Most people only look at their tyre size when a fitter asks for it over the phone, and then it’s a walk to the car park with a phone torch. It’s worth knowing what the numbers mean, though. Get one of them wrong and you can end up with a tyre that goes on the rim but rubs the wheel arch, throws your speedometer off, or isn’t built to carry the weight of a loaded family SUV.
Take a size you’ll find on plenty of Corollas, Elantras and Golfs: 205/55 R16 91V. Every part of it is telling you something.
01Where to find your size
It’s moulded into the sidewall of every tyre in raised letters. The size your car left the factory with is also printed on a sticker inside the driver’s door frame, and on some cars inside the fuel flap or the glovebox lid. If the sticker and the tyres on the car don’t match, trust the sticker, unless you know a previous owner changed the wheels.
02Width, profile and rim
205 is the width of the tyre in millimetres, from one sidewall to the other. Wider isn’t automatically better. It gives a bit more grip in the dry, but the steering can feel heavier at parking speeds and the tyre usually costs more.
55 is the profile, also called the aspect ratio. The sidewall is 55% as tall as the tyre is wide, so roughly 113 mm here. A lower number means a shorter sidewall: sharper steering, a firmer ride, and less cushion for the rim when you catch the edge of a speed bump or a pothole. SUVs on 65 or 70 profile tyres ride softer for exactly that reason.
R means radial construction, which is what nearly every car tyre sold today uses. 16 is the rim diameter in inches, and this is the one number that isn’t negotiable. A 16-inch tyre only fits a 16-inch wheel.
Some 4×4 tyres use a different format, like 31×10.50 R15. There the first figure is the overall diameter in inches and the second is the width in inches.
03Load index and speed rating
The 91V on the end is easy to ignore, and it shouldn’t be.
91 is the load index, a code for how much weight each tyre can carry at the correct pressure. 91 works out to 615 kg per tyre. A mid-size SUV will typically need 100 or more, and vans use commercial tyres with a C after the rim size.
V is the speed rating, the top speed the tyre is designed to sustain: 240 km/h for V. H is 210 km/h, W is 270 and Y is 300. Nobody is doing 240 on Sheikh Mohammed bin Zayed Road, but the rating also says something about how well the tyre handles heat build-up, and that counts on a 46-degree afternoon. Never fit a lower load index than your car’s placard shows, and it’s sensible not to drop below the original speed rating either.
04The other letters on the sidewall
XL (Extra Load) means a reinforced tyre that carries more weight at a higher pressure. Run-flat tyres carry codes like RFT, ROF, SSR or ZP depending on the brand; our piece on run-flat tyres goes through them. Codes such as AO, MO, ★ or N0 mean a car maker approved that tyre for its models, and our guide to car-maker tyre markings explains each one.
You’ll also find a four-digit date code after the letters DOT. That’s the week and year the tyre was made, and in this climate it matters. Here’s how to read the DOT date.
05Can you change to a different size?
Within limits, yes. Fitters often move a car to a slightly different size, for example a bigger rim with a lower profile, as long as the overall diameter of the wheel and tyre stays within about 3% of the original. Go further than that and the speedometer, ABS and stability control are all working from the wrong numbers, and the tyre may touch the arch at full steering lock.
If you want to see what fits, our tyres by car pages list the factory sizes for each model and generation. Or send us your current size on WhatsApp and we’ll tell you what else is safe to fit.
Once you know your size, the rest is easy. Pick it in the size finder, or go straight to a size page like 205/55 R16 to see every tyre we have in it, with the fitted price shown upfront.