BMW M340i's Tyre Bursts At 200+ Kph: Run-flats Save The Day [Video]
BMW cars are known for their impressive performance and dynamics. Its current portfolio in India has some models that are absolutely great to drive. People who buy these often drive fast... really fast. Have you thought of having a tyre burst at high speeds? Imagine losing a tyre when you are doing 200+ kph... Do you know what happens next? Well, you’ll lose control of the vehicle and crash out, unless you are on run-flat tyres. A video shared online shows how run-flats proved to be life-savers after a BMW cruising at 200+ kph had a tyre burst. Incidentally, BMW and Mini were the first carmakers to bring run-flats to India.
The clip opens by showing a BMW accelerating. The car here seems to be a BMW M340i. It is already doing 160+ kph at the start of the video. It keeps accelerating and soon crosses 200 kph. The driver keeps pushing. Soon, we see 205 kph on the speedometer. Suddenly, a loud bang is heard, which we then realise was from the burst tyre.
Losing a tyre doesn’t unsettle the car. The driver tries to decelerate, but remains in absolute control. The car doesn’t swerve violently, nor does it become numb to steering or braking inputs. It decelerates rapidly and soon comes to safe speeds. The video shows just how important run-flats are. If the car had regular rubber, losing control and crashing were definitely possible.
Run-flat tyres have reinforced sidewalls or additional supporting structures inside. A tyre burst will lead to a rapid loss in pressure. The reinforcement will, however, support the car’s weight and keep it under control and steerable. Its unique construction helps a run-flat tyre to drive for 100 odd kilometers at reduced speeds. This distance could vary slightly with the tyre and vehicle model.
Based on their structure and construction, there are two types of run-flat tyres- self-supporting and auxiliary supported. The former gets sidewalls reinforced with stiffer rubber compounds and stronger belts. Auxiliary-supported run-flats come with additional support structures- like a reinforced ring or band on the wheel rim- inside, which carries the load in the event of a puncture.
By now, you would have understood how important run-flats are in ensuring safety at high speeds. Additionally, these can save you a lot of time, as you don’t have to wait for tow trucks or do the tyre-change yourself. You can drive to the nearest tyre shop and get it replaced, minimising the downtime.
Run-flats are generally lighter than regular tyres, and can bring about improvements in fuel efficiency in the long run. if the vehicle is equipped with run-flats, the carmaker often refrains from providing a spare tyre, thereby saving weight and generating more usable boot space.
Now the cons. First, run-flats are significantly more expensive than regular tyres. If there is a tear or blowout in the run-flat, it is recommended by most manufacturers to get it replaced instead of opting for repairs.
Another problem is that these tyres deliver slightly harsher ride quality than regular ones, due to their stiffer sidewalls or the additional reinforcements inside. On some terrains, these can be more noisy and can also cause faster wear compared to normal tyres. Most run-flats come with tyre pressure monitoring systems (TPMS). Without these, it would be difficult to detect a puncture in these.
Finally, even today, run-flat tyres of certain sizes/ for select models aren’t readily available, especially in Tier 3 and Tier 4 cities, resulting in longer waiting periods.