I was driving southbound along the North-South Highway from Cameron Highlands to Kuala Lumpur when the tyre pressure monitoring system (TPMS) of our Mercedes-Benz C350e test car flashed its warning – the front left tyre was losing pressure.
I pulled over at the Ladang Bikam rest stop and found that there was indeed a puncture at the sidewall. Seeing that there was still some air left in the tyre, I opted to drive on in hopes of reaching the next rest stop with a petrol station to re-pressurize the tyre. In hindsight, that was bad decision making on my part.
After departing Ladang Bikam, the affected tyre held its pressure steady at 200 kPa for some time, with its front right counterpart at 250 kPa. The rear tyres, in accordance to spec, were inflated 30 kPa denser at 280 kPa.
After about 25-30km cruising at a lowly 70-80 km/h, the TPMS flashed its warning more vigourously as the front left tyre de-pressurized rapidly. Realizing it was a lost cause to proceed further, I pulled over again at Behrang rest stop and rang Mercedes-Benz's 24-hour customer support for help.
From the list of phone numbers printed on the Customer Care sticker, I managed to get hold of Cycle & Carriage Ipoh, who promptly sent a support car and flatbed tow truck to my rescue. Congested traffic on the highway meant that it was two hours before the CCB crew arrived at my location, but arrive they did, and with the car taken back to CCB Ipoh for a replacement tyre, I was promptly delivered back to the comforts of my home in Petaling Jaya.
The entire episode from my first phone call to CCB Ipoh to the point I stepped into the doorstep of my house lasted three and a half hours – a reasonable timeframe in hindsight, though three and a half hours can be a long time to pass if all you have to do is just sitting there and waiting. Thankfully, there was enough charge in the traction battery that I could sit in the car and idle with the air-conditioning switched on without burning a drop of petrol in the process.
No motoring writer likes sending a test car back on a flatbed, but this episode gave me the opportunity to ponder first-hand the pros and cons of the run-flat tyres which the C350e is equipped with; and because it needs to accommodate a large traction battery, the C350e’s boot has no room for a spare tyre, not even a space saver.
The immediate thought that crossed our minds in that long wait for the CCB crew was the inconvenience in not being able to change the flat tyre on our own and quickly get underway. That being said, if the car had been running on regular tyres, we would have been incapacitated on the spot without the ability to reach the rest area – not without significantly damaging those shiny 19-inch alloys at any rate.
When they first came into the market, run-flat tyres were derided for their brittle ride quality – an inevitable by-product of their super-stiff sidewalls. This is becoming a non-issue in recent times, however, as car makers have grown increasingly adept at counteracting the run-flat tyre’s inherent stiffness with careful suspension tuning.
There is also the cost factor to consider with run-flat tyres – they are significantly more expensive than regular tyres to purchase and they cannot be repaired. If you puncture a run-flat, you have to replace it. The super-stiff sidewalls are meant to support the vehicle's weight unaided by air only once - just like a motorcyclist's helmet.
Many of us, this writer included, take pride in our ability to change a flat tyre ourselves. I'd still say it's a good skill to cultivate, but it's perhaps best not having to do it alongside three lanes of speeding vehicles. Indeed, the actual sight of an errant motorist flying past traffic at obscene speeds along the emergency lane on our journey home served as a timely reminder of that.
Car makers and tyre companies now market run-flats as a safety feature, and on the evidence of my recent experience, that has become hard to disagree. They are not meant to be driven over extended distances without air, but the idea is that you should be able to go far enough to reach a safe location to stop. Inconvenient admittedly, but it's the safer option.