A flat tyre: the decision, and spare, space saver, sealant or run-flat

A flat tyre is the one breakdown most drivers expect to sort out themselves, and the part that goes wrong is usually not the wheel. It is the decision made in the first minute: where to stop, whether to get the jack out at all, and whether what is in the boot can take the car where it needs to go. The Highway Code, which covers England, Scotland and Wales, puts the whole of it in two sentences in its Annex 6: "If you have a flat tyre, stop as soon as it is safe to do so. Only change the tyre if you can do so without putting yourself or others at risk - otherwise call a breakdown service."¹ What "safe" and "at risk" mean at the roadside, and what each kind of spare will and won't do for you, is the rest of the page.

The callout's jack clause is lesson 19's subject, "Changing a wheel safely", which follows this one. This lesson decides whether you get that far. Two sections below state law: the space saver's, for Great Britain and Virginia, and the run-flat's, for Great Britain. This is general information, not legal advice. The rules differ between England and Wales, Scotland, Northern Ireland and each US state, and they change.

UK words come with the US word the first time: tyre (tire), space saver (compact spare), boot (trunk), bonnet (hood), hard shoulder (shoulder). Speeds are in mph with km/h, as the handbooks give them.

If a tyre bursts while you're driving

A slow puncture gives you time. A burst does not, and the one thing that matters then is what your hands and feet do in the next few seconds.

NHTSA's page on tyres gives one goal: "The goal in any blowout is to keep the vehicle balanced and controllable."³ Beyond that goal NHTSA gives no physics, and this course adds none. The two countries' advice is short, and it agrees on the point that matters:

They agree on the part that matters: a firm grip on the wheel (NHTSA says with both hands), nothing sudden with the brake or the accelerator, and slowing down only as the car allows. This course reads the two together that way. NHTSA adds that the steps are the same whichever tyre goes; you just feel a front burst "more in the vehicle's steering" and a rear one "more in the seat or body of the vehicle".³ Honda's handbook for the 2024 Civic sold in the US covers a tyre that goes flat while you drive: "grasp the steering wheel firmly, and brake gradually to reduce speed. Then, stop in a safe place."⁵ Honda's is for a tyre going flat, not a sudden burst, and it has you brake gently; NHTSA, for a blowout, holds speed first and slows once the car is stable. Neither has you do anything sudden. What to do with a car that pulls or wanders is driving, which this course does not teach; what to do once it's stopped is the rest of this lesson.

Where to stop: as soon as it is safe, and no sooner

Three sources pull slightly different ways here, but they aren't really in conflict.

Toyota, in the handbook for the 2023 Corolla sold in the US, says: "Do not continue driving with a flat tire. Driving even a short distance with a flat tire can damage the tire and the wheel beyond repair, which could result in an accident."⁴ The RAC, a UK motoring organisation that sells breakdown cover and repairs, weighs it the other way: "It's better to drive further and risk damaging the wheel rim than stop somewhere dangerous", naming a busy road with no hard shoulder as the example, "but only drive to the nearest safe point."⁸ Mazda, in its European English handbook for the Mazda3: "If you have a flat tyre, drive slowly to a level spot that is well off the road and out of the way of traffic to change the tyre. Stopping in traffic or on the shoulder of a busy road is dangerous."⁶

On this course's reading, they're describing one decision from two sides. Toyota is telling you what driving on a flat costs (the tyre and the wheel, and possibly an accident); the RAC, which sells breakdown cover, and Mazda are telling you what stopping in the wrong place costs. Annex 6's "stop as soon as it is safe to do so" joins them: the shortest drive, slowly, to the nearest place off the road and out of the traffic. Lesson 16, "When the car stops: where, who stands where, and the call", named those places: the Highway Code's "place of relative safety", with somewhere designed for parking the safest.²

The decision: change it yourself, or call

In Great Britain, Annex 6's test is whether you can change the tyre "without putting yourself or others at risk".¹ This is advice, with no MUST in it, and it leaves "risk" to you. The handbooks and the motoring organisations fill it in.

Night on the M62

Before the table, try one. It is night on the M62 over the Pennines, and a rear tyre goes flat. The driver moves left and stops in an emergency area. The boot holds a space saver and a jack, the flat is on the nearside (the left, in Great Britain), away from the traffic, and she thinks she could have it done in fifteen minutes.

The conditions

Changing a wheel is Yours, on conditions, and these are the conditions:

If any condition fails, it's Call someone. Two readings are this course's own. The last row depends on the scene: a flat on the traffic side with the traffic close is a call. And a lay-by on a fast road counts as the fast road, so the callout's steps apply there and the wheel is a call. In the US, the rows that come from the handbooks apply as they stand; the motorway and Rule 276 rows are Great Britain's, and the US freeway paragraph below takes their place.

Nissan's two lines come from the handbook for the 2024 LEAF sold in the US, and they are written about its sealant kit, because that car carries no spare. On this course's reading they apply at least as strongly to a wheel change, which keeps you at the wheel for longer.

No source read says not to change a wheel in the dark, and the RAC, which sells breakdown cover and repairs, lists a torch "for working at night" in its kit.⁸ Rule 276's advice is not to stand, at night, where you block other drivers' view of your lights,² and on this course's reading, kneeling at a rear wheel can do just that. Darkness raises every risk in the table (you're harder to see, and so is the ground), and this course's reading is that it tips a close decision towards a call.

For a US freeway, no official source read tells a driver whether to change a wheel on the shoulder herself. The California Driver Handbook's freeway steps are to stay in the car, belted, unless one of three things holds: not enough space on the shoulder, a guardrail, or an area to stay safely away from the freeway lanes;¹⁶ they don't include a wheel change. This course's reading is the same as for a motorway: on a freeway shoulder, it is a call, and the callout's US steps are the ones to follow.

Most of the time, calling means a breakdown service you pay for or already have cover with. In the UK the AA, the RAC and Green Flag sell cover and repairs, and in the US AAA clubs sell roadside assistance and run a repair network; this course recommends none of them. Free help is narrower. In parts of California, the Highway Patrol's Freeway Service Patrol, at commute times, will "Change a flat tire."¹⁶ In England, National Highways can send "other help as required, such as a Traffic Officer", once the emergency services alert it,¹⁰ but no source read says traffic officers change wheels.

What your car carries

Before any of this, you need to know what's in your boot, because cars differ more than people expect. Of the four handbooks read for this lesson, the 2023 Corolla sold in the US carries a compact spare; Honda's handbook for the 2024 Civic sold in the US covers a compact spare and a sealant kit, each marked "Not available on all models"; the Mazda3's European handbook covers both a temporary spare and a kit on "Some Models"; and Nissan's handbook for the 2024 LEAF sold in the US says plainly: "This vehicle does not have a spare tire."⁴⁵⁶⁷ Some cars have run-flat tyres instead of any of these, and Mazda's handbook warns that a car "may or may not be equipped with a spare tyre, jack, wheel brace, and tool bag".⁶

A full-size spare

This course read no handbook for a car with a full-size spare. Lesson 8, "Tyres II: tread, damage, age, and when to replace", gave NHTSA's warning that every spare ages because spares seldom get replaced, and that a full-size spare is for emergencies such as a flat, not a replacement for worn tyres.³ Lesson 7, "Tyres I: pressure, the placard and TPMS", had you check its pressure with the others and showed how to read the date code on its sidewall.

A space saver

A space saver is a narrow spare. Mazda calls its own "lighter and smaller than a conventional tyre", and "designed only for emergency use and should be used only for VERY short periods."⁶ Toyota's is marked "TEMPORARY USE ONLY" on its sidewall.⁴ Each handbook read that has one sets limits for its own car:

The speeds agree, and they're still three handbooks, not yours. Lesson 1, "What a car is made of, and why the handbook comes first", made the same point with a fourth, Nissan's for the 2023 LEAF sold in the UK, which covers a temporary spare with the same 80 km/h (50 mph). The 2024 LEAF sold in the US has no spare at all: same model, two markets, two answers. The other rows do not agree, and that's the lesson in them. Mazda forbids its temporary spare on the front of a Mazda3, because "Handling will be affected. You could lose control of the vehicle, especially on ice or snow bound roads". Honda forbids it on the front of a manual Civic, for a different reason: it "may damage the differential", part of the drive to the wheels. Toyota has no such rule, and for a front flat on snow or ice it says to put the compact spare on a rear wheel and move a full-size rear tyre to the front, so that the chains go on the front.⁴⁵⁶

Why the car's systems change. Toyota gives the reason for its own car: with the compact spare fitted, "The vehicle speed may not be correctly detected", and so a list of systems, starting with "ABS & Brake assist", VSC and TRAC (Toyota's stability and traction control), "may not operate correctly".⁴ That's Toyota's account for the Corolla, and it goes no further; the other handbooks read do not give one.

The pressure warning. Lesson 7 taught what the tyre pressure warning light does. That light may not watch the spare. Toyota: the compact spare has no warning valve and transmitter, so "low inflation pressure of the spare tire will not be indicated by the tire pressure warning system". Honda says its light comes on and a message appears when the spare is fitted, and "this is normal".⁴⁵ Mazda has an instruction about its own system once the spare is on, and your handbook will say whether yours has one.⁶ So on a space saver the gauge check is yours, and the light isn't telling you about that tyre.

The space saver and the law

This is general information, not legal advice.

In Great Britain, regulation 27 of the Road Vehicles (Construction and Use) Regulations 1986 lists the tyre defects that stop a car being used on a road, starting with a tyre that is "unsuitable having regard to the use to which the motor vehicle or trailer is being put or to the types of tyres fitted to its other wheels". Paragraph (3) deals with a temporary spare against that rule: "Paragraph (1)(a) does not prohibit the use on a road of a passenger vehicle (not being a bus) by reason only of the fact that a wheel of the vehicle is fitted with a temporary use spare tyre, unless the vehicle is driven at a speed exceeding 50 mph."¹¹ The regulations define a temporary use spare as one designed for use only "in the event of the failure of one of the tyres normally fitted to a wheel of the vehicle" and "at a speed lower than that for which such normally fitted tyres are designed".¹¹

So the law allows a space saver only up to 50 mph. That isn't a speed limit for the car; it is the point above which the exemption no longer applies, and the unsuitable-tyre rule can. The handbook sits beside it, and here the three handbooks read agree with it. Another car's handbook may be stricter, and if it is, the handbook is the one to follow. Fitting and driving on a space saver is Yours, on conditions: the handbook's speed and its other limits, and a tyre fitter as soon as you can get there. The regulations extend to Great Britain; Northern Ireland's rules weren't read by this course.

In the US, this course read no federal or state rule on how fast a car may go on a compact spare, so the limit there is the handbook's. One state rule does touch it. Virginia's safety inspection, run by the State Police, rejects a car if it "has installed on any axle a space saver emergency spare tire that is intended for temporary use".¹² So in Virginia a car on its space saver fails inspection. On this course's reading, that's one more reason to get the tyre fixed and the spare off. Lesson 22, "The US: state inspections, emissions tests and tread law", covers inspection itself.

A sealant kit

Many cars carry a kit instead of a spare: a bottle of sealant and a small compressor that plugs into the car. It's for one small hole in the tread, and the handbooks spell out when it will not work. Using one is Yours, on conditions, and these are the conditions, in each maker's words:

Sources: each maker's handbook for that car.⁵⁶⁷

Look at the size row. Two makers say about 4 mm and the third says about 6 mm, so "the kit handles small holes" is true and "the kit handles holes up to 6 mm" is Nissan's figure for the LEAF, not a rule. The puncture row differs too: Honda and Nissan count tyres, Mazda counts holes in the tyre. All three also say to leave the nail or screw in the tyre. Honda gives the reason: "If you remove it from the tire, you may not be able to repair the puncture using the kit."⁵

Four more cautions come from the handbooks:

• Where you run it. Honda's compressor runs with the engine on, and its warning is about carbon monoxide: "Only run the engine to power the air compressor with the vehicle outdoors." It adds that "an enclosed or even partly enclosed area" is enough to be dangerous.⁵ Honda also says to put the kit "on flat ground near the flat tire, and away from traffic."
• Where you stand. Nissan: "Do not stand directly beside the damaged tire while it is being inflated because of the risk of the rupture."⁷
• How far and how fast. Each kit has you drive about 10 minutes to spread the sealant, below 50 mph (80 km/h), then check the pressure. If it has fallen below about 19 psi (130 kPa), the repair has failed: Honda, "Do not add air or continue driving. The leak is too severe. Call for help and have your vehicle towed."⁵⁶⁷
• What it is not. Before its kit instructions, Nissan says of a flat LEAF: "If possible, have the vehicle towed to a facility that can repair or replace the flat tire." And: "The Genuine NISSAN Emergency Tire Sealant cannot permanently seal a punctured tire. Continuing operation of the vehicle without a permanent tire repair can lead to a crash." Mazda recommends "that the tyre be replaced with a new one as soon as possible".⁶⁷ Toyota and Nissan both warn that liquid sealant may stop the tyre pressure sensor in the wheel working properly, and both say to have it replaced.⁴⁷

A nail in an Ocala car park

A driver comes out of a supermarket in Ocala to find her 2024 Civic's rear tyre soft, with a nail head showing in the middle of the tread. The car park is open-air and the car is in a bay well away from the traffic lane. The boot has Honda's kit.

Step 1: can the kit be used? Go down Honda's list. The sealant's date is on the bottle: in date. One tyre. The nail is in the tread, in the part that touches the road, not the sidewall. The hole around a nail is small; she can't measure it, but a nail is exactly what Honda's "small puncture, from a nail for instance" means. She did not drive on it flat, and the tyre is still on the rim. Every condition is met.

Step 2: where she runs it. Outdoors, in the open, as Honda requires for the engine, with the kit on flat ground by the tyre. A multi-storey car park would change this answer: it's "partly enclosed", and she would call instead of running the engine there.

Step 3: leave the nail. Honda says not to remove it.

Step 4: drive, check, decide. About 10 minutes, under 50 mph, then check the pressure. Honda gives three answers. At 32 psi (220 kPa) or more, its figure for a rear tyre on this car, she drives on for up to another 10 minutes towards a tyre fitter, under 50, and checks again if she isn't there yet. Between 19 and 32 psi, she pumps it back up to 32 and does the same. Below 19 psi (130 kPa), the kit has failed and she calls for a tow. At the fitter, the tyre is repaired or replaced.

Run-flat tyres

This is general information, not legal advice.

A run-flat tyre is built to be driven on for a limited distance after it loses air; TyreSafe, a UK tyre safety charity backed by tyre makers, carmakers and retailers, says run-flats "have a reinforced sidewall".¹⁵ In Great Britain, on this course's reading, regulation 27(2) is where the law provides for them: paragraph (1) does not prohibit using a car with a tyre "which is deflated or not fully inflated" and has a cut, bulge or exposed cord, "if the tyre and the wheel to which it is fitted are so constructed as to make the tyre in that condition fit for the use to which the motor vehicle or trailer is being put" and the tyre's sides are marked to show it.¹¹

How far and how fast is the handbook's, and this course read no handbook for a car with run-flats. The general figure read here comes from TyreSafe, the industry-backed charity: "Run flat tyres are designed only to be used for 50 miles at a maximum speed of 50 mph."¹⁵ Your handbook's figure is the one for your car. TyreSafe adds a warning of its own: "It can be difficult to tell just by looking if your car's run-flat tyres are in a deflated condition."¹⁵ On this course's reading, that leaves the pressure warning and a gauge as the ways you would know.

TyreSafe, the industry-backed charity, is clear about one case: driving on a punctured or deflated run-flat "subjects the tyre structure to high stress", which it says makes the tyre "both unsuitable and unsafe to repair".¹⁵ Beyond that case the sources read don't give one answer, and this course doesn't settle it. TyreSafe goes on: "A fully qualified tyre repairer may struggle to detect under inflation in a run flat, which is why several associations do not recommend repairing a run-flat tyre."¹⁵ USTMA, the US tyre makers' trade body, says "some tire manufacturers may have repair limits or restrictions for some tires, such as runflat tires and others."¹⁴ Either way, it's a question for the tyre fitter and your tyre maker's policy, not for the roadside.

A proper repair, and why a plug from outside isn't one

Repairing a puncture is Call someone, because it's a tyre fitter's job, and this course doesn't teach plugging a tyre. What it can teach is what to ask for.

In the UK, the standard is the British Standard BS AU 159, which this course read as summarised by the BTMA, the British tyre makers' trade body, not in the original. Its extracts are from the 1997 issue (suffix f), and the BTMA says the standard is "currently suffix g", an issue this course did not read. The summary: "Some minor damage to car or light van tyres can be safely repaired; principally punctures to the central area of the tread that are less than 6mm in diameter." The repairer must "Remove the tyre from the wheel and thoroughly inspect, both internally and externally." Among methods "not recognised as acceptable" are "Liquid sealants.", "Plugs applied externally to fitted tyres." and "Temporary repairs." For a repair it accepts, it requires "Repair in area 'T' only" (a central band of the tread, set as a share of the tyre's width), by a "Rubber only combination plug patch." or a "Rubber only patch and penetration filling material.", and the procedure marks the patch's outline "on the inner liner": a patch on the inside either way. And a tyre repaired to the standard is "able to operate at their original speed and load capabilities."¹³ The BTMA adds that the standard "does not apply to T-type temporary use spare tyres" (space savers).

In the US, the page of USTMA, the US tyre makers' trade body, says to consider a repair "only if damage is limited to the tread area only and the puncture injury is no greater than 1/4 inch (6mm) in diameter", that the tyre comes off the wheel for inspection, that the hole is filled with a plug and the inside sealed with a patch, "(A plug alone is an unacceptable repair.)", and: "NEVER perform an outside-in tire repair or on-the-wheel repair."¹⁴ The two industries' rules agree in substance: tread only, 6 mm, off the wheel, inside sealed.

Why off the wheel. TyreSafe, the industry-backed charity, gives the reason: permanent repairs need the tyre off the wheel "to allow a thorough inspection internally as well as externally to ensure there is no hidden damage which could result in a catastrophic failure."¹⁵ And the BTMA's summary, the British trade body's, lists what that inspection can find that rules a repair out, including "Secondary effects, e.g. under-inflation/deflation damage".¹³ On this course's reading, that is the link back to Toyota's warning at the top: driving on a flat can do damage that doesn't show from outside, and that damage is what turns a repairable puncture into a new tyre.

TyreSafe, the industry-backed charity, says repairs "must only be carried out by a tyre specialist and in accordance with the current British Standard AU159", and separately that "To stay compliant with the law" repairs can only be made on the central three quarters of the tyre.¹⁵ This course read no statute that makes either a legal requirement, so it reports them as TyreSafe's.

What people get wrong

"A plug from outside is a repair." The two trade bodies, the BTMA in the UK and USTMA in the US, both reject it, above.

"A space saver is just another wheel." Toyota: with it fitted, the car's braking and stability systems "may not operate correctly"; every handbook read limits the speed; and in Great Britain the law excuses it only up to 50 mph.

"A run-flat goes as far as you need." TyreSafe, the industry-backed charity, gives a general figure of 50 miles at 50 mph, and your handbook's may differ. Neither is "as far as you need".

"Sealant fixes it." Nissan: it "cannot permanently seal a punctured tire". The BTMA, the British trade body, lists liquid sealants among methods not accepted as a repair.

"Stop at once, wherever you are." Annex 6 says as soon as it is safe, and the RAC, which sells breakdown cover and repairs, says to drive on only to "the nearest safe point". Stopping in a live lane or on a narrow verge to save a wheel rim gets the trade the wrong way round.

Practice

For your plan

Add a wheel page to your car file, next to lesson 16's breakdown page: what the car carries and where, its limits in the handbook's words, the sealant's expiry date, and the number to call. Lesson 19 adds the wheel change itself.

Connections

Lesson 7 taught the tyre pressure warning that this lesson found may not watch the spare, and lesson 8 the damage that no kit or repair can fix. Lesson 16 set out where a car should stop, and lesson 17 takes the motorway steps in full. Lesson 19, "Changing a wheel safely", is the next step when this lesson's decision comes out yes. Lesson 20, "The law on a car's condition: Great Britain and Northern Ireland", comes back to regulation 27 as a whole.

Go deeper

• Your own handbook, its sections on a flat tyre and on the spare or kit. Read here in full for four cars; yours is the one that counts.
• The Highway Code, "Annex 6. Vehicle maintenance, safety and security", free. Read here in full. Short, and the official line for Great Britain on bursts and flats.
• NHTSA, "Tires", free. Read here in full from an archive copy. Its blowout section says what to do with your hands and feet.
• BTMA, "Tyre Industry Professionals", free. Read here in full. The trade body's summary of BS AU 159; the standard itself is sold by BSI and wasn't read.

Sources

1. The Highway Code, "Annex 6. Vehicle maintenance, safety and security", updated 29 January 2022. Great Britain. Read: full text, re-read 26 September 2026 through the GOV.UK content API.
2. The Highway Code, "Breakdowns and incidents (275 to 287)", updated 14 September 2021. Great Britain. Read: full text, re-read 26 September 2026 through the GOV.UK content API.
3. NHTSA, "Tires". US. Read from Internet Archive capture 20260923145155, the newest readable one (nhtsa.gov refuses automated readers; the live page is linked). Read: full page, 26 September 2026.
4. Toyota, 2023 Corolla Owner's Manual (OM02568U), US market, section 7-2 "Steps to take in an emergency". A maker's handbook for its own car. Read: pp. 370 to 379, re-read 26 September 2026.
5. Honda, 2024 Civic Sedan Owner's Manual, "Changing a Flat Tire" and "Temporarily Repairing a Flat Tire", online, US market. A maker's handbook for its own car. Read: full section, re-read 26 September 2026.
6. Mazda, Mazda3 Owner's Manual, "Flat Tyre", online, European English edition (8GD7-EE-17H). A maker's handbook for its own car. Read: every page of the chapter, re-read 26 September 2026.
7. Nissan North America, 2024 LEAF Owner's Manual and Maintenance Information, US market. A maker's handbook for its own car. Read for this lesson: pp. 6-3 to 6-9 ("Flat tire", "Repairing flat tire"), 26 September 2026. Nissan UK's online LEAF handbook, which this course read earlier, returned an error on every page on 26 September 2026, so the US handbook is cited.
8. RAC (a UK motoring organisation that sells breakdown cover and repairs; not an official body), "How to change a tyre in 10 simple steps". No date shown. Read: full article, re-read 26 September 2026.
9. Green Flag (a UK breakdown provider that sells breakdown cover and repairs; not an official body), "Changing a tyre". No date shown. Read: full article, re-read 26 September 2026.
10. National Highways, "Driving on motorways", the government-owned company that runs England's motorways and major A roads. No date shown. Read: full text, re-read 26 September 2026.
11. The Road Vehicles (Construction and Use) Regulations 1986, regulation 27 and the definition of "temporary use spare tyre" in regulation 3, revised text on legislation.gov.uk. Extent England, Wales and Scotland. Read: regulation 27 in full and the regulation 3 definition, 26 September 2026.
12. Virginia Administrative Code, 19VAC30-70-130, "Tires; wheels; rims", the State Police's inspection rules. Virginia. Read: full section, 26 September 2026.
13. BTMA (British Tyre Manufacturers' Association, a trade body), "Tyre Industry Professionals", its summary of BS AU 159, reproducing extracts of the 1997 issue under BSI licence. No date shown. Read: full page, re-read 26 September 2026. The standard itself was not read.
14. USTMA (US Tire Manufacturers Association, a trade body), "Tire Repair Basics". No date shown. Read: full page, re-read 26 September 2026.
15. TyreSafe (a UK tyre safety charity backed by tyre makers, carmakers and retailers), "The Complete Guide To Punctures and Repairs". No date shown. Read: full page, re-read 26 September 2026.
16. California DMV, California Driver Handbook, "Section 8: Safe Driving (Continued)". California's official driver handbook. No date shown. Read: full section, re-read 26 September 2026.