What are Run-Flat Tyres?
The problem: You get a flat tyre and your car is instantly rendered undrivable.
Solution: A tyre that allows you to drive home or to a tyre centre without needing to be changed instantly.
This is what run-flat tyres aim to achieve.
What are run-flat tyres?
They are reinforced tyres that will hold the weight of a car even if there is no air inside. The walls of the tyre (the sides that don’t touch the road) are extra strong and allow the vehicle to be driven for a limited time at a limited speed.
It’s possible to get a puncture and not realise so most modern cars display a warning in the gauge cluster in the event of a tyre losing air.
Essentially, they are designed to allow drivers to ‘limp home’ without having to change a tyre on the side of the road.
Like many innovations, they come from a military requirement.
Bulletproof tyres naturally give a huge advantage to soldiers. For example, if a military vehicle had its tyres shot at, it could still flee or move to return fire without becoming a sitting duck.
The technology filtered down to the consumer vehicle market after improvements were made, making them cheaper and easier to manufacture.
No, consumer run-flat tyres are not bulletproof – only puncture-proof.
Different kinds of run-flat tyres:
These tyres have an additional ring of material around the wheel (inside the tyre). They can support a vehicle’s weight when punctured.
These are the most common kinds of run-flat tyres. They have extra strong, reinforced tyre walls and rubber which support the weight of a vehicle temporarily when a puncture occurs.
In this system, the tyres are filled with an extra lining that fills and blocks a hole in the event of a puncture. Depending on the puncture’s severity, they can permanently seal the hole or allow it to only lose air very slowly.
They should just have solid, rubber-filled tyres
For automotive applications, this won’t work. Other than the huge increase in cost due to the extra rubber needed, is the weight.
If you’ve ever picked up a car tyre, you’ll know they aren’t exactly light. Having 4 solid rubber tyres on a vehicle would add considerable weight, changing the handling of the car and adding more stress to the brakes.
Most passenger vehicles use around 1% more fuel for every additional 25kg of weight they carry so ‘low fuel consumption’ wouldn’t be much of a brag for manufacturers.
Furthermore, at high speeds, a fast-spinning heavy solid-rubber wheel can rip apart.
The air’s main role is to cushion vibrations from imperfections on roads so solid tyres would result in an uncomfortable, harsh ride.
Pros of run-flat tyres:
Other than allowing drivers to avoid having to change a flat tyre on the side of a highway, saving space is also a big plus.
Manufacturers can remove a spare tyre and the breakdown tools and jack needed to replace them which often benefits the cargo area.
No more driving around with a bright orange space-saver tyre either.
Are they any cons?
Run flats are not available for every tyre choice. If you drive a common vehicle with standard wheels, you’ll likely have the option. However, drivers who own rarer vehicles or upgrade their wheels may not be so lucky.
If you get a puncture in a remote area, for example, a regional tyre centre may not stock your run-flats which mean they’ll have to be ordered in.
With the added material and technology, run-flat tyres cost more. Depending on the brand and sizing, expect to pay 50% more in some cases. Run-flats might be better time-savers than money-savers.
Furthermore, most fun-flats don’t have the life expectancy of regular tyres so you’ll likely have to replace them sooner. Keeping all tyres in good condition by rotating them will maximise the lifespan.
Most run-flats result in a harsher ride. With the sidewalls and rubber much harder to support the vehicle in the event of a puncture, ride comfort is sacrificed.
Manufacturers are on top of this, however. Most newer cars that come standard with run-flats have specially tuned suspension to counter the increased vibrations.
They are a great idea for some people and a bad idea for others. If you drive a common vehicle with standard wheels in populated areas, run-flats are likely a good choice.
On the other hand, the added cost and (possibly) shorter lifespan and with the difficulty in replacing run-flats in remote areas might sway drivers to stick with traditional tyres.
Contact your local tyre centre and get some specialist advice.
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