Flat tire and no spare? What to do

Why does your car have no spare?

Many newer cars leave the spare out to save weight and space. Instead, they carry a sealant and air pump kit, or run-flat tires.

Look under the trunk floor or in a side panel before you decide. Some cars hide a spare under the vehicle, and some keep a kit in a small bag.

• A sealant kit: a bottle of sealant and a small air pump.
• Run-flat tires: tires built to run a short way with no air.
• Nothing: no spare, no kit. Then you need a new tire or a tow.

Your owner's manual says which one your car has.

What should you do first?

Stop driving on the flat as soon as you safely can. Every block on a flat tire grinds the sidewall and can ruin a tire that was repairable.

1. Signal, slow down and pull off onto firm, level ground.
2. Turn on the hazards and set the parking brake.
3. Look at the tire: a nail, a cut, a bulge, or no sign at all.
4. Take a photo of the damage and of the tire's sidewall.
5. Check the trunk for a spare, a kit or tools.

A tire that went soft slowly, with a nail in the middle of the tread, has the best chance of a repair. A tire that went flat at speed and was driven on usually does not. USTMA says even a short drive while under inflated can damage a tire beyond repair.

What are your three options?

Seal and pump the tire with the kit, have a new tire brought to the car, or tow the car to a shop. Which one fits depends on the damage and where you are.

If you are on an interstate or a busy road and feel unsafe, call 911 before you try any of these.

Does the sealant kit fix the tire?

No. USTMA says a temporary tire mobility kit is not a repair; it only gets you to a tire service location so the tire can be checked and, if possible, repaired properly.

The kit can seal a small hole in the tread, like a nail or screw. It can't seal a cut in the sidewall, a large gash or a tire that came off the rim.

How to use the kit safely

1. Park on firm, level ground with the hazards on.
2. Read the kit's label and the owner's manual first.
3. Leave any nail in place unless the kit says otherwise.
4. Connect the sealant and pump as shown, then inflate.
5. Drive slowly to spread the sealant, then check the pressure.
6. Keep to the kit's speed and distance limits.

USTMA says drivers should follow the car maker's instructions, including any reduced speed limits on the drive to a tire shop.

Does sealant damage the tire?

It can. USTMA says aftermarket sealants are not proper repairs and may damage the tire, void its warranty, or harm the pressure sensors inside the wheel.

Some shops can't repair a tire full of sealant, or need to clean it all out first. Check the kit maker's instructions on what happens next.

• Always tell the tire tech the tire has sealant in it.
• Some sealants are flammable, USTMA warns. Never add your own chemicals.
• Replace the kit's sealant bottle once used, or when it expires.

What about run-flat tires?

Run-flats let you keep driving a short distance at reduced speed after losing air. Your owner's manual gives the exact distance and speed.

USTMA says run-flat tires have their own repair rules, which vary by car and tire maker. Many can't be repaired after running flat.

Don't mix one run-flat with normal tires except briefly in an emergency, says USTMA.

USTMA also says a working tire pressure monitor must be used with run-flat tires. A run-flat can feel almost normal with no air, so the dashboard light may be your only warning.

• When the light comes on, slow down and check each tire.
• Find the run-flat limits in your manual before you need them.
• Plan the shortest route to a fix, not the rest of your day.
• Replace run-flats with run-flats, in the size your car maker lists.

Run-flats are often harder to find on a weekend, so start looking early.

Mobile tire service or a tow?

A mobile tire service fixes it where the car is, so there is no tow and no waiting room. A tow makes sense if the wheel is damaged or no tire in your size is available.

With a mobile service, a tech brings a new tire in your size and fits it at your home, work or the roadside. You get the all-in price by text before anyone drives out. See mobile tire replacement.

If the tire only has a small hole in the tread, it may be repairable. USTMA allows repairs only in the tread area, for holes up to 1/4 inch, with the tire off the wheel. See tire plug vs patch and flat tire repair.

How do you find your tire size?

Read it off the side of the tire, or from the label inside the driver's door. It looks like 225/65R17, often followed by a load index and speed letter.

USTMA says the label is usually on the driver's door edge or doorpost, in the glove box or inside the fuel door. The owner's manual lists it too.

• Take a photo of the sidewall where the size is printed.
• Take a photo of the door label as well.
• Note if the front and rear sizes differ. Some cars do.

A replacement should match the size, load index and speed rating your car maker calls for. On all-wheel drive, check the manual about replacing just one tire.

What should you have ready when help comes?

The car keys, the locking lug nut key if your wheels have one, and a clear way to the car. Those three things decide whether the job can be done where the car is.

• Lug nut key: check the glove box, console and trunk. Without it, the wheel can't come off.
• Location: the address, the parking level or the nearest exit sign.
• Gate or garage codes: for apartment lots and parking garages.
• Room to work: a car tight against a wall or another car may need to be rolled out.
• Your phone on: the tech may text with a question.

Low parking garages can be a problem for service vans. Say if the car is on a low level, and we work out a plan before anyone drives out.

Next time, a spare may be worth buying. See how long you can drive on a spare for what a donut can and can't do.

When to contact us: No spare and a flat? Send us your details with the tire size and where the car is, and we check the size before we quote.