A flat spot is a worn or deformed patch on one part of a tyre that is otherwise round, usually felt as a vibration at certain speeds. There are two quite different causes, one from braking, one from standing still, and they call for different responses.
Braking flat spots
The first kind is scrubbed in by a wheel that locks up:
- An emergency stop without ABS, or a fault that locks a wheel
- The tyre stops turning while the car still moves, grinding a patch flat
This kind is permanent. The rubber is gone, and if the flat spot is bad enough to cause vibration, the tyre usually needs replacing. Modern ABS makes it rarer, but a hard stop on a slippery surface or a seized brake can still do it.
Standing flat spots
The second kind comes from a car sitting still too long:
- The tyre rests on one spot under the car's weight and takes a set
- Worse in cold weather and over long periods
This kind is often temporary. After a drive, as the tyres warm and flex, the set frequently eases and the flat spot fades. Over very long storage, though, it can become permanent, at which point it behaves like the braking kind.
Telling them apart
The cause usually gives itself away:
- A flat spot that appears after a hard stop, and stays, braking, permanent
- A vibration after a car has been parked for weeks, that eases as you drive, standing, often temporary
A standing flat spot that does not warm out after a good drive has likely set permanently.
Preventing standing flat spots
For a car that will sit for a while, a few steps help:
- Move it occasionally, even a short distance
- Inflate the tyres a little higher for long storage
- Keep it off cold, hard floors where practical
- Avoid leaving it in one spot for months
The same care that protects stored tyres protects a parked car's tyres from taking a set.
From the workshop: two sorts of flat spot. One you've braked into, locked a wheel, scrubbed it flat, that's a new tyre. The other's from a car sat on the drive all winter; drive it, warm it through, and that one usually comes good. If the wobble won't go after a proper run, it's set for good.
Sources and accuracy. This reflects standard flat-spot diagnosis at the time of writing. Whether a flat spot has set permanently is best judged after driving. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What causes a flat spot on a tyre?+
Two things. A locked wheel or emergency stop can scrub a patch of tread flat, which is permanent. Or a car left parked for a long time can take a temporary set where the tyres rest, which often warms out after driving but can become permanent over long storage.
Do tyre flat spots go away?+
It depends on the cause. A flat spot from standing still usually eases once the tyres warm up on a drive. A flat spot scrubbed by a locked wheel during braking is permanent and does not recover, and may need the tyre replaced if it causes vibration.
Can flat spots cause vibration?+
Yes. A flat area on an otherwise round tyre makes the wheel turn unevenly, which you feel as a vibration, usually at certain speeds. A standing flat spot fades as it warms; a braking flat spot stays and may mean replacing the tyre.
How do I prevent flat spots when storing a car?+
Move the car occasionally, inflate the tyres a little higher for long storage, keep it off cold hard floors where possible, and avoid leaving it in one spot for months. These steps stop the tyres taking a lasting set while parked.