A flat spot is a slightly flattened section of a tyre where it has rested under the car's weight, and it causes a vibration when you first drive off. After a car has stood for a while, this is common and usually temporary, easing as the tyres warm and regain their round shape. Permanent flat spots from long storage or a deflated tyre, though, need replacement.
What causes flat spots
When a car sits in one position, the weight presses the tyres against the ground at a single point. Over days or weeks, especially in cold weather or with low pressure, the tyre can take a temporary set there. The result is a thump or vibration as you pull away, fading as the tyres flex back into shape on the move. The longer and colder the stand, the more pronounced it is.
Temporary vs permanent
Most flat spots are temporary: a few minutes of driving warms the tyres to their operating temperature and the vibration disappears. Continental notes that more severe, semi-permanent flat-spotting sets in once tyres stand under load for around a month or longer, especially in high temperatures or at low pressure, and that normal driving won't remedy it (source). Permanent flat spots also form when tyres are badly under-inflated, or when a tyre has been driven on while flat. If the vibration doesn't clear after a good drive, the damage is likely permanent.
How to prevent them
Prevention is simple. Keep tyres at the correct pressure (or slightly higher for long storage), and move the car occasionally so it doesn't rest on the same spot for months. For seasonal or stored vehicles, the same care that protects against ageing applies, and it's worth a pre-trip check, especially on a caravan or trailer that stands a lot.
Flat spots from hard braking
There's a second kind of flat spot: one worn into the tread by an emergency stop that locks a wheel, scrubbing rubber off in one place. Modern ABS makes this rare, but it can happen. Unlike a standing flat spot, this one is physical wear and won't recover, so the tyre usually needs replacing if it causes vibration.
Flat spot or something else?
A flat-spot vibration is worst on the first mile of a cold morning and fades as you drive; other vibrations do not. That pattern is the quickest way to tell them apart.
| How it behaves | Likely cause | What to do |
|---|---|---|
| Thump or shudder when cold, gone after a few miles | Temporary flat spot | Nothing; drive it out |
| Vibration at one speed band, warm or cold | Wheel imbalance | Rebalance, see wheel balancing |
| Constant, worse with speed, never fades | Permanent flat spot, buckled wheel or damaged tyre | Inspection; likely replacement |
| Only when braking | Brake discs | Brakes checked |
| Pulling to one side as well | Alignment or a soft tyre | Pressures, then alignment |
If you are not sure, drive for twenty minutes on a mixed route and pay attention. A flat spot that has gone by the end of the drive is temporary. A shake that is still there is something else, and our guide to steering wheel vibration walks through the other causes.
Which tyres and vehicles flat-spot most
Heavy vehicles, low-profile performance tyres and anything left standing through a cold winter are the usual candidates.
- Caravans, trailers and motorhomes stand for months at a time under a constant load, often on the same patch of drive or grass.
- Performance and low-profile tyres have stiffer construction and less sidewall to flex, so a set can hold its flattened shape for longer. Some high-performance tyres are known for it, and their drivers accept a rough first mile.
- Cars laid up over winter, classics or second cars, where cold rubber stiffens and holds the set.
- Under-inflated tyres on any car. The lower the pressure, the bigger and deeper the contact patch, and the more set the tyre takes.
- Pool cars and vans that sit fully loaded over a bank holiday weekend.
Age makes it worse. Rubber loses some of its elasticity over the years, so an older tyre recovers more slowly from a stand than a fresh one, which is one more reason to check the date code on a vehicle that stands a lot.
Storing a car for weeks or months
The aim is to reduce the load on the tyre, keep the pressure up and move the contact patch now and then. Do as many of these as the situation allows:
- Inflate before the lay-up. Set the tyres towards the top of the handbook range, or a little above the normal figure, and reset them before the first proper drive.
- Move the car every few weeks, even by half a wheel turn, so a different part of the tyre carries the weight.
- Park on a hard, dry surface. Gravel or grass hold damp against the rubber and press unevenly into the tread.
- Take weight out of the vehicle where you can: empty the boot, drain a caravan's water tanks.
- Use tyre cradles or, for long storage, axle stands so the tyres carry little or no load. Cradles spread the contact patch; stands remove it entirely.
- Keep the tyres out of the sun with covers, which also slows ageing and cracking.
None of this needs special skill, and it is the same routine that protects a stored winter or summer set, see the seasonal tyre storage guide. The one thing not to do is leave a car standing on a flat tyre for weeks: the sidewall creases under the rim and the tyre is usually finished.
Before you drive a car that has been standing
Check pressures, tread and sidewalls before the first drive, because a stood car can go from legal to illegal without moving an inch.
- Pressures. Tyres lose air slowly whether they are used or not. Set all four, and the spare, to the placard figure.
- Tread. The legal minimum is 1.6mm across the central three-quarters of the tread, around the full circumference, as set out on GOV.UK. Driving below it risks a fine of up to £2,500 and 3 penalty points per tyre.
- Sidewalls. Look for cracking in the rubber, especially on older tyres and those that have stood in sunlight. Cracked or perished tyres should not be driven on, see cracked and perished tyres.
- Flat spots. Drive gently for the first few miles and let the tyres warm up before judging any vibration.
- Brakes. Light surface rust on the discs is normal and clears with a few gentle stops; a brake that has seized on a stood car is not, and it can feel like a tyre fault.
TyreSafe recommends checking pressure, tread and condition at least monthly, and a vehicle coming out of storage is exactly the case that routine is designed for.
When to replace
If a flat spot won't drive out, or the tyre is visibly worn in one spot, replace it. We can inspect and replace flat-spotted tyres at your home or work, from our base at Brent Cross, London NW2.
