Tire Sidewall Damage Chart 2026: Cracks, Cuts and Bulges

Most sidewall marks fall into two groups. Hairline cracks and kerb scuffs that stay in the outer rubber are usually cosmetic; a bulge, a cut or crack that reaches the cords, or a hole below the shoulder means the tyre is finished, because the sidewall carries the load and flexes on every turn of the wheel. The chart below sorts eight common findings by what you can see, whether the car is safe to drive, and what a fitter will do.

Tire sidewall damage chart

The one test that settles most cases: if anything other than black rubber shows - fabric, white, yellow or metal threads - or the rubber stands proud in one spot, the tyre’s structure is damaged and it has to be replaced.

Sidewall damage — repair or replace? The quick answer

Almost always replace: unlike a tread puncture, sidewall damage cannot be safely repaired. The sidewall is the flexing structural core, so a cut, deep gouge, crack that reaches the cords, or a bulge means the tyre can blow out without warning. A bulge — usually from a pothole or kerb strike — is an immediate replacement. Only the shallowest cosmetic scuffs are safe to leave. The four main damage types are explained one by one below.

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Understanding the Tyre Sidewall

The sidewall runs from the bead (where the tyre seats on the wheel rim) to the shoulder (where it meets the tread). It consists of:

• Rubber compound — the outer protective layer you see
• Carcass plies — layers of nylon or polyester cords that give the tyre its shape and strength
• Inner liner — an airtight rubber layer that holds air pressure

Unlike the tread area, which has multiple steel belt layers for puncture resistance, the sidewall relies primarily on the carcass plies. This makes it more susceptible to damage and essentially impossible to repair reliably.

Types of Sidewall Damage

1. Cuts and Gashes

Cuts are caused by sharp objects — glass, metal debris, sharp kerb edges, or road hazards. The severity depends entirely on depth.

Depth in millimetres is not a reliable guide on its own: sidewall rubber thickness varies by tyre, and Michelin notes that the same object can also cut the inner sidewall, which you cannot see with the wheel on the car. UK MOT testers use the cord test - they open a cut with a blunt instrument and fail the tyre if cords are visible, or if the cut is longer than 25 mm (or 10% of the section width) and the cords can be felt.

A cut that has exposed the internal cords has compromised the structural integrity. Even if the tyre is not losing air, it can fail catastrophically under load or at speed.

2. Bulges and Blisters

A bulge is a raised area on the sidewall, typically egg-shaped or circular. It is caused by internal structural failure — the carcass plies have broken, and air pressure is pushing the rubber outward.

Bulges are always dangerous. There is no safe bulge. A tyre with a sidewall bulge can blow out at any time, particularly at higher speeds or when hitting bumps.

Common causes:

• Hitting a pothole at speed
• Mounting a kerb too fast or at a sharp angle
• Manufacturing defects (rare but possible)
• Driving on an under-inflated tyre

Action: Replace the tyre. If you find a bulge while parked, fit the spare rather than driving to the tyre shop on it. Michelin also notes that an unusual vibration after a pothole can be the first sign of a bulge you have not yet seen.

3. Cracks and Weather Checking

Cracking on the sidewall surface is common in older tyres and those exposed to UV light, ozone, and extreme temperatures. This is called weather checking or ozone cracking.

Minor cracking — shallow surface lines that do not expose any internal material — is cosmetic at first, but Michelin treats any sidewall cracking as a sign the tyre is nearing the end of its life and advises a professional check. Tyre-shine products that strip the rubber’s protective agents can bring cracking on sooner.

Severe cracking — deep fissures, cracking that reveals coloured material underneath the black rubber, or cracks accompanied by hardening of the rubber — indicates the tyre is reaching the end of its safe life.

For guidance on tyre age limits, see our tyre age replacement guide.

4. Scrapes and Kerb Rash

Kerb rash — scuffing from contact with kerbs during parking — is the most common form of sidewall damage. The good news is that it is usually cosmetic.

Cosmetic kerb rash looks like a roughened or lighter-coloured patch on the sidewall. The rubber is abraded but not deeply cut. This does not affect tyre performance.

Severe kerb damage involves chunks of rubber removed, deep gouging, or scraping that has worn through to the cords. This is structural damage and requires replacement.

Legal Requirements

Tyre sidewall condition is part of vehicle roadworthiness inspections in most countries:

• United Kingdom — Regulation 27 of the Road Vehicles (Construction and Use) Regulations 1986 makes it an offence to use a tyre with a cut longer than 25 mm or 10% of the section width (whichever is greater) that is deep enough to reach the ply or cord, any lump, bulge or tear caused by structural failure, or any ply or cord exposed. In the MOT, a cut to the cords is a “major” defect and a bulge or exposed cord is “dangerous”.
• Germany — The periodic inspection (HU) checks tyre condition; a damaged sidewall is a defect.
• France — The contrôle technique inspects tyre condition, including the sidewalls.

Check your country’s specific tyre laws on our tyre laws directory.

Why Sidewall Repairs Are Not Recommended

Unlike tread punctures, which can be permanently repaired with a combination plug-patch, sidewall repairs are ruled out by the US Tire Manufacturers Association (repairs are limited to the tread area) and by Michelin for cuts and tears; Michelin’s only allowance is a hole of 3 mm or less on a tyre rated T or lower. The reasons are:

1. Constant flexing — the sidewall flexes with every wheel revolution. A repair that might hold on the rigid tread will fatigue and fail on the flexible sidewall.
2. Load bearing — the sidewall carries the vehicle’s weight. A weakened area concentrates stress and is prone to blowout.
3. No reinforcement — the tread has steel belts that support repairs. The sidewall has only thin carcass plies.
4. Hidden damage — a fitter cannot confirm from outside that the plies around the injury are intact, so most shops will not take the risk.

For repairable tread punctures, see our puncture repair vs replace guide.

Prevention Tips

Reduce the risk of sidewall damage:

1. Maintain correct tyre pressure — under-inflated tyres have weaker sidewalls and are more susceptible to impact damage. Check pressure monthly using our tyre pressure guide.
2. Avoid potholes and debris — scan the road ahead and steer around hazards where safe.
3. Be careful when parking — approach kerbs slowly and at a shallow angle. Use parking sensors or cameras.
4. Avoid overloading — excess weight puts additional stress on sidewalls. Check your tyre’s load index using our tyre load index guide.
5. Park in shade when possible — UV exposure accelerates rubber degradation and cracking.
6. Watch the tyre’s age — Michelin advises a professional check at least once a year from 5 years of use and replacement at 10 years from manufacture, spare included. Our tyre age guide shows how to read the date code.

What to Do If You Find Sidewall Damage

1. Find your case in the damage chart at the top of this page.
2. If it is a bulge, cord damage or a hole — fit the spare or call roadside assistance rather than driving on the tyre.
3. If moderate — book a professional inspection within 24-48 hours. The tyre may need to be removed from the rim for internal inspection.
4. If cosmetic — monitor the area. Check weekly for any progression — cracks deepening, cuts widening, or bulges developing.
5. When replacing — always replace with the correct size. Use our tyre size calculator to confirm your fitment.

Conclusion

Sidewall damage ranges from harmless cosmetic scuffs to life-threatening structural failures. The critical distinction is depth — if damage has penetrated beyond the surface rubber to expose internal cords, the tyre must be replaced without hesitation. Bulges are always an emergency, regardless of size. For the other sidewall markings - size, load index and speed rating - see our speed ratings explainer and load index guide.

When in doubt, have a professional inspect the tyre by removing it from the rim. The cost of an inspection is trivial compared to the consequences of a sidewall blowout at motorway speeds. For comprehensive tyre regulations in your country, visit our tyre laws directory, and for related tyre care advice, explore our tyre rotation and alignment guide.

Disclaimer: This guide provides general information. Always consult a qualified tyre professional for assessment of specific damage. Tyre safety regulations vary by country — check your local laws before making repair or replacement decisions.