Reading the numbers on your tyre
Every tyre carries its specification on the sidewall, in a format like 185/65 R15 88H. The first number is the width in millimetres. The second is the aspect ratio, meaning the sidewall height as a percentage of that width. R means radial construction, and 15 is the wheel diameter in inches. The final pair is the load index and speed rating.
Those last two are the ones people ignore and should not. The load index is the maximum weight the tyre can carry, and the speed rating is the maximum speed it is built to sustain. Fitting a tyre with a lower rating than the manufacturer specified is both a safety problem and, in the event of a claim, potentially an insurance one. Going higher is harmless but rarely worth paying for.
You will also find a four-digit date code, usually inside an oval, reading something like 2224. That means the twenty-second week of 2024. Rubber ages whether or not it is used, and a tyre more than five or six years old should be treated with suspicion no matter how much tread remains. Always check this on tyres sold as new: old stock is common and heavily discounted for a reason.
When tyres genuinely need replacing
The legal minimum tread depth 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 finished. In practice, wet grip degrades sharply below about 3mm, so replacing at 2 to 3mm is the sensible call rather than running to the legal limit.
Tread depth is not the only reason to replace. Sidewall bulges mean the internal structure has failed, usually from a pothole impact, and that tyre can burst without warning. Cracking between the tread blocks indicates age hardening. Any of these justify replacement regardless of how much tread is left.
Uneven wear is a diagnosis rather than a verdict. Wear on both outer edges means chronic underinflation. Wear in the centre strip means overinflation. Wear on one edge only points to an alignment problem, and feathered edges you can feel by running a hand across the tread usually mean a toe setting that is out. Replacing tyres without fixing the cause simply consumes the new set the same way.
Alignment, balancing and rotation are three different jobs
These get conflated constantly, and workshops are not always careful about explaining the difference. Wheel alignment adjusts 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 what prevents tyres scrubbing themselves away at the edges.
Wheel balancing is about weight distribution around the rim. Small lead or adhesive weights are added to counteract heavy spots. Imbalance shows up as a vibration through the steering wheel at a particular speed, typically 80 to 100 km/h, and it gets worse the faster you go. Balancing is done every time a tyre is fitted, and again if a weight is thrown.
Rotation is simply moving the tyres between positions to even out wear, because front tyres on most cars wear faster than rear ones. Doing it every 10,000 km or so meaningfully extends the life of a set. None of these three substitutes for the others, and a workshop that responds to a vibration complaint by doing an alignment has not addressed it.
Buying tyres without overpaying
Tyre pricing is unusually opaque because the same size spans a wide quality range. A budget tyre and a premium one in 185/65 R15 can differ by a factor of two. The difference is real and shows up mostly in wet braking distance and tread life, but the premium is not always worth it on a car that does 8,000 city kilometres a year.
What is worth insisting on is replacing in pairs at minimum, fitted on the same axle. Mixing tyres of substantially different tread depth or grip across an axle affects braking stability. Fitting a single new tyre alongside a worn one is acceptable only as a temporary measure.
Check what the quoted price includes. Fitting, balancing, a new valve and disposal of the old tyre should all be part of it. Being quoted a low per-tyre price and then charged separately for each of those is a common way to make a number look competitive when it is not.
