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What is a string plug repair?
A string plug repair involves inserting into the hole, from the outside, a cord of special rubber that fills and seals it. A tool is used that first cleans and sizes the hole and then pushes the string inside.
The advantage is speed: in many cases the tyre doesn't need to be removed from the rim. The drawback is that you can't see the inside of the tyre, so any damage caused by the foreign object or by driving on low pressure can remain hidden.
What is a mushroom patch repair?
A mushroom patch repair is carried out from the inside: the tyre is removed from the rim, the inside is inspected and prepared, and a mushroom-shaped insert is applied. The stem fills the hole and the head seals the inner surface.
The key step is the internal inspection: with the tyre off, the technician can see whether there are signs of driving on low pressure, damaged plies or other holes, and can decide whether a repair is really possible.
Mushroom patch and string plug compared
The mushroom patch and string plug differ mainly in how they're applied and whether the inside of the tyre can be checked.
| String plug | Mushroom patch | |
|---|---|---|
| Application | From the outside | From the inside |
| Tyre removal | Generally not needed | Needed |
| Internal inspection | No | Yes |
| Sealing of the inner surface | No | Yes |
| Typical use | Quick or temporary fix | Repair generally considered more complete |
Which repair is better?
In general, a repair from the inside with a mushroom patch, preceded by an inspection of the removed tyre, is considered the most complete, because it combines filling the hole with sealing the inside and checking for hidden damage.
A string plug can be a valid solution in specific situations, for example to get a vehicle back on the road quickly. In any case the choice rests with the technician, who assesses the damage, the type of tyre and the manufacturer's instructions.
When is neither a mushroom patch nor a string plug possible?
Neither a mushroom patch nor a string plug is possible when the damage isn't a small hole in the tread. The following generally can't be repaired:
- damage on the shoulder or sidewall;
- long cuts or tears (see cut tyre);
- bulges on the sidewall;
- visible plies;
- tyres that have been driven a long way while flat.
Find out more in when can a tyre be repaired.
On-the-spot repair in Milan?
In Milan and the surrounding province SOS Tyre comes out 24/7, in 30 minutes on average, to wherever the vehicle is and, when technically possible, repairs the tyre on the spot. Find out how our on-the-spot tyre repair works or call +39 377 326 0999.
Frequently asked questions
Is a string plug a permanent repair?
It depends on the case and the technician's assessment. Many professionals consider it a temporary fix, because it doesn't allow the inside of the tyre to be inspected. If you've had a string plug repair, it's sensible to have the tyre removed and checked at the first opportunity.
Can you see a mushroom patch from the outside of the tyre?
Usually all you can see from the outside is a small mark where the hole was, because the stem of the patch fills it and is trimmed flush with the tread. The main part of the repair, the head of the patch, stays inside the tyre.
Is wheel balancing needed after a mushroom patch repair?
Generally yes: when the tyre is removed and refitted on the rim it's good practice to rebalance the wheel, to avoid vibrations while driving. The technician assesses each case based on the work carried out.
Can a mushroom patch be fitted to a tyre already repaired with a string plug?
In some cases yes: the technician removes the tyre, removes or trims the string and assesses whether to apply a repair from the inside. The decision depends on the condition of the hole and the internal inspection, which may also reveal damage that can't be repaired.