It’s not uncommon for some of us to leave our cars parked for long stretches spanning days, weeks – sometimes even months. If you’re one of these people, you may notice a slight ride disturbance or vibration the first time you drive the car, but it will usually disappear after a few miles of driving.
This phenomenon is known as flat-spotting, a condition that occurs when a tire has been stationary under vehicle load for a prolonged period. The tire has a flat spot in the area where it was in contact with the ground. Alarmed? Don’t be. Let’s dive into the causes of flat-spotting in a little more detail, plus tips on how to prevent it.
As you drive your car, each tire rapidly rotates on the wheel from a “relaxed state” to a “loaded state” approximately 480 times per kilometer (depending on your speed). This constant motion generates heat, which makes the rubber in the tires more supple – this is standard behavior for your tires.
Once you’ve stopped and parked your car, however, the contact patch of the tire can flatten slightly where it is in contact with the ground as the tires cool down. It’s especially likely to occur when the tires experience a dramatic swing in ambient temperatures, the car is parked overnight in cold temperatures, or the vehicle is in storage for a long time. Another factor is tire pressure, and whether the tires are underinflated or overloaded.
There are two types of flat-spotting: temporary and semi-permanent. The severity of a tire flat spot will depend on factors like size, load, internal structure, the ambient temperature, and the amount of time it is stationary.
In the majority of cases, flat-spotting is temporary. If a vehicle has been stationary for a few days or weeks – for example, if you’ve been away on vacation and parked the car at the airport – drivers may experience some slight vibrations during the first few miles of their journey. The flat spots will disappear once the tires have reached their operational temperature and regained their normal shape.
Semi-permanent flat-spotting will occur if the tires have been standing still under vehicle load for a month or longer. A typical situation where this can happen is if you’re storing your vehicle away for the winter months, or if it’s being transported overseas. The long standing times, especially in tandem with high temperatures and low tire pressure, can result in more severe flat-spotting that normal driving won’t remedy.
If you suspect that your tires have semi-permanent flat-spotting, you should contact your local tire specialist or garage in the first instance, and they’ll guide you through the options on how to fix it.
Maintaining the correct tire pressure is an effective strategy to mitigate the chances of flat-spotting happening.
Tires that are underinflated are more susceptible to a flat spot, and it’s generally advisable not to operate your tires when they’re underinflated or overloaded.
If you’re about to undertake a long-distance journey at high speeds with heavy loads, then you should increase the inflation pressure of your tires in line with the vehicle manufacturer’s recommendations.
Did you know that a slight increase of +0.2 bar in tire inflation pressure results in lower tire running temperatures? In turn, this decreases the likelihood of flat-spotting.
Similarly, if you’re about to park your car for a long time without driving, then slightly increasing the inflation pressure of the tires by +0.2 bar before parking will help to reduce the chances of flat-spotting.
In both instances, however, it’s important to remember that you should never exceed the maximum recommended cold inflation pressure for your tires.