One of the least-popular trends in modern car design is the almost total disappearance of the traditional full-size spare tyre / spare wheel. Most cars now come with a compact space-saver spare tyre or a canister of green goo and a compressor to re-inflate a punctured tyre. If you drive a BMW (or a Mini, which is owned by BMW), you probably don’t even get that, as most of their cars come with run-flat tyres instead, which are designed to be able to be driven with no air pressure for a short while.
Why have spare tyres / spare wheels disappeared?
There are several reasons why modern cars no longer come with a full-size spare wheel. The main reason is fairly simple – they are rarely ever used, and so there are considerable savings to be made by not fitting them.
The main three savings are cost, space and weight. A typical 17″ alloy wheel and tyre would cost the manufacturer about £100 per car, and weigh about 20kg. A full-size wheel is also bulky, so designers have to factor in providing enough space for the wheel to fit in or under the boot – which adds more bulk and weight to the vehicle. By replacing the full-size wheel with a space-saver spare wheel, the costs reduce and weight is saved. If you have a ‘breakdown kit’ of goo and compressor, the weight, space and cost savings are even greater. The saved weight makes a small difference to fuel economy and emissions, which can help lower a car’s CO2 rating (and possibly reduce road tax, etc.). The space issue is greatest in smaller cars like hatchbacks and sports cars, but the cost savings are universal.
With all of the above in mind, let’s look at the pros and cons of each tyre emergency alternative and assess the real-world implications.
Full-size spare wheel
The default spare wheel offering until the 1990s and now virtually non-existent, it was considered standard practice for all cars to come with five identical wheels and tyres – four on the road and one in the boot. This means that any tyre can be immediately replaced with the spare on the spot, and there are no limitations to speed and distance when the spare wheel is in place.
This factor is still an issue in more remote parts of the world, where it is easy to be a long way from your local Kwik-Fit. There is also the caveat that the spare is only useful if it is in good working order and not flat! This sounds obvious, but the number of people who never check their spare tyre, or use it to replace a flat tyre and never get the damaged unit fixed, is staggering. So it’s useless when you actually need it. Also, most drivers would never replace the spare tyre when replacing other tyres, so it would often be a different tyre to the other four anyway, which is less than ideal from a safety perspective.
Pros: convenient, but only if all four wheels are the same size; no speed or distance limitations when running spare wheel
Cons: expensive, heavy and bulky for something which is very rarely used; few people ever check the tyre pressure on the spare, meaning it is quite possible it will be flat when you need it.
Space-saver spare wheel
Compact space-saver spare wheels really emerged in the 1990s as manufacturers looked to start saving money and weight in their cars. It was also becoming more common for cars to come with different-sized front and rear tyres and/or directional tyres, meaning that it was possible that a car could have four different tyres for four wheels! This meant that one full-size spare wheel had a 75% chance of not being the right wheel for the job.
The problem with a space-saver spare wheel is that if you ever need to use it, the original wheel and flat tyre will not fit in the spare wheel well, so you have to carry it in the boot – which, of course, is no good if you already have a bootful of luggage. Space-saver spare tyres are also usually limited to a maximum speed of 50mph (80 km/h) and a maximum distance of about 50 miles, so it limits your options for getting to a suitable tyre shop.
Pros: cheaper, lighter and smaller than a full-size spare tyre; can be used for almost any tyre problem
Cons: your damaged full-size tyre won’t fit in the space-saver wheel well; limited speed and distance; vehicle handling and safety impaired
Breakdown kits (consisting of tyre sealant liquid and an air compressor) have become a lot more popular in recent years, and are now becoming the default solution for most new cars. However, they are far from perfect. The theory is that you squirt the green goo into the tyre valve and then use the compressor to reinflate the flat tyre. Again, this is a temporary fix and usually limited to about 50 miles at about 50mph. Whilst it does mean that you don’t have to worry about changing the tyre and emptying your boot, it is only really useful for relatively minor punctures and no good whatsoever for significant tyre damage.
Pros: re-inflating tyre means no need to change wheel on the roadside; maximum cost/space/weight savings (no spare wheel, wheel well, jack, tyre lever, etc.)
Cons: only suitable for minor tyre damage; limited speed and distance; using sealant usually makes tyre irrepairable.
Long championed by BMW, but generally disregarded by virtually every other car company, are run-flat tyres. These tyres feature a reinforced sidewall which allow you to continue driving on a punctured tyre even if it has lost all of its air (again, limited in speed and distance). The downsides to run-flat tyres is that they are again limited to minor punctures rather than serious cuts, and the reinforced sidewalls are much more rigid than those of a normal tyre, which usually seriously impairs their ride comfort compared to a regular tyre.
Pros: maximum convenience, as no need to stop to change or repair tyre; maximum cost/space/eight savings
Cons: only suitable for minor tyre damage; limited speed and damage; tyres are expensive; significantly reduced ride comfort.
Many people still bemoan the removal of full-size spare wheels from new cars, but the simple reality is that for the vast majority of people, it’s not a big deal. In fact, many people with go their whole driving lives without ever having a flat tyre or blowout. Certainly within Britain and most of Europe, breakdown assistance services are able to attend to your tyre emergency promptly, so your likelihood of being severely inconvenienced is slim. And a flat tyre is not the most common reason to call out your breakdown assistance – that’s a flat battery, and no-one carries a spare battery in their car.
Most new cars now come with breakdown kits instead of full-size or space-saver spares. It may not be a perfect solution for every situation, but covers most people’s needs most of the time.