Independent, impartial advice for car buyers and car owners

Find an Expert Rating: 

What sort of tyre sidewall damage is dangerous?

We breakdown which types of tyre sidewall damage is acceptable and dangerous, and what would fail an MOT inspection

Our Expert Partners

Looking for car tyres? Check out the latest offers from our commercial partners below.
MotorEasy logo 300x150

Tyres, warranty, GAP and servicing from MotorEasy
Find out more

Kwik Fit logo

For tyres, brakes, MOT, exhausts and car services you can trust
Find out more

ebay logo 600x300

Shop car tyres with installation
Find out more

Tyre Shopper logo 360x180px

The UK's No. 1 online cheap tyre retailer – guaranteed
Find out more

Tyre Pros logo 2022

Cheap tyres in your local area
Find out more

My Tyres logo 392x196px

Europe’s biggest online tyre retailer
Find out more


The sides – or sidewalls – of car tyres have a tough job, supporting the weight of the car, flexing against kerbs and speed bumps and absorbing the impact from potholes while keeping the tyre sealed to the wheel rim.

They’re strengthened for these ordeals, but can still pick up cuts, cracks and bulges. Ignoring such damage increases the risk of tyre failure at some point in the future, possibly disintegration of the sidewall and a blowout.

As you’re advised to regularly look over the tyre tread for wear, this is also the time to get a look at the sidewall. Remember to check the inside of the tread/sidewall as well. Where it’s safe to do so, lie on your back and use a torch to help you.

How to check for sidewall damage

A tyre sidewall is not always perfectly even; sometimes there will be dimples and indentations. Indentations are harmless and aren’t detrimental to either driving or safety characteristics. The dimples are superficial. You’re looking for bulges and splits.

At the MOT test, as well as checking for the minimum legal tread depth across at least ¾ of the width of the tyre (1.6mm) tyres are also expected for visible damage.

For cuts, the government’s vehicle inspection manual advises testers to fail if any ply or cord (the inner construction of the tyre) can be seen without touching the tyre or it can be seen by folding back rubber or opening a cut with a blunt instrument.

When assessing lumps or bulges testers are advised to distinguish between normal undulations resulting from manufacturing, and lumps or bulges caused by structural deterioration.

A pronounced external bulge on the sidewall of the tyre indicates that strengthening cords inside have been destroyed within the carcass. This is a fail and will need replacement.

When you’re checking the sidewall, continue over the top to the tread and look for objects such as nails or glass sticking out of the tyre. You can expect some pieces of gravel to lodge between the treads, but sharp stones can also lead to a slow puncture.

Read more:

Latest car tyre features and advice

Russell Hayes
Russell Hayeshttps://amzn.to/3dga7y8
Russell Hayes’ early career was 14 years of motoring journalism in print, television and online. He worked for What Car? and Complete Car magazines, the BBC's original Top Gear programme and Channel 4's Driven. Since 2007 he has written motoring history books on subjects including Lotus, TVR, the Earls Court Motor Show, the Volkswagen Golf, Volkswagen Beetle and Bus and the original Aston Martin V8. Now a full-time author, two more books are in the pipeline for 2023 and 2024.