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Safety, comfort, and driving pleasure: Tires should offer all of this. But when is it time to buy new? And which tire is the right one? Everything you should definitely consider when buying.

  • Change? Depends on tread and age
  • The right tire dimension

What do motorists value most when buying tires?

For the vast majority, good grip on wet roads as well as good braking and steering behavior and maximum load-bearing capacity even in extreme situations are the most important factors when buying a tire. If driving comfort and price are also right – great.

But which tire is the best? Can it be an all-season tire? What size fits my car? And when do I have to change? We give tips.

Change tires? Depends on the profile

The legal situation is clear: as soon as your car tires have less than 1.6 millimeters of residual tread, you are no longer allowed to drive on the road with them. The tires are no longer considered roadworthy and must be sorted out. If you are caught in traffic with worn out tires, you will be fined.

 

New Tire Tests Show the Quarter Is the New Penny

In the old Penny Test, seeing the top of Lincoln’s head while holding a penny upside down in a tire tread groove indicated a tread depth of 2/32-inch (1.6mm) or less, and that the tire needed replacing.

However, extensive Carnes tests with different tread depths have proven this: The legally defined tread limit offers only a residual amount of safety. For summer tires, the tread depth should be at least three millimeters, for winter or all-season tires at least four millimeters – otherwise it becomes critical in wet, snow or slush.

By the way, if only one or two tires are worn or broken, you should always replace them by the axle, i.e. always replace at least two tires.

If all tires have the prescribed dimensions, you can also combine models from different manufacturers. However, we recommend that you stick with one model. The tires with the better tread must be placed on the rear axle, this way the car will be stabilized. Read more: Best Tires For Mazda 3

Problem: Tire aging

Tires also “age” – so they should not be driven indefinitely. This also applies if the remaining tread depth is significantly above the legal minimum tread depth. Background: The rubber compound of the tire hardens over time, which worsens grip and braking distance in the wet.

This is particularly evident with winter tires, which must remain “soft” even at low temperatures. They already lose some of their winter properties from around six years of age, which is why we tend to advise against using winter tires that are older than eight years. Summer tires should also not be older than eight to ten years.

It is therefore important that the tires are as young as possible when they are purchased. Due to the large number of tire formats, it is possible that the tire was not produced in the last few months when the retail trade rationally stocks the tire. But it should not be older than two years – you can point this out when placing your order.

The production date of the tire is read on the sidewall. The last four digits of the multi-digit DOT number indicate the production date. If it says “1318”, for example, this means that the tire was produced in the 13th calendar week (KW) 2018.

how to choose tires tire specificationsSummer, winter or all-season tires?

Just a few years ago, things were clear: in summer, the summer specialists came onto the car, and with their grip-resistant compound, they don’t let up even in hot temperatures. And in winter, the finely treaded winter tire was first choice, with its sipes that are frost-proof and interlock perfectly even on slippery roads.
But in the meantime, more and more manufacturers, who previously held back with the actual or supposed all-rounders, are coming onto the market with products for the whole year. The demand for all-season tires is rising continuously: the share of all-season tires among all passenger car tires sold has now risen to more than 15 percent.

Based on the Carnes test results for all-season tires, however, the following must be considered when using them as a replacement for summer and winter tires: All-season tires remain a compromise that cannot match the performance of good specialists for summer and winter.

With the exception of individual models, all the all-season tires tested show more or less clear weaknesses on dry roads, which are fully loaded and become even worse in midsummer temperatures. However, the weaknesses on snow are particularly evident in the latter case. Read more: Best Tires For Ford F350 Super Duty

Tire Repair

In many cases, car and motorcycle tires with puncture wounds can be repaired in a qualified specialist company. However, it is up to the respective tire manufacturer to decide whether to exclude individual models in his product groups from the repair option or to make special repair specifications. Most punctures in the tread area (in motorcycles only in the middle area of the tread) with an expansion of up to 6 mm can often be repaired by means of warm or hot vulcanization.

Which dimension is the right one?

Which tire sizes are approved for the vehicle can be seen from the information in lines 15.1 and 15.2 of the “Registration Certificate Part 1”. Only one size or a combination of sizes is entered here if different tire dimensions are provided on the front and rear axle. Further approved tire dimensions are contained in the so-called chain of custody, which every buyer receives when purchasing a vehicle (see below).

In the “old vehicle registration document” issued up to 2005, the tire sizes can be found under numbers 20 and 21 or 22 and 23. Under number 33, further information on additional rim/tyre dimensions and the use of snow chains is often entered.

And this is how you read the information on the tires that are already fitted: The inscription 245/45 R 17 91 H in our example picture means the following:

The number at the beginning indicates the tire width in millimeters. Our example tire is therefore 245 millimeters wide.

/45 explains the ratio of height to width of the tire cross-section in percent. A /50 would mean that the tire is half as high as it is wide.

R denotes the type of tire construction: R stands for radial, the type of tire construction commonly used today.

15 denotes the rim diameter in inches.

91 is the key figure for the load capacity of the car tire. 91 stands for 615 kilograms.

In the last place is the speed symbol, which indicates the maximum permitted speed of the tire. H means a maximum speed of 210 km/h.

By the way, for winter tires marked with M+S (manufactured before 2018) or the Alpine symbol (in the picture: snowflake in a three-toothed mountain), the speed index may be lower than the value for the maximum vehicle speed. In this case, a sticker in the field of vision must remind the driver of the lower maximum speed. Alternatively, a speed limiter with a corresponding display can be set.

If you have a newer car, a tire pressure control system is probably installed. The air pressure is permanently measured either indirectly via the ABS sensors or directly via sensors which are often located in the valve of the rim. Read more: Best Tires For Subaru Legacy

Do you want it to be a little wider?

The tire sizes entered in the registration certificates do not have to correspond to the actual tire dimensions mounted. But if you want to change over to wide tires, be aware of the following: although they look better and offer more grip on dry roads, aquaplaning occurs more quickly in wet conditions. Driving comfort is impaired and fuel consumption increases.

The principle of wide vs. narrow is illustrated by a current comparative test of winter tires with different widths in dimensions ranging from very narrow (195/65 R15) to very wide (225/40 R18). On snow, narrow tires have advantages when starting off. The lateral guidance when cornering is also better. The risk of aquaplaning in wet and slush is also lower with narrow tires: Extra-wide winter tires float up much earlier than narrow ones.

In the aquaplaning test (water depth 7 mm), the 225 tires lose contact with the road surface already at about 70 kilometers per hour, but the narrow 195 tires only lose contact with the road at well over 80 kilometers per hour.

The wide tire only has advantages in terms of driving safety and steering feel on dry roads. So if sportiness is not so important, the most common tire size for your car is best. Read more: Best Tires For Hyundai Sonata

UHP and run-flat tires

Ultra High Performance (UHP) tires are tires with cross-sections equal to or smaller than series 45 and speed index V, W, Y or ZR. Typical UHP tires have dimensions such as 225/45 R 17 91 W or also 235/30 ZR 19.

Run-flat or run-flat tires are tires that have reinforced sidewalls and do not collapse even when completely deflated, but allow limited continued driving with a maximum speed of usually 80 km/h over a distance of at least 80 km. Some vehicle manufacturers such as BMW and Daimler offer run-flat tires as standard or optional equipment. UHP and run-flat tires have a combined market share of approximately 25 percent of all passenger car tires.

However, fitting these types of tire requires special knowledge, qualifications and tools. You can find tire dealers and installers certified for fitting UHP and run-flat tires here in your area.

Information in the trade: The tire label

Since 2012, tire dealers have been required to affix a so-called tire label to exhibited tires or in the vicinity of tires. For tires not on display, the information on the tire label must be made available to the customer in some other way. In addition, the information contained in the tire label must be shown on the invoice.

The “tire label” should enable the buyer to assess individual characteristics of the tires under consideration and to compare different models with regard to the three criteria listed, which are tested by the tire manufacturers themselves. In contrast to the comprehensive catalog of criteria of the Carnes tire test, only the rolling resistance (top left in the picture), the wet braking properties (top right) and the external driving noise (bottom) are taken into account in the tire label information.

Customers are familiar with this principle from the awards for refrigerators or televisions. The rolling resistance or fuel efficiency of the tires is divided into the classes A to C and E to G. The fuel saving from the best class A to G is estimated at around 7.5 percent for passenger cars. In terms of wet grip, braking distance differences of 30 percent can arise between classes A and F.

Tire test: The right tire, the right brand

The first and most important decision support before the purchase should always be the tire test, since here clearly more safety-relevant criteria are examined. First of all, find out online about suitable tires for your vehicle. In our tests for summer and winter tires (usually the tests of the last three years are up-to-date) you will find all important information and results for the individual models. Is the tire size you are looking for not listed? With restrictions, the test results can also be transferred to “neighboring” dimensions within a vehicle class. This applies to deviations of +10/-10 millimeters in the tire width, i.e. for the tested dimension 175/65 R 14 T these would be identical tire models of the dimensions 165/65 R 14 T or 185/65 R 14 T.

Once your favorite tire is determined, the tiresome search for the best price begins. Because there are no fixed list or base prices for any tire model. In general, each tire dealer negotiates his purchase prices individually with the manufacturer, and whether he passes on any price advantages to the customer or – vice versa – even makes current test winners more expensive is up to him.

A good strategy can also be to buy tires anti-cyclically – i.e. summer tires in winter and winter tires in summer. But don’t just ask on the Internet, but also at local tire dealers for the prices of selected models. They will also tell you what it costs to mount the tire on the rim, to balance it and to mount the wheel. In most cases, you will also have to pay for the disposal of used tires.

David Muench (Carnes Mechanical)

David Muench (Carnes Mechanical)

Hey, I’m David. I’ve worked in a cars store for 6 years. I write reviews and guides, helping people to choose the most suitable technicals and best product for them. I’m happy to finally share my knowledge of the industry here, on CarnesMechanical.

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