Emergency Tire Repair using Gummy Worm Patch

Emergency Tire Repair
There are two schools of thought on tire repair. One advises that you should never ever attempt to repair a tire, and you should never attempt to drive on a repair. (If you belong to this school of thought, why are you reading this tutorial?). The other acknowledges that a flat will not always happen when convenient, and it can be prudent to attempt a repair. Needless to say, those who sell tires will usually suggest the former, whereas realists will acknowledge the latter. If you chose to patch a tire to repair a leak, you do so at your own risk.

If the damage is relatively minor and you get a good patch, some people will tell you that the patch will be good for the life of a tire.

Tip: You should never patch the sidewall of a tire - the sidewalls are subject to stresses very different than the flat of the tire, and riding on a sidewall patch can result in a blowout.

Recently I had a flat front tire that necessitated emergency repair. Unfortunately the repair facilitated on the road had a slow leak which proved to be a nightmare to ride with. In the hopes that I can save one person from making the same mistake and the subsequent hassle of riding on a questionable patch, I used my old tire to put together this tutorial.

Obviously you will be patching the tire on the bike, but I am using the old tire that is ready to be disposed of to illustrate the technique.

You will need:
Gummy String style tire plug
Tire plug applicator
Multi-tool (or tire plug rasp)
Air to inflate (air compressor, CO2 canister (these are sold at any bike tire for one-time inflation use).

(It's a good idea to travel with these tools, as you can never predict when a puncture will happen. You might be able to find a passing motorist with an air compressor, but that motorist is very unlikely to be carrying a patch tool or gummy string. Besides, if you are well equipped, you will be able to help out another stranded motorcyclist on the road and make a new friend).

Ok, you have a flat… now what?

Locate the source of the leak
Inspect your tire and try to locate the source of the leak. If you are unsure, use water (or spit) on the tire to see if the tire pressure is causing it to bubble.


Enlarge Hole in Tire
You may need to enlarge the hole slightly so that you can insert the patch tool. Your tire patch kit may have a small burred reamer to enlarge the hole (this is obviously the best candidate). Alternatively, the small screwdriver attachment on a multi-tool will work well for this (don't use a knife). Be cautious not to tear a huge gaping hole in your tire - you only want to enlarge the hole so that you can just insert the tire tool into the tire. You do not want to inflict additional damage to the tire. (Test fit the tire tool into the hole and err on the side of caution. You can always enlarge the hole, but if your hole is too large, you may be unable to successfully patch it).



Carefully enlarging hole in tire


Check Tire Tool
Your tire tool has a slit at the bottom to allow it to release the gummy string inside the tire. If you are using a cheap tire tool, you might want to bend the metal slightly so that it will release the worm inside your tire.

The photo below shows a multi-tool being used to bend the eye of the insertion tool slightly. When pressed into the tire, the tips of the tool will still come together.



Fixing cheap tire tool so that it can let go of gummy string inside of tire

Insert Gummy String
Insert the gummy string into the applicator so that it is centered.


Gummy string centered in applicator

Insert String into Tire
Insert the tool holding the gummy string into the tire. It will slide in easily until you reach the gummy string which will add a bit of resistance.


Starting to insert string into tire


You may need to rotate the tool slightly to work the tool into the tire.
The gummy string will add resistance



You will want to insert the tool until the handle reaches the tire, and you only have the two tails of the patch hanging out. If you do not have at least half the string inside the tire, you may not have enough to patch the tire.


Insert the string as far as possible into the tire

Here you can see the tool holding the gummy string inside the tire. Note that the prongs are slightly separated so that the tool will release the string when it is removed.


Tool holding gummy string inside tire

Removal of Tool
Remove the applicator tool from the tire by rotating side to side and pulling straight out. A twisting motion will help the string ball up inside the tire. The hoop of the gummy string should be left inside the tire.

Warning: If the hoop of the gummy string comes out of the tire, you will not have a successful patch. If this happens, pull the string all the way out of the tire and try again (check to ensure that your tool will release the string - if you are using a cheap tool, revisit the third step of this tutorial).

Once you have removed the tool, you will have two short ends of the string hanging outside the tire. Give a gentle tug on these to make sure that the patch feels secure.


Short tails hanging out of tire


Inflate Tire and Trim Strings
Inflate your tire. Trim the ends of the string close to the tire using a knife and a gentle sawing motion. (If you have a successful plug, you can put a bit of tension on these strings to cut them).


Trimming the string

A Successful Patch
A successful patch leaves enough of the gummy string inside the tire to ball up and plug the hole from the inside. When you fill the tire with air, the air pressure will force the patch against the wall of the tire.

Here's a look at the patch from the inside of the tire. Note how nicely the patch balls up to provide an effective plug.


Successful patch from inside of tire

An easy way to check your patch is to use some water (or spit) to ensure that the patch is not bubbling or allowing an air leak.

If your patch is allowing air to escape the likely candidates are:
- You are patching a hole that is too large (or you enlarged the hole too much in step 2)
- You do not have enough of the patch inside the tire
- You may have a second leak in the tire

After the Patch
After patching the tire, common sense suggests that it is a good idea to drive cautiously and stop regularly to check that your tire is still holding correct air pressure.

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Lessons Learned from a Bad Patch...
On my recent tire outage experience, my patch had a slow leak. I opted to ride on the questionable patch at a greatly reduced speed and stopping frequently to check and reinflate the tire. This is not recommended, and made for a very stressful riding experience.

When my tire was patched the gummy string came back out of the hole with the tool. At the time I was not aware that this was not supposed to happen. This did not leave enough of the string inside to form an adequate plug. (I believe that this was related to the fact that I had a very cheap tire tool that did not release the string - I had to pry it open to get it to work for this tutorial). The photo below shows that there is inadequate plug material inside the tire. You can also see tire damage to the side of the plug.


Inadequate plug material inside tire - hoop of string did not remain in tire

Additionally, I believe that the hole was enlarged too much to allow the tool to enter the tire. This meant that we were plugging a hole that was too large for the patch. You can see the hole on the photo below.


Hole from inside showing too much damage to patch


Hole from outside showing too much damage to patch

I believe that when the hole was enlarged that the person doing the patch used a knife to enlarge the hole rather than the small screwdriver on the multi-tool, and introduced too much new damage to the tire for a successful patch. (Lesson learned: no matter how hard you are shaking, always patch your own tire.).