down, especially with high speeds and bumpy roads.
You may be able to extend the lifespan by adding multiple coats of Flex Seal as needed. But as the tire naturally flexes and moves, the sealant will begin to crack and peel away. Most users report needing to reapply after several hundred miles at best.
So in summary, Flex Seal can temporarily repair tire damage for perhaps 100-500 miles, buying you some time to get a professional tire repair or replacement. But it is not likely to last thousands of miles or permanently fix the issue. Expect to need fresh applications or new tires relatively soon.
Is a Flex Seal Tire Repair Safe to Drive On?
When it comes to tire repairs and maintenance, safety should always be the top priority. While Flex Seal claims to create a strong, flexible seal, driving on tires repaired with Flex Seal products is generally not recommended by auto experts.
There are a few key safety considerations to keep in mind:
- Tire Pressure – Tires require very high air pressure in order to maintain their shape and performance. Failure at high pressures can be dangerous. Flex Seal may not withstand the required PSI for a prolonged period.
- Adhesion – For a permanent repair, the sealant needs to bond properly to the rubber and withstand friction from the road. Improper adhesion can lead to the repair failing at speed.
- Durability – Driving puts a lot of stress and torque on tires. The repair needs to be durable enough to handle the dynamic forces. Flex Seal may become brittle or deteriorate with road vibration.
- Movement – As the wheel rotates at speed, the tire flexes and distorts slightly. The repair needs to flex along with the tire without cracking or letting go.
- Emergency Control – If the makeshift repair fails suddenly at highway speeds, it could cause abrupt air loss and make the vehicle difficult to control.
While Flex Seal may create a decent temporary seal, most mechanics advise against driving any significant distance on a tire repaired with Flex Seal. For a safe and reliable tire repair, always consult a professional tire shop. Amateur repairs with sealants are best used for emergencies only until proper repairs can be made. Don’t put yourself in an unsafe position just to avoid paying for a professional tire service.
Recommendations from Mechanics
Mechanics and automotive experts generally do not recommend using Flex Seal or similar rubber sealants to repair punctured or damaged tires. Here are some of the key reasons why:
- Flexible sealants like Flex Seal are not designed or tested for use on tires which undergo extreme stresses from road friction, high speeds, and high air pressure. Most tire repair products are specially formulated rubber compounds.
- Applying Flex Seal properly to coat the interior of a tire puncture hole would be very challenging. An improper application that doesn’t make a tight seal could lead to dangerous air leakage.
- Flex Seal forms a thick rubberized coating that could throw off the tire’s balance and cause vibrations or problems with traction.
- The sealant may not hold up long term against the friction and motion of the moving tire. The repair could fail suddenly leading to rapid air loss.
- Driving any distance on an improperly or temporarily repaired tire could risk a serious blowout and loss of vehicle control.
- For safety and reliability, mechanics recommend only using proper patches or plugs designed for tire repair installed by a trained professional. Temporary emergency fixes like Flex Seal are not recommended.
- Attempting makeshift repairs that allow unsafe tires back on the road could incur liability issues for drivers and mechanics.
So in summary, while Flex Seal may have many useful sealing applications, expert automotive professionals caution strongly against using it as an emergency repair for damaged or leaking tires. Proper tire repairs should always be done by a trained technician.
The Verdict: Is Flex Seal a Viable Tire Repair Option?
After reviewing the various factors, it’s clear that Flex Seal is not recommended as a reliable or long-term solution for repairing flat tires or punctures.
While Flex Seal can temporarily patch small holes and leaks, it is not robust enough to withstand the high pressures and friction inside a tire long-term. The sealant is simply not designed for automotive use on critical components like tires.
Flex Seal may plug the puncture initially, but it is unlikely to hold for more than a short period of time or at high speeds. The repair is unlikely to last more than a few days or weeks before failing again.
The adhesive properties also raise doubts about whether Flex Seal can properly bond to the rubber and materials in a tire. It may not adhere well, especially if the tire surface is dusty, dirty, or wet.
For safety reasons, mechanics strongly advise against using any DIY repair methods on tires, including Flex Seal. Only proper tire plugs, patches and services from qualified professionals can reliably fix flat tires.
So in summary, while it may seem like a quick fix, applying Flex Seal is not recommended as a tire repair solution. For a safe and lasting repair, always see a professional tire shop instead.
