Tyre Care 101: Pressure, Tread and Rotation

Four patches of rubber, each roughly the size of your palm, carry the entire weight of the car and every input you give it. Steering, braking and acceleration all resolve to what those patches can do. Tyres are simultaneously the most safety-critical component on a car and the one most routinely neglected.

Pressure is the habit with the highest return

Check pressures every two weeks and before any long drive. Check them cold, meaning before you have driven more than a couple of kilometres, because air expands as the tyre heats and a reading taken after an hour on the highway will be several PSI high.

The correct figure is on a sticker inside the driver door frame, sometimes inside the fuel flap or in the manual. It is not the number moulded into the tyre sidewall, which is the maximum the tyre can safely hold, not what your car wants. This confuses a lot of people and leads to seriously overinflated tyres.

Underinflation is the more common and more dangerous error. A soft tyre flexes more, which builds heat, and heat is what destroys tyres. It also wears the outer edges of the tread, ruins fuel economy, and makes the car feel vague. Severe underinflation at highway speed is the classic recipe for a blowout.

Overinflation is less dangerous but not harmless: it reduces the contact patch to a narrow strip down the centre, which lengthens braking distances, wears the middle of the tread, and makes the ride harsh.

Reading the sidewall

Every tyre carries its specification in a format like 185/65 R15 88H:

• 185 is the section width in millimetres
• 65 is the aspect ratio, meaning sidewall height as a percentage of the width
• R means radial construction
• 15 is the wheel diameter in inches
• 88 is the load index, the maximum weight the tyre can carry
• H is the speed rating, the maximum speed it is built to sustain

The last two are the ones people ignore and should not. Fitting a tyre rated below what the manufacturer specified is a genuine safety issue and can complicate an insurance claim. Going higher is harmless but rarely worth paying for on a normal road car.

There is also a four-digit date code, usually in an oval, reading something like 2224. That is the twenty-second week of 2024. Rubber ages whether it is used or not, hardening and losing grip, so a tyre more than five or six years old deserves scrutiny no matter how much tread remains. Always check this when buying: old stock is common and discounted for a reason.

Tread depth, and when to replace

The legal minimum in India is 1.6mm, and every tyre has moulded wear indicators sitting at exactly that height in the main grooves. When the tread wears flush with those bars, the tyre is legally finished.

In practice, wet grip falls off sharply below about 3mm, because the grooves can no longer clear water fast enough. If you drive through a monsoon, replacing at 2 to 3mm rather than running to the limit is a sensible trade of money against stopping distance.

Tread depth is not the only criterion. Replace regardless of remaining tread if you find:

• A bulge or blister in the sidewall, which means the internal structure has failed, usually from a pothole. That tyre can burst without warning.
• Cracking between tread blocks or along the sidewall, which indicates age hardening.
• Any cut deep enough to expose the cords beneath.
• A puncture in the sidewall or shoulder, which cannot be safely repaired. Only punctures in the central tread area are repairable.

Uneven wear is a diagnosis

How a tyre wears tells you what is wrong elsewhere, and replacing tyres without addressing the cause simply consumes the new set the same way.

• Both outer edges worn, centre fine: chronic underinflation.
• Centre worn, edges fine: overinflation.
• One edge only: a camber or alignment problem.
• Feathered edges you can feel by running a hand across the tread: incorrect toe setting.
• Patchy or scalloped wear: usually worn suspension components or wheels out of balance.

Run your hand across the tread occasionally, not just your eyes over it. Feathering is much easier to feel than to see, and it is an early warning that alignment has drifted.

Rotation, and why it pays

Front tyres on most cars wear considerably faster than rear ones, because the front wheels steer, carry the engine's weight and do most of the braking. On a front-wheel-drive car the fronts also transmit all the power.

Rotating between positions every 10,000 km or so evens that out and meaningfully extends the life of a set. It costs a few hundred rupees and is among the most reliably worthwhile pieces of routine maintenance available. It also means all four tyres reach the end of their life at roughly the same time, which is both cheaper and safer than replacing in a staggered pattern.

Alignment and balancing are different jobs

These get conflated constantly. Alignment sets the angles at which the wheels meet the road, principally toe, camber and caster. It is what stops the car pulling to one side and prevents the tyres scrubbing themselves away at the edges. Potholes knock it out, which in Indian conditions means checking it once a year is reasonable.

Balancing is about weight distribution around the rim, corrected with small weights clipped or stuck to the wheel. Imbalance shows up as a vibration through the steering at a particular speed, typically 80 to 100 km/h, and it gets worse as speed rises. Balancing is done whenever a tyre is fitted and again if a weight is thrown.

Neither substitutes for the other. A workshop that responds to a vibration complaint by performing an alignment has not addressed what you described.

Buying without overpaying

The same size spans a wide quality range, and a premium tyre can cost double a budget one. The difference is real, and it shows up mostly in wet braking distance and tread life. Whether it is worth it depends on your driving: for a car doing 8,000 mostly urban kilometres a year, a good mid-range tyre is a sensible place to land.

Replace in pairs at minimum, fitted on the same axle, and conventionally put the newer pair at the rear for stability. Check that the quoted price includes fitting, balancing, a new valve and disposal of the old tyre, because quoting those separately is a common way to make a number look competitive when it is not.

The spare

Check it. This is the item people discover has been flat for two years at the precise moment they need it. If your car came with a repair kit rather than a spare wheel, check the sealant's expiry date, because it does expire and it is useless afterwards.