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Motoring Solutions — Guides & Advice

Tyre Speed Ratings

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When replacing tyres most of us know it is critical to get the right size. But what about the speed rating — and does it really matter? The RAC covered this in some detail. Most ratings are well beyond anything we will ever drive, so why should anyone care?

A tyre sidewall showing an H speed rating

The Ratings

The rating is the letter at the end of the tyre size, moulded into the sidewall. The common car ratings are:

You may also see ZR in the size on a performance tyre. It is a legacy marking meaning the tyre is rated above 240 km/h, and it normally appears alongside a W or Y rating that gives the actual figure. Read the full marking rather than the ZR on its own.

There are lower ratings than these, but they are unlikely to turn up on a car tyre. The scale is set in kilometres per hour and converted to mph, which is why the steps look uneven — and why H sits above U rather than where the alphabet would put it.

More Than The National Speed Limit

The highest national speed limit in the UK is 70mph on the motorway. But driving in Europe is straightforward now, and some roads there carry far higher limits — parts of the German autobahn network have no limit at all. Matching the tyre to the capability of the car you own is simply common sense.

The Insurance Question

Fitting a tyre rated below the manufacturer’s specification is not automatically illegal. But many insurers treat it as an unapproved modification, and some will argue the car was not roadworthy — which gives them grounds to reduce or refuse a claim even where the tyres had nothing to do with the incident.

Do not let a fitter talk you into a lower rating because it is what is in stock and it is “more than you’ll ever do”. The rating is not really about your top speed; it reflects how the tyre is constructed to handle heat and load. If you are unsure what your car needs, it is on the tyre placard in the door shut or in the handbook, and your insurer will confirm its position in writing if you ask.

Mixing And Matching

Where tyres differ, put the higher-rated pair where the manufacturer says — and never mix different ratings across the same axle. The same goes for load index, which is the number just before the speed letter and matters more than most drivers realise on heavy modern cars, electric ones especially.

More on buying part worn tyres.