Have you ever felt a vibration or steering “shimmy” during the first couple of kilometers after you first drive your vehicle since it’s been parked for a few days? Then, after driving for a few kilometers, the sensation goes away and the ride returns to normal – than you have experienced what’s known as flatspotting, where flatspots in the tyres tread develop when a vehicle is parked.
Whilst flatspotting is usually temporary (because the flattened area of the tyre rounds itself out), it can be permanent in some cases.
Why does flatspotting occur?
Whilst driving down a road at an average speed of 60km/h, as your tyres roll they transform to and from an unloaded state to a loaded state roughly 500 times during a single kilometer (that’s around 8 times per second!).
This constant cycle of load/unload results in what’s known as tyre deflection, whereby friction within the body of the tyre causes it to heat up and expand. Afterwards, When you’re vehicle is stationary (or parked), the heat in the tyre gradually cools down. As this cooling occurs, the area of the tyre making contact with the surface beneath the vehicle begins to flatting out as the weight of the vechile presses the tyre into the ground, adopting the shape of the surface. It is this shape or “flat spot” that causes the vibration and shimmy the next time you drive.
After you drive for a few kilometers the tyre begins to warm up again, and the flat area of the tyre will regain it’s original shape.
The severity of flattspotting can be increased by a number of factors, mainly:
- Period that the vehicle remains stationary
- Low tyre pressures
- Low ambient temperatures
- Heavy loads
Low Aspect Ratio Tyres
Due to shorter sidewalls and because the bulk of their load capacity gets absorbed by the deflection of their wider tread, low aspect ratio tyres have a reduced amount of flex, which means they are more susceptible to flatspotting.
How to minimise flatspotting
Whilst there is no clear way to absolutely prevent flat spots from occurring, the ability to predict what will happen to a tyre under certain conditions helps to reduce the inconvenience caused by flatspotting.
During winter months, or when you have not driven your vehicle for a few days, flatspotting may be noticeable, although typically these flatspots your sort themselves out during the first few kilometers. During the day time, the warmer temperatures should prevent noticeable flat spots from occurring.
Parking or storing vehicles for long periods
This is when flatting will occur the most. Before putting your vehicle in storage you should make take the time to make sure the tyres are fully warmed up and then but the car up on blocks when you reach the storage destination. This will help you to avoid permanently flatspotting your tyres.
Getting your car serviced
Whenever you are taking your vehicle in for a service to do with your tyres (rebalancing, tyre rotation etc), you should ensure that you drive around for 5-10 kilometers beforehand to ensure flatspots do not prevent your mechanic from identify the source of any problems.