On this page
- What does low-profile tyre mean?
- Why are low-profile tyres more exposed to damage?
- What is the most common damage?
- How do you protect low-profile tyres and wheels?
- Are low-profile tyres often run-flats?
- Can you fit larger wheels than the original ones?
- Puncture on large wheels in Milan?
- Frequently asked questions
What does low-profile tyre mean?
A low-profile tyre has a short sidewall relative to its width, in other words a low aspect ratio (height-to-width ratio). In the size 225/40 R18, for example, the 40 means the sidewall height is 40% of the width.
The meaning of every figure is explained in how to read your tyre size.
Why are low-profile tyres more exposed to damage?
Low-profile tyres are more exposed because there is less room between the edge of the wheel and the road. In an impact the sidewall compresses to its limit and the force reaches the internal structure and the wheel more easily.
- the sidewall can be pinched between the obstacle and the wheel, breaking the internal plies and forming a bulge;
- the rim edge can bend or crack;
- the wheel gets scuffed more easily against kerbs when parking.
What is the most common damage?
The most common damage on low-profile tyres is sidewall bulges, bent wheels and cuts on the shoulder. Much of this damage cannot be repaired and requires the tyre to be replaced.
| Damage | Typical cause | Generally |
|---|---|---|
| Bulge on the sidewall | Pothole or kerb hit hard | Tyre needs replacing |
| Bent wheel | Pothole, raised drain cover | Have it assessed |
| Cut on the shoulder | Sharp edges, kerbs | Cannot be repaired |
| Scuffed wheel | Parking tight against the kerb | Often only cosmetic |
For the signs of a damaged wheel, read the guide on bent or cracked wheels.
How do you protect low-profile tyres and wheels?
To protect them, the most important thing is to keep the pressure recommended by the manufacturer: an under-inflated low-profile tyre has even less margin before the wheel hits the obstacle.
- check the pressure regularly, when the tyres are cold;
- slow down before potholes, drain covers and speed bumps;
- avoid mounting kerbs and park without touching the kerb;
- after a hard impact, check the sidewalls and wheels;
- do not ignore new vibrations or the car pulling to one side.
Are low-profile tyres often run-flats?
On some cars, low-profile tyres are also run-flats, meaning they are designed to keep going for a limited distance after a puncture. It is not a general rule: it depends on the vehicle and the choice of tyre.
To find out whether you have them and what to do if you get a puncture, read run-flat tyres: how they work. Cars with low-profile and run-flat tyres often have no spare wheel: see no spare wheel.
Can you fit larger wheels than the original ones?
You can only fit the wheel and tyre sizes approved for your vehicle and listed in the registration document. Different sizes can cause problems at the roadworthiness test and for safety.
If you are considering a change of size, check the permitted sizes first and ask a professional. What is checked at the test is explained in tyres and the roadworthiness test.
Puncture on large wheels in Milan?
If you get a puncture on low-profile or run-flat tyres, SOS Tyre comes out 24/7 across Milan and its province, in 30 minutes on average, including for SUVs and sports cars, to wherever the vehicle is. Call +39 377 326 0999 or use the request for assistance, giving the full tyre size.
Frequently asked questions
Can a low-profile tyre be repaired after a puncture?
Yes, if the damage is a small hole in the tread and the tyre has not been driven on flat for long, the same criteria apply as for other tyres. Damage to the sidewall or shoulder, bulges and long cuts require replacement. The final assessment is the technician's.
Do large wheels make the ride less comfortable?
Generally yes: with a shorter sidewall the tyre filters out less of the road's unevenness, so the car transmits more vibration and noise. In return it gives more direct steering response. It is a trade-off between comfort, looks and driving precision.
How can you tell if a tyre is low-profile?
Look at the second figure of the size on the sidewall: it shows the ratio between sidewall height and width as a percentage. Low values, such as 40 or 35, indicate a sidewall that is very short relative to the width. You can also see it by eye: the wheel takes up almost the whole of the tyre.
Do low-profile tyres need a higher pressure?
The correct pressure is the one given by the vehicle manufacturer for that size, shown in the owner's manual and often on the label on the door pillar or inside the fuel filler flap. Do not increase it by guesswork: stick to the values given for load and speed.