Understanding the Chemical Bonding in Tire Plug Repair

[jake jot]

This is one method to fix a tire with hole.



I'd like to understand what happens mechanically to the tire belts and plies when plug method was used to fix the hole. This is part of a tire.

Now imagine you push a tool into the hole (like in the video), would the belt and ply simply have clean holes or would the section of the belt and ply be pushed outward such that there is slight separation between the tread and belt/ply? If you have spare tire with puncture that you don't need anymore. Can you try pushing a sharp object into a hole to see what would happen (like how it would puncture the belts and plies)? Thank you.

 

[Ranger Mike]

I had a flat tire caused by roof nail. I just had roof replaced. I pulled out the nail. It had gone in at an angle and not perpendicular to the tire tread. I took a 1/8" drill bit and using a power drill made a hole thru the tire tread. I inserted the tire " rope" into the notch of the tire tool so that the rope was divided equally on each side of the notch. I then pushed the rope into the tire and extracted the notch tool. I put compressed air into thetire and checked for leaks with a spray bottle of windex. Was good to go. Still has not leaked and it has been a month.

 

[DaveE]

It's not too hard to find "best practice guidelines" out there. In the real world there are lots of ways to do repairs that seem good enough for a while.

"It is NHTSA’s position that a combination repair is the only way to properly repair a tire puncture. A combination repair consists of a repair patch with a rubber plug/stem attached to its center. "
https://www.carabinshaw.com/unsafe-tire-repair-methods-persist-despite-strong-evidence-of-da.html

Or, the repair section of this document:
https://www.ustires.org./sites/default/files/CareAndService_PassengerAndLightTruckTires_0.pdf

I think one of the hardest questions in the engineering world is: "I did something wrong, how bad is it?"

 

[Baluncore]

... would the belt and ply simply have clean holes or would the section of the belt and ply be pushed outward such that there is slight separation between the tread and belt/ply? ...

It depends on the damage. If the tensile fabric of the tire has been cut, then it can no longer carry the tension, so it must not be repaired with a plug. Since the sidewall of the tire has minimum fabric and maximum flexibility, it must never be plugged.

Normally a spike such as a thorn or a nail will separate the parallel fibres in the fabric, but hopefully not cut them. The fibres can then be separated further as a plug is inserted. The plug is then pinched by the tension in the fabric as the tire is inflated. The glue on the plug will seal the hole in the rubber.

Since inserting a plug will distort the tension in the fabric, plugs must be separated by a minimum of 120° about the tire. That way, two plugs will not place undue load on the same fibre.

 

[jake jot]

It depends on the damage. If the tensile fabric of the tire has been cut, then it can no longer carry the tension, so it must not be repaired with a plug. Since the sidewall of the tire has minimum fabric and maximum flexibility, it must never be plugged.

Normally a spike such as a thorn or a nail will separate the parallel fibres in the fabric, but hopefully not cut them. The fibres can then be separated further as a plug is inserted. The plug is then pinched by the tension in the fabric as the tire is inflated. The glue on the plug will seal the hole in the rubber.

Since inserting a plug will distort the tension in the fabric, plugs must be separated by a minimum of 120° about the tire. That way, two plugs will not place undue load on the same fibre.

Do you know what would possibly happen if the installer put oil first in the hole before inserting the rubber plug? I notice they do it in some repair centers. They use engine oil so the plug can be inserted easier. And they never use a glue. The hole is in the bottom tread and not sidewall of tires.

What can engine oil to the rubber plug? Can it melt the edge of it?

What can engine oil do to the tires rubber, belts and plies?

I know it is wrong to use oil instead of glue but I just need to know the technical reasons of what could possibly happen, can the rubber plug slip because of the oil? Don't worry I will never have this done to my car but I just noticed it happened to other cars.

 

[jsgruszynski]

This is one method to fix a tire with hole.



I'd like to understand what happens mechanically to the tire belts and plies when plug method was used to fix the hole. This is part of a tire.

View attachment 294849

Now imagine you push a tool into the hole (like in the video), would the belt and ply simply have clean holes or would the section of the belt and ply be pushed outward such that there is slight separation between the tread and belt/ply? If you have spare tire with puncture that you don't need anymore. Can you try pushing a sharp object into a hole to see what would happen (like how it would puncture the belts and plies)? Thank you.

The technique does work. I've had it done many times.

The impact on the belts is pretty small: calculate the area of any given belt and then the area the puncture and patch - it's going to be between 1000:1 or 10,000:1 in area ratio depending on the tire size. For engineering purposes that kind of ratio generally means "no noticeable reliability issues" because the entire rest of the belt can take up the strain and provide sufficient strength. If it got below 10:1 it would become a worry.

BTW the tire shop that used to fix my tires this way only charge US$ 10 and I was in-and-out in 15-20 minutes. That's cheaper than replacing the entire tire every time I get a flat "just in case". So the economics also work really well hence it's popularity.

 

[Tom.G]

Just a Heads-Up for others reading this.
Do NOT try the method in the video on a tubeless motorcycle tire. The rope plug removes itself in roughly 20 miles (30km)... and that is riding slowly on surface streets. Speeding along on a highway would be inviting a forever visit to a cemetary.

Keep the shiny-side up,
Tom

 

[Baluncore]

The impact on the belts is pretty small: calculate the area of any given belt and then the area the puncture and patch - it's going to be between 1000:1 or 10,000:1 in area ratio depending on the tire size. For engineering purposes that kind of ratio generally means "no noticeable reliability issues" because the entire rest of the belt can take up the strain and provide sufficient strength. If it got below 10:1 it would become a worry.

It is not the area but the number of long fibres that are disrupted that is important. That is not an area problem, it is a more critical linear problem.

Tire plugs come as either impregnated rope plugs inserted from outside, or as rubber mushroom plugs, that are inserted from the inside, with an integral internal patch. Both should be installed with rubber contact adhesive.

Engine oil, and more particularly diesel fuel, may soften an older dry tire. I would keep both well away from rubber tires. They will modify the friction properties of the rubber on the road. There is no telling what will happen when engine oil is absorbed into the tire fabric. I expect the rubber will become softer and swell which might make a better short term repair. But the last thing you need is to lubricate the internal fibres of the tire where they are bonded to the rubber. Best seal that hole with rubber cement.

Water is a natural lubricant for rubber, but it is not a good glue. Once you have a nail part way into a dry tire it may stop there and wear against the road for a while. But when it rains and the tire gets wet, the nail may advance further to complete the puncture.

Internal air pressure prevents delamination of tires. If you continue to drive on a low pressure tire it will delaminate.

Use a gimlet, not a twist drill, to clean the hole. A twist drill will cut structural fibres in the tire, something you want to avoid.

 

[Tom.G]

Use a gimlet, not a twist drill, to clean the hole. A twist drill will cut structural fibres in the tire, something you want to avoid.

Hmm, must be different types of Gimlet tools, I've heard it called a 'reamer' or sometimes a 'rasp'.

The cutting action of the gimlet is slightly different from an auger, however, as the end of the screw, and so the initial hole it makes, is smaller; the cutting edges pare away the wood which is moved out by the spiral sides...

(above from: https://en.wikipedia.org/wiki/Gimlet_(tool))

 

[Baluncore]

I took a 1/8" drill bit and using a power drill made a hole thru the tire tread.

A twist drill cuts material ahead as it advances. That is not wanted with the fabric of a tire.

Hmm, must be different types of Gimlet tools, ...

A gimlet has a big handle and is screwed into the material by the tapered screw at the sharp end. Once inserted into the material, a gimlet can be pulled out by the solid handle without needing to be turned backwards.

Some gimlets are designed to cut hardwood from the sides of the hole, but many will just push rubber aside, spreading the fibres sufficiently for a plug to be installed.

 

[jake jot]

It is not the area but the number of long fibres that are disrupted that is important. That is not an area problem, it is a more critical linear problem.

Tire plugs come as either impregnated rope plugs inserted from outside, or as rubber mushroom plugs, that are inserted from the inside, with an integral internal patch. Both should be installed with rubber contact adhesive.

Engine oil, and more particularly diesel fuel, may soften an older dry tire. I would keep both well away from rubber tires. They will modify the friction properties of the rubber on the road. There is no telling what will happen when engine oil is absorbed into the tire fabric. I expect the rubber will become softer and swell which might make a better short term repair. But the last thing you need is to lubricate the internal fibres of the tire where they are bonded to the rubber. Best seal that hole with rubber cement.

When you described "internal fibres of the tire". Did you mean the rubber or belt or plies? which one has fibers in it?Also if a tire is 6 years old already. Some repair centers won't even open up the rim to look inside. They said the sidewall could rupture if the tire is put in a machine press (to open it up) if it is old already. But if there is no visible rupture. Can unseen internal damage occur to 6 years old tire if the technician will try to put patch inside? How about tire that is 2 to 3 years old?

Does this mean every time there is nail puncture in a tire. It must be replaced new?

Water is a natural lubricant for rubber, but it is not a good glue. Once you have a nail part way into a dry tire it may stop there and wear against the road for a while. But when it rains and the tire gets wet, the nail may advance further to complete the puncture.

Internal air pressure prevents delamination of tires. If you continue to drive on a low pressure tire it will delaminate.

Use a gimlet, not a twist drill, to clean the hole. A twist drill will cut structural fibres in the tire, something you want to avoid.

 

[Ranger Mike]

I have drilled and plugged racing slicks successfully over the decades. These tires are light weight thin tread, nylon or steel or kevlar belted race tires. The tire is subject to tremendous lateral forces and tread flex compared to a passenger tire. Once plugged the tire was raced for the duration of its tread life. this applies to round track and left and right turn road course racing. One small hole put in the tire by accident or on purpose is not going to impact the safety of the driver if plugged correctly. if possible use a patch on the inside of the tire. We had a time element and had to plug it to race. We all knew the risk. Is drilling the best way? No, if you have time to patch it, patch it.

 

[Baluncore]

When you described "internal fibres of the tire". Did you mean the rubber or belt or plies? which one has fibers in it?

The belt and the plies, are woven, or cross laid in alternate layers, from long fibres or wire. Those fibres are held in position by the rubber.

Does this mean every time there is nail puncture in a tire. It must be replaced new?

No. If it is a simple puncture through the tread it can usually be plugged.

Old tires dry out and become cracked as the plasticiser is lost. Water and dirt can then contact the fabric and damage the fibres. Fitting and inflating an old tire can be dangerous if you do not know what you are doing and don't stand in a safe place. I have had sidewalls separate from the tread, but only in old cracked tires when I have inflated them very rapidly using an unapproved technique.

Low pressure tires for low speed off-road vehicles such as tractors are less critical than road tires used at high speed on a highway. Many old tractor tires have had the sidewall stitched with copper wire after being staked on a root or branch. It is no longer an approved practice, but it has saved thousands of dollars where the wheel had an inner tube at less than 15 psi, 1 bar or 100 kPa.

I have drilled and plugged racing slicks successfully over the decades.

All I can say is use a gimlet or a screw as the bit, not a twist drill bit. Your repair only has to last less than one race, and there is probably no insurance company involved.

 

[jake jot]

The belt and the plies, are woven, or cross laid in alternate layers, from long fibres or wire. Those fibres are held in position by the rubber.No. If it is a simple puncture through the tread it can usually be plugged.

Old tires dry out and become cracked as the plasticiser is lost. Water and dirt can then contact the fabric and damage the fibres. Fitting and inflating an old tire can be dangerous if you do not know what you are doing and don't stand in a safe place. I have had sidewalls separate from the tread, but only in old cracked tires when I have inflated them very rapidly using an unapproved technique.

Low pressure tires for low speed off-road vehicles such as tractors are less critical than road tires used at high speed on a highway. Many old tractor tires have had the sidewall stitched with copper wire after being staked on a root or branch. It is no longer an approved practice, but it has saved thousands of dollars where the wheel had an inner tube at less than 15 psi, 1 bar or 100 kPa.All I can say is use a gimlet or a screw as the bit, not a twist drill bit. Your repair only has to last less than one race, and there is probably no insurance company involved.

Some tire shops won't open up your tire and use patch repair if it is 6 years old or older due to possible rupture of the sidewall. This is a tire removal and installer machine. Just look at the picture to skip the video

If the tyre was 6 years old from first use and the shop was able to successfully remove and reassemble the tire using the machine with no visible breakage. Could there be unseen cracks in the belt and ply fiber that can't be seen with intact rubber?

How long does plasticizer last in a rubber tread? 6 years or so only?

 

[Ranger Mike]

I forgot to tell about reaming the hole in the tire. I did it but forgot it in above verbiage.
https://knowhow.napaonline.com/how-to-use-a-tire-plug-kit-the-right-way/

 

[Baluncore]

If the tyre was 6 years old from first use and the shop was able to successfully remove and reassemble the tire using the machine with no visible breakage. Could there be unseen cracks in the belt and ply fiber that can't be seen with intact rubber?

It is cracks in the rubber that are the problem because they allow water to contact the tensile fabric inside the tire. When the fabric starts to fail the tire will begin to bulge or distort, so the tire will be difficult to balance.

Unseen damage is always possible, you may have hit a curb. But a tire without cracks is unlikely to deteriorate rapidly, so cracks in the rubber are the best indication of needing "retirement".

How long does plasticizer last in a rubber tread? 6 years or so only?

It will depend on the temperature. I would expect more than 6 years if you are in a cool climate and park the vehicle out of the sun.

 

[jake jot]

It depends on the damage. If the tensile fabric of the tire has been cut, then it can no longer carry the tension, so it must not be repaired with a plug. Since the sidewall of the tire has minimum fabric and maximum flexibility, it must never be plugged.

Normally a spike such as a thorn or a nail will separate the parallel fibres in the fabric, but hopefully not cut them. The fibres can then be separated further as a plug is inserted. The plug is then pinched by the tension in the fabric as the tire is inflated. The glue on the plug will seal the hole in the rubber.

Since inserting a plug will distort the tension in the fabric, plugs must be separated by a minimum of 120° about the tire. That way, two plugs will not place undue load on the same fibre.

In your description above. You didn't mention the reaming part, which is making the hole bigger. They use tool to widen the hole. This is from a video below showing the inside shot.

How many fibers do you think were cut above? 10? 100? This is the complete video showing the inside view at the last parts as well. Notice the initial hole was only nail size but he made it bigger.



If a driver is running a car in the highway, and this plug came out. How long before the air gets out of the tyre and what happens to the car? I'm lookin for some youtube video about this.

It seems plug repair is dangerous unless it is made perfect with full glue and attachment to the tire with minimal fiber damage. But it is difficult to avoid such fiber damage especially since you have ream the hole wider (the purpose of the ream is to make the hole surfaces rough too, isn't it?)

 

[anorlunda]

Do NOT try the method in the video on a tubeless motorcycle tire. The rope plug removes itself in roughly 20 miles (30km)... and that is riding slowly on surface streets.

I'm curious about that. Why is motorcycle tire duty on surface streets different than 4 wheel car tires?

 

[hutchphd]

If a driver is running a car in the highway, and this plug came out. How long before the air gets out of the tyre and what happens to the car? I'm lookin for some youtube video about this.

As was pointed out earlier by @Baluncore the overarching issue is infiltration damage to, and further deterioration of, the cord/belt structure of the tire leading to catastrophic failure.
This was news to me.

 

[Tom.G]

I'm curious about that. Why is motorcycle tire duty on surface streets different than 4 wheel car tires?

Probably because they are so much thinner, less rubber, fewer cord layers, resulting in much less surface area for the rope to bond to.

BTW, this was from an experience after one of the California earthquakes. About a week after the quake, my wife and I hopped on the bike to view the scene of houses shifted off their foundations. We picked up a roofing nail in the rear tire. Fortunately we had a tire repair kit with us, the kind with rope plugs for the tubless tire.

We noticed the instability due to reduced tire pressure and put a plug in, then stopped at the first gas station to add air. (note: gas station employees will NOT touch motorcycle tires.)

We got about half way home (on surface streets) and did a repeat of the above when the plug came out.

Cheers,
Tom

 

[jake jot]

As was pointed out earlier by @Baluncore the overarching issue is infiltration damage to, and further deterioration of, the cord/belt structure of the tire leading to catastrophic failure.
This was news to me.

My question to Baluncore was NOT about slow infiltration damage. Look at this snip from a video in youtube shared in message #17.

I was asking what would happen if a car is moving at say 60 mile per hour and the plug suddenly came out. How long before the tire can go flat? 5 seconds? 30 seconds? And what would happen to such car with a sudden small hole showing up (from the detached plug)? Any videos of such incidents? Tom said in case of motorcycle, the rider would go to grave. But I want to see video of the sequence when it happens to a car.

I also need to know the following. If there was improper plug insertion done and the technician inserted a new plug with glue and everything. And he just pushed the old plug inside due to not wanting to damage the sidewall by putting it in tyre changing machine. What would happen to the old plug (or any light object inside the tyre)? I can imagine it rotating inside, could it somehow centripetal itself to the rim edge causing slow loss of air? What is the guidance about small light debris such as string plug left inside the tyre?

 

[Baluncore]

I was asking what would happen if a car is moving at say 60 mile per hour and the plug suddenly came out. How long before the tire can go flat? 5 seconds? 30 seconds? And what would happen to such car with a sudden small hole showing up (from the detached plug)?

Deflation time is not important since you would not know it was lost until you noticed the lower pressure in the tire. Continuing to drive at speed on a low pressure tire will separate the tread belt from the sidewall fabric, the belt will be thrown off, maybe beating and damaging the bodywork in the process. It is that final catastrophic failure that happens so suddenly, and losing a plug is the least likely cause of such a failure. Plugs are not that dangerous.

But I want to see video of the sequence when it happens to a car.

Youtube “tire blowout”

And he just pushed the old plug inside due to not wanting to damage the sidewall by putting it in tyre changing machine. What would happen to the old plug (or any light object inside the tyre)? I can imagine it rotating inside, could it somehow centripetal itself to the rim edge causing slow loss of air?

The old plug would be thrown centrifugally to the inside tread surface, where it would roll around, collecting dirt and gradually becoming a rubber ball. There are often small balls of dirt and rubber in tyres that accumulate over time. It would not cause a leak because the wire bead of the tire is sealed against the rim, and debris is most unlikely to levitate up to the bead or settle there.

What is the guidance about small light debris such as string plug left inside the tyre?

If there is a guideline it will say don't do it, but I don't think it really matters that much. Heavy vehicles often have half a kilogram of ceramic balancing beads rolling around inside each tire.

 

[jake jot]

Deflation time is not important since you would not know it was lost until you noticed the lower pressure in the tire. Continuing to drive at speed on a low pressure tire will separate the tread belt from the sidewall fabric, the belt will be thrown off, maybe beating and damaging the bodywork in the process. It is that final catastrophic failure that happens so suddenly, and losing a plug is the least likely cause of such a failure. Plugs are not that dangerous.

Have you tried using plug repair before? There is a part called reaming where a tool is inserted to make the nail size hole become three times bigger. This is in order to let in the string plug. So in the event the plugs were ejected during driving (especially improper installation where no glue was used for instance). This can make air in the tire leak within a minute and next thing you know you were driving completely flat (and produced the scenario). So why do you say plugs are not that dangerous?

Are there plug repairs where you don't use any reamer to make the hole bigger to insert the string plug? Maybe you were referring to such plugs that don't make the hole bigger?

Usually what are the distances between fibers in the belts or plies? How many fibers were destroyed when typical reamer (such as below) in string plug repair was inserted (to make the hole bigger). This was from typical instructions in a plug repair kit (I don't have guts to use it, I'd just service centers fix it from inside. But I need to know how many fibers can reamers plug repair kits destroy for reference. Thanks).

Youtube “tire blowout”The old plug would be thrown centrifugally to the inside tread surface, where it would roll around, collecting dirt and gradually becoming a rubber ball. There are often small balls of dirt and rubber in tyres that accumulate over time. It would not cause a leak because the wire bead of the tire is sealed against the rim, and debris is most unlikely to levitate up to the bead or settle there.If there is a guideline it will say don't do it, but I don't think it really matters that much. Heavy vehicles often have half a kilogram of ceramic balancing beads rolling around inside each tire.

 

[Baluncore]

I did not set out to write a complete “theory and practice” of plugging a tire. I try to understand and practice the principles involved. There is plenty of ill informed advice on social media, like the practice of using a twist drill to enlarge the hole. There is something subliminally attractive about the destructive behaviour of drilling a hole in a tire. That will ensure the meme is propagated by the fascinated.

Have you tried using plug repair before?

Yes, but I have tire stripping and fitting equipment, so I do not need to do it very often. Usually it is locals who drop in for a quick tire plug on their way to the city. I strip good wheels and tires from vehicles going to scrap, so I get to see many other's repairs and plugs.

There is a part called reaming where a tool is inserted to make the nail size hole become three times bigger. This is in order to let in the string plug.

A tire is a mesh of fibres in tension, all held together, encased and protected by rubber. The aim of the reaming process is to prepare a clean hole sufficiently large only to insert the plug with the tool provided.
The original puncture hole may have a wet or oil contaminated surface that will not bond with the plug. It may have radiating cracks that will not fill with cement and so will continue to slowly leak air. It may also have flakes of rust or embedded grit that will allow air past the plug, now or at a later date.
The aim of reaming is to remove contamination and radial cracks, while avoiding damage to the fibres. A “reamer” will remove crumbs of rubber from around the fibers without cutting the fibres. A sharp twist drill is bad because it will cut the fibres while removing the rubber.
If fibres were cut with a drill, then inflation of the tire would pull the cut fibre ends back from the hole, which would reduce the seal and release the plug. If fibres remain intact, but deviate around the plug, when the tire is inflated they will tighten to hold the plug in place.

So why do you say plugs are not that dangerous?

There are much more likely ways to get a puncture and blowout than by the extremely rare loss of a plug. It is not the plug, but an uninformed operator who is dangerous. That danger is more to the value of the tire, which can be destroyed by careless plugging. If when tested after repair, a plug glued into a correctly reamed hole holds air, I would expect it to be secure for the life of the original tire.
The plugging trick that takes practice (on an old tire) is turning the tool after insertion, so that a lump is formed on the inside during withdrawal of the tool. That mushroom will help prevent the plug from being pulled out too easily.

Usually what are the distances between fibers in the belts or plies? How many fibers were destroyed when typical reamer (such as below) in string plug repair was inserted (to make the hole bigger).

The size and distance between the fibres varies and is unimportant since they will be laid close, side by side, and the reaming process should separate, not cut the fibres.

I put some air in a neighbours ride-on lawn mower tire yesterday. The reason I smiled was because the low-pressure tire had many plugs, with 5 being in a 2”x2” area. That is what box thorns do.
The reason I had to smile a second time was when I realized the tire still had an inner tube.
I will find out what is really going on when I get to replace those tires.

 

[jake jot]

I did not set out to write a complete “theory and practice” of plugging a tire. I try to understand and practice the principles involved. There is plenty of ill informed advice on social media, like the practice of using a twist drill to enlarge the hole. There is something subliminally attractive about the destructive behaviour of drilling a hole in a tire. That will ensure the meme is propagated by the fascinated.


Yes, but I have tire stripping and fitting equipment, so I do not need to do it very often. Usually it is locals who drop in for a quick tire plug on their way to the city. I strip good wheels and tires from vehicles going to scrap, so I get to see many other's repairs and plugs.


A tire is a mesh of fibres in tension, all held together, encased and protected by rubber. The aim of the reaming process is to prepare a clean hole sufficiently large only to insert the plug with the tool provided.
The original puncture hole may have a wet or oil contaminated surface that will not bond with the plug. It may have radiating cracks that will not fill with cement and so will continue to slowly leak air. It may also have flakes of rust or embedded grit that will allow air past the plug, now or at a later date.
The aim of reaming is to remove contamination and radial cracks, while avoiding damage to the fibres. A “reamer” will remove crumbs of rubber from around the fibers without cutting the fibres. A sharp twist drill is bad because it will cut the fibres while removing the rubber.
If fibres were cut with a drill, then inflation of the tire would pull the cut fibre ends back from the hole, which would reduce the seal and release the plug. If fibres remain intact, but deviate around the plug, when the tire is inflated they will tighten to hold the plug in place.


There are much more likely ways to get a puncture and blowout than by the extremely rare loss of a plug. It is not the plug, but an uninformed operator who is dangerous. That danger is more to the value of the tire, which can be destroyed by careless plugging. If when tested after repair, a plug glued into a correctly reamed hole holds air, I would expect it to be secure for the life of the original tire.
The plugging trick that takes practice (on an old tire) is turning the tool after insertion, so that a lump is formed on the inside during withdrawal of the tool. That mushroom will help prevent the plug from being pulled out too easily.


The size and distance between the fibres varies and is unimportant since they will be laid close, side by side, and the reaming process should separate, not cut the fibres.

I put some air in a neighbours ride-on lawn mower tire yesterday. The reason I smiled was because the low-pressure tire had many plugs, with 5 being in a 2”x2” area. That is what box thorns do.
The reason I had to smile a second time was when I realized the tire still had an inner tube.
I will find out what is really going on when I get to replace those tires.

I talked to the technician who repaired my tire. They used power steering fluid (not engine oil) to insert the string plug in the tire. What do you think is the interaction of engine oil to the tire? He said the reason he had to use oil was because he didn't have a reamer tool so use pointed screw driver to puncture the hole. This is the screw that punctured the tire.

A pointed driver was stabbed to the small hole to make it a big bigger. But I guess it only punctured the belt and fly and didn't remove the rubber. Do you think a pointed driver would cut the fibers in the belt/ply?

He said he used Permacure adhesive to insert the plug. But had to use power steering fluid to insert it.

Anyway. The tire is already 6 years old this week. I'll replace all 4 tires with new ones. But need the above information about the interaction of power steering fuid in the hole with the rubber/belt/play and other adhesive. If adhesive is used. Do you think the plug can eject out with the steering fluid present?

Thanks a lot!

 

[Baluncore]

They used power steering fluid (not engine oil) to insert the string plug in the tire. What do you think is the interaction of engine oil to the tire?

Engine oil is a mineral lubricating oil. It will soak into the rubber and reduce friction properties. It may change the bonding of the rubber and cause it to become soft and swollen. It may break adhesion between the fibre and the rubber.
Power steering fluid is usually the same as automatic transmission fluid, ATF. It is a different type of oil, originally with a vegetable base that does not damage rubber. ATF is less of a problem with tire rubber than is engine oil.

He said the reason he had to use oil was because he didn't have a reamer tool so use pointed screw driver to puncture the hole.

I guess the screwdriver would remain tight in a dry hole, so ATF was used as a lubricant. The problem is compounded, beyond using the wrong tool. The hole is not enlarged, while it is further contaminated.
Your technician does not understand why he is doing things, so says what sounds good with confidence, assuming that you will be unable to analyse it. That is very common in trades without theory or analysis, where the apprentice blindly follows the master. It can be interesting watching a traditional practice, while trying to work out why it is done that way. Caution is necessary before changing a practice. There are so many possible hidden implications that it is a real challenge to work out a better way, without making things worse.

Do you think a pointed driver would cut the fibers in the belt/ply?

Probably not. It would force the fibres apart while compressing the rubber, then it would all spring back to where it started.
I expect a threaded rod or bolt, filed or ground to a tapered point, would make a better reamer than a cross-point screwdriver.

He said he used Permacure adhesive to insert the plug. But had to use power steering fluid to insert it.

I assume Permacure adhesive is a rubber cement. Mixing it with ATF will produce a slow drying glue that is thick enough to seal the plug in the unprepared hole.
First the solvent in the rubber cement will immediately evaporate. Then the ATF will diffuse away through the rubber while the tire is hot and flexing. Some ATF will be wiped off on the road. The remaining rubber and ATF mix will seal the hole.

If adhesive is used. Do you think the plug can eject out with the steering fluid present?

It is certainly bad practice, but I think the technician will get away with it most of the time. That is why his practice continues. Because it still seems to work for him.

Tire plugs would have been prohibited if they were not so very tolerant to bad practices.

 

[jake jot]

Engine oil is a mineral lubricating oil. It will soak into the rubber and reduce friction properties. It may change the bonding of the rubber and cause it to become soft and swollen. It may break adhesion between the fibre and the rubber.
Power steering fluid is usually the same as automatic transmission fluid, ATF. It is a different type of oil, originally with a vegetable base that does not damage rubber. ATF is less of a problem with tire rubber than is engine oil.I guess the screwdriver would remain tight in a dry hole, so ATF was used as a lubricant. The problem is compounded, beyond using the wrong tool. The hole is not enlarged, while it is further contaminated.
Your technician does not understand why he is doing things, so says what sounds good with confidence, assuming that you will be unable to analyse it. That is very common in trades without theory or analysis, where the apprentice blindly follows the master. It can be interesting watching a traditional practice, while trying to work out why it is done that way. Caution is necessary before changing a practice. There are so many possible hidden implications that it is a real challenge to work out a better way, without making things worse.Probably not. It would force the fibres apart while compressing the rubber, then it would all spring back to where it started.
I expect a threaded rod or bolt, filed or ground to a tapered point, would make a better reamer than a cross-point screwdriver.I assume Permacure adhesive is a rubber cement. Mixing it with ATF will produce a slow drying glue that is thick enough to seal the plug in the unprepared hole.
First the solvent in the rubber cement will immediately evaporate. Then the ATF will diffuse away through the rubber while the tire is hot and flexing. Some ATF will be wiped off on the road. The remaining rubber and ATF mix will seal the hole.It is certainly bad practice, but I think the technician will get away with it most of the time. That is why his practice continues. Because it still seems to work for him.

Tire plugs would have been prohibited if they were not so very tolerant to bad practices.

I went back to the service center to ask what exactly the oil used and if they really used any adhesive or not. The technicians who did them confirmed ATF (Automatic Transmission Fluid used) was put and no adhesive was used because they didn't stock any. So I told them to buy a bottle of adhesive so they can re do the plugging.

This is the adhesive they bought (a Contact Cement instead of Rubber Cement. It's written "Premium Contact Cement" below the label Rugby)

I asked them what exact plug they used. They showed me these.

Back of box.

This is showing the inside of it.

First question. Does the above plug have built in sealant? The technician it seemed to have sticky something so he didn't use adhesive because he believed it has built in adhesive. True?

Anyway I told him to remove the plug and put new plug with rubber cement used and not put any ATF.

This is the attempt at removal of the plug (please note if the hole is damaged further and what kind of damages).



These are when the new plugs were inserted with the contact cement applied (but he didn't wait 15 mins for the contact cement to dry. Won't it remain liquid inside? But perhaps the air pressure inside can dry the contact cement instantly bonded?)



What is your comment about the removal of the old plugs and insertion of the new plug? What kinds of damages may it have caused to the spot/hole? I'll replace all tires with new since they are 6 years old already. But when I throw away the old tires. People always picked them up and resell to others so I need to know whether to destroy the tire so it can't be re used (if the re insertion of new plug damaged the hole and non usable anymore).

Thank you.

 

[jake jot]

I went back to the service center to ask what exactly the oil used and if they really used any adhesive or not. The technicians who did them confirmed ATF (Automatic Transmission Fluid used) was put and no adhesive was used because they didn't stock any. So I told them to buy a bottle of adhesive so they can re do the plugging.

This is the adhesive they bought (a Contact Cement instead of Rubber Cement. It's written "Premium Contact Cement" below the label Rugby)

View attachment 295078

I asked them what exact plug they used. They showed me these.

View attachment 295069

Back of box.View attachment 295072

This is showing the inside of it.

View attachment 295071

View attachment 295070

First question. Does the above plug have built in sealant? The technician it seemed to have sticky something so he didn't use adhesive because he believed it has built in adhesive. True?

Anyway I told him to remove the plug and put new plug with rubber cement used and not put any ATF.

This is the attempt at removal of the plug (please note if the hole is damaged further and what kind of damages).



These are when the new plugs were inserted with the contact cement applied (but he didn't wait 15 mins for the contact cement to dry. Won't it remain liquid inside? But perhaps the air pressure inside can dry the contact cement instantly bonded?)



What is your comment about the removal of the old plugs and insertion of the new plug? What kinds of damages may it have caused to the spot/hole? I'll replace all tires with new since they are 6 years old already. But when I throw away the old tires. People always picked them up and resell to others so I need to know whether to destroy the tire so it can't be re used (if the re insertion of new plug damaged the hole and non usable anymore).

Thank you.

I edited the above the emphasized the fact they used contact cement instead of rubber cement. But they didn't wait for 15 minutes and letting the contact cement dry first before inserting the string plug. They inserted it right away. So I wonder whether the thick contact cement inserted would remain wet inside the tire, or would it evaporate too inside leaving surfaces with cement but not binded? I imagine with 32 psi of air inside, this can evaporate the contact cement but where will it evaporate to? Perhaps just circling it inside the tire?

I'll get new tires from a tire shop and may not give the old repaired tire to them in case they sell it to someone.

 

[Tom.G]

If you keep the tire with the plug you then have the perfect opportunity to cut it apart and find out exactly how well the plug bonded.

PLEASE let us know what you find!

Cheers,
Tom

 

[jake jot]

If you keep the tire with the plug you then have the perfect opportunity to cut it apart and find out exactly how well the plug bonded.

PLEASE let us know what you find!

Cheers,
Tom

I went to a tire shop to change all 4 tires because the car is AWD and you must have uniform thread wear in all tires or the drive train can be affected. I didn't trust the string plug repair method used.

I went to look at inside the tire which was string plugged twice. Remember

1. During initial plug, the technician (from another shop) used ATF fluid and insert just plain driver and not reamer so the hole is smaller.

2. During second repair plug, the technician (also from that another shop) put contact cement with the string plug. As you know, contact cement needs to be dried 15 mins before touching them. He didn't use rubber cement.

I took video of what the inside of the tire looked like:



It's like spaghettization from the black hole (maybe it is). There is no binding of the contact cement immediately inserted.

This is zoom of it.

This is size of it:

This is how the string plugged is supposed to be pulled (near the end of the youtube video below it).





So is this supposed to be how every string plug need to be pulled, ending with 4 strings total inside the hole?? Or does some do 2 insertions do?

Of course I don't trust it, that's why I had 4 new tires installed (for one bad string patch repair).

In my place we mostly used patch inside for nail puncture and just leave the hole outside unplugged. It's very small so they never bother to widen it and put any plug. But could some kind of sealant be used for small nail size puncture hole (from the external) with patch repair done inside?

Lastly, do they used vulcanization solution or just plain rubber cement in string plug repair? As you will read a chemist described below. Vulcanization solution can bind the rubber string plug and tire rubber as one!



"Chemist here - natural rubber is a polymer (long chain-like molecules). Vulcanizing adds cross-links (through disulfide bonds) to the rubber, basically turning the strands of rubber molecules into a net, greatly increasing strength. Bike tubes are vulcanized rubber, but the outer surfaces are treated such that all those cross-linking sulfur groups aren't reaching out and trying to grab anything. You put on some vulcanizing fluid (henceforth "glue") and a few disulfide bonds in the tube get broken and re-formed with bonds to the polymers in the glue. Once the glue dries (there's a bit of solvent that has to evaporate) the inner side of the glue spot is chemically bound to the tire. The outer side is left with a bunch of free sulfur groups waiting to grab onto some other sulfur groups. Then you peel that piece of foil off the orange side of the tire patch (which exposes the free sulfur groups left on the patch) and press it to the glue spot - you've now made millions of chemical bonds between the patch and the glue spot. It's not really glued, though - the patch-"glue"-tire system is now one single molecule all chemically bound together.

The chemical bond holding things together is why:

The tube has to be clean and dry - the sulfur groups reaching out for something to grab onto will grab dirt, water, and other gunk instead of the patch.

You can't use duct tape or regular glue - these are sticky substances that don't vulcanize the rubber together. Rubber cement may hold a patch in place but it is NOT the same stuff.

Glueless patches kinda suck - the vulcanizing fluid in the little tubes works better at making bonds with the punctured bike tube.

You can make patches out of old tubes - at its most basic you're vulcanizing two pieces of rubber together, so two pieces of bike tube will stick to each other."

(Ping Baluncore and other Tire experts). Thanks!