Spare tyre vs space saver vs sealant kit: which is better?

A full-size spare copes with any damage, a space saver gets you to a fitter, and a sealant kit only seals a small hole in the tread. The table below compares them side by side.

The trade-off runs the other way for weight and boot space, which is why many newer cars leave the factory with a space saver or a sealant kit instead of a full spare. This guide covers what each copes with, the limits once you have used it, what to check on it now, and what happens to the damaged tyre afterwards. If you have a flat right now and nothing usable in the boot, skip to getting a fitter to come to you.

Spare tyre vs space saver vs sealant kit at a glance

Full-size spare: the most capable, and the heaviest

A full-size spare is a normal wheel and tyre, so once it is on, the car drives as it did before. It copes with anything that has happened to the original tyre, from a nail to a blowout.

The costs are weight and space. A full-size spare weighs approximately 20 kg, according to TyreSafe, and it takes up the whole wheel well. It is also easy to forget. A spare that has sat untouched for years may be underinflated or perished, so check its pressure when you check the others and look at the date code on its sidewall.

One catch: on some cars the spare is a steel wheel, or a different size or type from the tyres on the car. Tyres of different sizes on the same axle are a major defect in the MOT inspection manual, so check the handbook for any limits, and treat a mismatched spare as a wheel to get you to a fitter rather than a permanent fix.

Space saver: copes with any damage, but keep to 50 mph

A space saver gets you past the same damage as a full spare, because it replaces the whole wheel. The law calls it a "temporary use spare tyre". That means a tyre designed for use only when a normal tyre has failed, and at a lower speed than normal tyres (regulation 3). It is narrower and often smaller than the wheel it replaces. TyreSafe notes reduced grip and different handling. The tread is shallower and the rubber softer, so it wears out quickly.

What is the speed limit on a space saver?

Keep to 50 mph or less. Above 50 mph the regulations' allowance for a temporary spare stops applying, so you risk breaking the law. TyreSafe adds that 50 mph assumes dry conditions. It also advises avoiding dual carriageways and motorways on a space saver where at all possible.

Some space savers carry a maximum speed label on the rim. Check it and your handbook, and keep to whichever figure is lower.

The law: Road Vehicles (Construction and Use) Regulations 1986, regulation 26(5) and regulation 27(3). Both allowances are written for a passenger vehicle that is not a bus. Regulation 3 defines that as a vehicle built solely to carry passengers and their effects. If you drive a van, follow the handbook and treat a temporary spare as a wheel to get you to a fitter.

Are space saver tyres safe?

Yes, for the job they are designed for: getting a car with a failed tyre to a fitter, at no more than 50 mph, at the right pressure. They are not safe to use as a normal tyre. Grip is lower, the car can feel different under braking and in corners, and the tyre is not built to last. There is no legal distance limit, but TyreSafe recommends using a space saver for no more than 50 miles; for the detail on distances, see how far can you drive on a spare.

What pressure does a space saver need?

Space savers run at a much higher pressure than normal tyres. TyreSafe gives 60 psi, and the British Tyre Manufacturers' Association (2014 position statement) notes that temporary spares are designed for higher pressures than standard tyres. Your handbook has the figure for your car, and a space saver that has sat in the boot for years can be well under it.

Which wheel does the space saver go on?

On a front-wheel-drive car, TyreSafe advises putting the space saver on the back and moving the rear wheel from that side to the front. On a rear-wheel-drive car it suggests the front, with a warning that this could damage a limited slip differential. Your handbook comes first. Four-wheel-drive and all-wheel-drive cars need more care, covered in our guide to space savers on 4x4 and AWD cars.

Does a space saver have to be the same size?

Not the same width, but it must be the right one for your car. Space savers are not universal. The RAC says the overall radius should be within 3% of the original. It also has to clear your brakes; your handbook or dealer can confirm.

Sealant kit: light and quick, but only for small holes

A sealant and inflator kit is what many newer cars carry instead of any spare. You connect the bottle to the valve, the compressor pushes sealant into the tyre and inflates it, and the sealant plugs the hole from the inside as the wheel turns. There is no jacking and no wheel to lift, which helps on a dark roadside or when the wheel nuts are too tight to shift. Our tyre repair kit guide walks through using one step by step.

The limits are real. TyreSafe lists four situations where a kit will not work:

• damage to the wheel rim;
• a tyre that has been deflated for a period of time;
• a puncture larger than 4 mm across;
• a hole outside the main tread area, on the sidewall.

A split, a blowout or a tyre off the rim are beyond it as well.

Once the tyre is sealed, TyreSafe advises driving a short distance slowly, then pulling over after a few minutes to recheck it. Stop for good if the pressure warning stays on or the tyre is visibly going down. Michelin says a sealed tyre should not be driven long distances, or above 80 km/h (about 50 mph), until a professional has checked it. It also suggests checking the expiry date on the bottle.

What happens to the tyre after sealant?

Sealant gets you moving; it is not a repair. The British Tyre Manufacturers' Association lists liquid sealants among the methods it does not recognise as repairs. It says a proper repair starts with taking the tyre off the wheel and inspecting it inside and out (BTMA, 2014 position statement). Whether the tyre can then be repaired depends on the damage and on the fitter. Some fitters will not repair a tyre once sealant has been used.

Where a repair is possible, the usual rules apply. The hole has to be in the central three-quarters of the tread and smaller than 6 mm across (Continental). Our guide can a puncture be repaired? sets those rules out in full.

Either way, tell the fitter you have used a kit before they start. Mention it too if the car has tyre pressure sensors, so the sensor can be checked while the tyre is off; if one needs changing, a TPMS sensor can be replaced at the car.

Flat tyre now: what each option lets you do

Whatever is in the boot, the first question is the same: is the car somewhere you can safely work on it? The Highway Code says to stop as soon as it is safe, and only to change a tyre if you can do so without putting yourself or others at risk (Highway Code, Annex 6).

Which is better for your car?

A full-size spare is worth carrying if your car has room for one and you often drive long distances, rural roads or late at night, when help is further away. For mostly town driving, a space saver is usually enough; a kit suits small cars where boot space matters most.

Two examples show the difference. A nail in the tread on a town run is the job a kit is made for, as long as the hole is small and you stopped before the tyre went flat. A kerbed and split sidewall on a fast A road at night is beyond any kit. Once the car is stopped somewhere safe, you need a full-size spare, a space saver or a fitter to come to you.

As a rule of thumb from fitting work rather than a published rule:

• Long motorway trips, rural roads or towing: a full-size spare, because it handles any damage and lets you carry on at normal speed.
• Mostly town and suburban driving: a space saver is a sensible middle ground. It covers any damage, and a fitter is never far away.
• Small cars where boot space matters most: a sealant kit, accepting that a sidewall cut or a blowout still means calling for help.
• Run-flat tyres: no spare at all is the design. The run-flat guide under related guides below explains how far they will go and whether they can be repaired.

Adding a space saver to a car that only has a kit

Many cars supplied with only a kit can take a space saver in the wheel well; your dealer can tell you whether yours can. Before you rely on one, check that:

• it is listed for your exact model, with an overall radius within 3% of your normal wheels;
• it clears your brakes, which your handbook or dealer can confirm;
• you also have a jack, a wheel brace and, if your car has locking wheel nuts, the key.

Check it before you need it

Whichever you have, five minutes with it now saves finding a problem at the roadside.

• Full-size spare: pressure to the handbook figure, the date code, the tread, and the sidewalls for cracking.
• Space saver: pressure (TyreSafe gives 60 psi; your handbook has the figure for your car), any speed label on the rim, and cracks in the rubber.
• Sealant kit: the expiry date on the bottle, that the hose and plug are there, and that the compressor runs from your 12V socket.
• Tools: the jack, the wheel brace and the locking wheel nut key, all where you can find them. If the key has gone, a fitter can remove locking wheel nuts at the car.

Do you legally need a spare tyre, and will it pass an MOT?

No. We found no UK requirement to carry a spare, and the MOT does not test one: the MOT inspection manual tells testers to inspect only the wheels and tyres fitted to the car, and to tell you about any defect they notice on a spare. A car presented with a space saver fitted is different. TyreSafe says it will not pass, and the same manual lists tyres of different sizes on one axle as a major defect.

Why do new cars not have a spare wheel?

Mostly weight, cost and efficiency. TyreSafe notes that many modern cars are no longer supplied with a space saver, as manufacturers try to cut weight and manufacturing costs and improve efficiency (TyreSafe). Cars without a spare usually carry a sealant kit or run on run-flat tyres; lift the boot floor to see.

Getting a fitter to come to you

Whichever one is in your boot, it is a temporary fix. A space saver should come off as soon as you can manage, ideally the same day, and a sealed tyre needs to come off the wheel and be inspected. We come to the car, at home, at work or wherever it is safely parked, typically 30 to 60 minutes after the call, 24 hours a day. We repair the tyre to BS AU 159 where the damage allows, or fit a new one in 20 to 30 minutes, and you can put the space saver away.

What the fitter checks: the damaged tyre comes off the wheel so the inside can be inspected for damage from being driven flat. If sealant has been used, the fitter will tell you on the spot whether the tyre can still be repaired or needs replacing; some fitters will not repair a sealed tyre. Then the wheel goes back on and the pressures are set.

When you call, it helps to have:

• where the car is, and whether it is parked off the road;
• the tyre size from the sidewall of the damaged tyre or the one on the other side of the same axle, not from the space saver;
• which of the three you used, and whether sealant has gone into the tyre;
• whether you have the locking wheel nut key.

For a flat that cannot wait, our 24/7 emergency tyre call-out costs the same at night, weekends and bank holidays. To get off a space saver or a sealed tyre the same day, book a tyre fitted at home or work. Call 07717 389637.

Sources

Checked on 2 October 2026. Which option suits which driver, and what a fitter checks, are trade judgement from fitting work rather than a published source, and are written that way.

• legislation.gov.uk, Road Vehicles (Construction and Use) Regulations 1986, regulations 3, 26 and 27
• GOV.UK, MOT inspection manual, section 5: axles, wheels, tyres and suspension
• GOV.UK, The Highway Code, Annex 6 and rules 274 to 287
• TyreSafe, What is a space saver wheel or tyre and Temporary repairs: how do tyre repair kits work?
• British Tyre Manufacturers' Association, Minor repairs to passenger car and light van tyres (position statement issued 2010, reviewed 2014; PDF)
• Michelin UK, Everything you need to know about tyre sealant for cars
• Continental Tyres UK, Tyre repair
• RAC, Space saver wheel guide: know before you buy

Photo: Francesco Ungaro on Pexels

Frequently asked questions