Questions, answered.

No. Checking a size, reading a sidewall and the tyre label are free and need no account, and nothing you type is kept. Only the garage, which keeps your cars and tyres for you, needs one — and that is free too.

On the drivers' page, in the box under "Check my size". Type it as it is written on the tyre's wall, like 205/55R16, and the answer appears straight away: how wide the tyre is across the tread, how tall the sidewall is from the rim to the tread, how big the whole tyre is, and how far one turn of it carries the car.

Yes. Press Imperial above the answer and every figure is shown in inches; Metric puts it back. The page remembers which you chose.

Under the answer, "What else fits" lists other sizes that go on the same rim, each with a verdict in words and a colour: green for a swap within the usual tolerance, yellow for one that is borderline, and red for one that is outside it. The verdict is about how much bigger or smaller the whole tyre is, because that is what changes your speedometer and how the car sits.

It is a guide, not a fitting. Before you change size, ask the shop that fits it, and check what your car's maker allows.

On the tyre's wall, in raised letters, in a line like 205/55R16 91V. It is the same on every make of tyre. Your car usually also has a sticker with the sizes it was built for, inside the driver's door or the fuel flap.

How to read a tyre sidewall shows an example, part by part: touch any part to see what it means.

• 205 is the width across the tread, in millimetres.
• 55 is the height of the sidewall, as a percentage of that width. Here, 55 per cent of 205.
• R16 means a radial tyre for a 16-inch wheel.

A tyre with the same three numbers fits the same wheel, whoever makes it.

The two after the size, like 91V. The number is the load index: the most weight each tyre is built to carry, and 91 is 615 kg. The letter is the speed rating: the fastest the tyre is built to run at, and V is 240 km/h.

A new tyre should carry at least the load and speed your car was built for. Lower figures than the ones on your car now are a question for the shop before they are fitted.

Look for the letters DOT on the wall. The last four digits of the code after them are the week and the year it was made: 2219 is week 22 of 2019.

Rubber ages whether it is driven on or not. The garage reminds you to have a tyre checked at six years old, and says plainly to replace it at ten.

A place to keep your cars and the tyres on them: the size, the make and pattern, when each went on and how much tread it had. Every tyre's details and label grades are filled in for you, so you type the size and the brand rather than the specification.

It also tells you when something is due: tread getting low, a tyre getting old, a pressure check, and, where your country changes tyres for winter, the swap.

Yes. The example garage is a made-up driver's garage, with a car, a spare and tyres in storage. It opens straight away with nothing to type, and nothing you do in it is kept.

On My garage, with where you drive, your name, an email address and a password of at least twelve characters. We send a link to that address, and the garage opens when you press it. It is free, and there is no card to enter.

We will email you when a tyre needs attention. You can turn that off under Settings in your garage, or with one tap on any reminder.

Yes. Checking a size, reading a sidewall and the tyre label need no account, the garage is free with one, and none of them is going behind anything a dealer pays for.

They are also not charity. A driver who knows what the car takes walks into a shop knowing what to ask for, and that is the whole reason they exist.

When the lowest tread reading you add is under 3 mm, the tyre's card says "replace soon", in yellow: wet braking gets noticeably longer from there. Under 1.6 mm, the legal limit in most places, it says it is below the limit, in red.

By age, from the DOT date: "check it" at six years old, and "replace it" at ten.

Yes. Each card of tyres in a garage says which season they are for: summer, winter or all-season. If the tyre carries the snowflake-on-a-mountain mark, the garage starts them as winter tyres, unless the name says all-season; you can change it in Edit either way. Winter and all-season tyres are labelled that way on their card, wherever they are — on the car or in storage.

Tyres in storage can also say where they are kept, in your own words — In the garage, At the tyre shop, bay 3 — and the card shows it. It is for you, and no shop sees it.

Yes. Give a car a nickname — My Corolla, the white bakkie — and a colour, in Edit. The card shows the nickname, with the car's year, make and model under it, and the car is drawn in its colour. The number plate is there too, and only you see it.

The garage counts every tyre: two on the front, two on the back, the spare and four winter tyres in storage are nine.

Your car from above, with each tyre where it sits: green when it is fine, yellow when it is due soon, red when it needs replacing, grey before its first tread reading. The lowest tread is written on each tyre. Tap one to open it. If you prefer a list, press List.

Anything that needs replacing now is also in a red "Needs attention" box at the top of the garage, with the tyre it is about.

Yes, free, on each car: when the licence runs out, when the next service is due by date or reading, and the wheel-lock code. The licence is called by your country's word for it: licence disc, vehicle tax, rego.

They are kept on your account, so they follow you to any phone you sign in on. When the licence or the service is a month or 1 000 km away, it shows under "What is due" and comes in your emailed reminders. The wheel-lock code is locked away: it shows only when you press Show, only to you, and never appears in a reminder.

Yes: of the car, of yourself, and of each tyre as it wears. Tap the car's drawing for its photos, open a tyre for its own, and add yours under Settings. Each photo is kept on your account and only you can open it. A photo larger than about 1 MB is refused with a message. Phone photos are made smaller before they are sent, so this is rare.

Yes, free, on each car. Add a fill-up with the date, the odometer, the litres, what you paid and whether you filled the tank. From one full tank to the next, the garage works out how much fuel the car uses (L/100 km, or miles per gallon where you drive in miles) and what it costs you per kilometre. It also shows your last fill-ups and what you spent on fuel this month.

Yes. Under "Tread and pressure", tap a tyre, set its pressure with − and +, and set its tread with the three sliders. Press Save and the readings are kept on that tyre, dated today. In the example garage the same panel is there to try, and nothing is saved.

With your own garage, everything you add is on your account: cars, tyres, readings, photos, notes and the fuel log. If an earlier version of the garage kept your notes or a car photo on this phone, the garage asks once, "Keep these on your account?". Yes moves them. Not now leaves them on the phone.

The example garage keeps nothing anywhere. What you try in it stays in the page and is gone when you leave, and none of it is sent to us.

Three things, each graded so tyres of the same size can be compared:

• Fuel: how much the tyre holds the car back as it rolls. A better grade uses less fuel.
• Wet grip: how well it stops on a wet road. A better grade stops shorter.
• Noise: how loud it is on the road outside the car, in decibels.

Read a tyre label, grade by grade goes through each one.

Shops that sell new tyres show it where the law asks them to, and the maker publishes it. In the garage, your tyres' grades are filled in for you, so you can see the label for the tyres already on your car.

Not yet. Find a shop is coming. Until it is here, take the size you checked to the tyre shop you trust: the size is all any shop needs to know to fit the right tyre.

No. No shop sees your garage unless you ask one to. What you keep in it, the number plate included, is for you.

Yes, each with one press, under Settings in your garage, in "Your data": Download everything gives you a copy of all of it as a file: your cars, tyres, readings, notes (the wheel-lock code too), fuel log and photos. Delete everything removes all of it from your account, and from this phone. It is yours, and no shop sees it.

Very little, and the full answer is on its own page.

Measurement here is cookieless by default. Google Analytics runs only if you say yes to it, and nothing loads until you do — an unanswered banner is a refusal rather than a maybe.

See the privacy page for the whole of it, which is one page for the entire estate rather than a different one per module, and the cookies page for exactly what is kept in your browser.