How far can you drive on a donut spare?

Go and read the sidewall of the spare that is actually on your car. Temporary spares carry their own speed and distance limits moulded into the rubber or printed on a label on the wheel, and those numbers are the ones that apply to you. Your owner's manual repeats them.

The common restriction is a maximum of 50 mph and a limited range, often given as around 50 miles, but this varies by vehicle and by spare. Do not take a figure off a web page, including this one, as the number for your car. The tire tells you itself.

Why the limits exist

A temporary spare is not a small version of a normal tire. It is a different object built to a different brief: get the car to a place where the real tire can be dealt with, at the lowest possible weight and volume.

It is narrower, so there is less rubber on the road, which means less grip in a corner and under braking, and longer stopping distances in the wet.

It has very little tread and a light casing, so it wears out quickly. Tread on a donut can disappear in a few hundred miles of ordinary use.

It runs at a much higher pressure than a road tire. Around 60 PSI is typical, against roughly 32 to 36 for a normal tire. Check the figure on the spare itself, and check it before you set off, because a spare that has sat in the trunk for six years is usually well down on pressure. A donut inflated to a road tire's pressure is dangerously soft and will overheat.

It is also a different rolling diameter from the other three tires, which brings the next problem.

Things that make it worse than the label suggests

All-wheel drive and four-wheel drive. A different rolling diameter on one corner makes the differentials or the centre coupling work continuously against themselves. On some vehicles that is expensive. Check what your manual says before driving any distance, and if it is not clear, keep the distance to a minimum.

Electronic stability and ABS. These systems compare wheel speeds. A mismatched wheel changes what they see. They still work, but treat their margins as smaller than usual.

Which axle it is on. Some manufacturers require a temporary spare to go on a non-driven axle, moving a full-size wheel from the back to the front if necessary. Again, the manual decides this, not habit.

Weather. The reduced footprint is worst in rain and snow, exactly when you least want it.

Practical rules while it is on

• Treat the speed limit on the label as a hard ceiling, not a target.
• Leave a bigger gap than usual and brake earlier.
• Take corners and highway ramps slower than feels necessary.
• Do not use cruise control.
• Do not tow anything.
• Check the pressure before you move and again if you stop.

Get the real tire dealt with quickly

The limits are the reason to book rather than to plan around the spare. A donut is designed for the trip that ends in the tire being fixed, and the mileage allowance is not meant to be spent on a commute.

This is the straightforward case for a mobile fit. The car is driveable, so it is sitting on your driveway or in a parking lot at work, and the spare is already doing its one job. We come to the car, supply and fit a tire matched to the door placard, balance it, torque the wheel and put the spare back in the trunk.

Bring the damaged tire with you to the conversation, so to speak. If it is a nail in the tread it may be repairable rather than a replacement, which is a large difference in cost. Nail in a tire: can it be repaired sets out the rules, and repair versus replace covers the decision. If it is a replacement, find your tire size tells us what to bring.

When there is no donut at all

A growing share of cars carry an inflator and sealant kit instead of a spare, and some carry nothing. Flat tire and no spare covers what those kits will and will not do, including why sealant can cost you a repairable tire.

Questions people ask

• How far can I drive on a temporary spare? Read the limit printed on that spare's own sidewall or wheel label, and the figure in your owner's manual. A restriction of around 50 miles is common, but it varies by vehicle, so do not assume a general number applies to yours.
• How fast can I drive on a donut? The speed limit is marked on the spare itself, and 50 mph is the usual figure. Treat it as a maximum rather than a cruising speed, and allow longer braking distances.
• What pressure should a donut spare be? Much higher than a road tire, often around 60 PSI, with the exact figure on the spare. Check it before driving; spares that have sat for years are usually well below it.
• Can I use a donut spare on an all-wheel-drive car? Only with care and only for a short distance. The mismatched rolling diameter loads the drivetrain continuously. Check your owner's manual, because some vehicles restrict this heavily.
• Which wheel should the spare go on? Some manufacturers require the temporary spare to go on a non-driven axle, which can mean moving a full-size wheel to the flat's position. Your manual states the rule for your car.
• Can a donut spare be repaired if it gets a puncture? Treat it as a replacement. Temporary spares are not built to be repaired and the repair standards apply to their construction poorly. Get the road tire sorted instead.