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Everything you ever wanted to know about tyres!

Over many years we have experienced many problems that can be traced back to bad tyres or incorrectly fitted/balanced/inflated/aligned tyres. As these round black things are the link between your car and the road we felt that they deserve a web page of their own! Of all the decisions you need to make as a Mercedes owner, the choice of replacement tyre is one of the most important.

As far as I know Daimler AG (the parent company to Mercedes-Benz) has no financial interests in any tyre company in the world. This means that they have no reason to have a bias in their choice of tyre to fit as original equipment on new cars. One thing I do know is that Mercedes-Benz have over 10000 staff in their research and development department. I am sure that there is at least one section responsible for the evaluation of tyres. What all this is leading to is the reason we recommend and sell Continental and Michelin tyres. Go and have a look at your local Mercedes-Benz dealer at the new cars on display. What brand of tyres are fitted? The most common two brands of original equipment tyres are CONTINENTAL and MICHELIN. Other brands used, but not common, are Pirelli and Toyo. So why do the people responsible for tyre selection chose Continental and Michelin over all the other tyre companies in the world? It's not because there both German. Michelin is a French company! It is because of the consistent quality and reliability of these two brands. If you want your car to maintain its handling, ride quality and road noise levels chose the tyres that Mercedes-Benz chose.

Continental is the world's fourth largest tyre manufacturer. The company is based in Hanover Germany. Continental currently has 5 plants in Europe, these being based in Sarreguemines in France, Hannover-Stöcken and Korbach in Germany , Portugal and Gislaved in Sweden. The Continental home page can be found here. Original fitment on some of the current E class is the ContiEco Contact CP it is one of Continentals range of environmentally responsible tyres.

Michelin is the second largest tyre manufacturer in the world with annual tyre sales in excess of US $ 12 billion and the market leader in Europe where the Michelin brand has always maintained a premium level and a quality image. The Group is French owned with its international headquarters in Clermont-Ferrand. There are 11 Michelin factories in France plus a number of other sites located throughout Europe, Asia and in the UK, the main UK factory being based at Stoke-on-Trent. There web page is totally awesome! Here is the best place to start. From here choose the best page to look at. There are some great on line games and the history of the Bibendum (the Michelin Man) is most interesting. The Michelin man was first drawn in 1898!

What size?
What size tyres do you have on your car? Have a look in your owner's manual to see what you should have. As I mentioned at the top of the page many of the handling and alignment problems can be tracked down to bad or incorrect tyres. Every Mercedes ever built has been sold with a tyre size that offers the ultimate compromise between: Ride quality, handling, road noise levels, dry grip, wet grip and wear. Remember all those people in the research and development department? The tyre also helps to soften out the ride. So if you have a different tyre size on your car from what the original tyre was you have compromised one of the above points.

If you want to fit larger rims you need to ensure that you don't change the rolling diameter of the tyre as this has a bearing on the speedo reading and on your fuel consumption. To see how this works have a look at this site where they have a great tyre size calculator.

It is our company policy to always fit the original tyre size unless specifically instructed by the owner or in cases where larger diameter alloys have been fitted to only fit tyres that maintain the original rolling diameter.

In Australia retreaded tyres are speed limited to 140kmh! Need I say more. There are many things that concern us about the fitting of retreaded tyres to a Mercedes-Benz (or any other car). Since 1976 most Mercedes-Benz cars have had tyres with at least a S speed rating. Have a look below at the chart and see how the retread compares.

Decoding Tyre Sizes
What's all that stuff on the side of the tyre? All tyres are required to have the size clearly marked on the side wall of the tyre. It will look something like this:

195/65 R 15 91H

So what does it all mean? Well first is the tyre width. In the example above the width is 195mm. This figure refers to the tyre width not the tread width.

The next two numbers are the tyre aspect ratio. In plain terms it would be called the height to width ratio. The above example has a height of 65% of 195mm. ( 126.75mm) If the tyre was a 195/70R14 it would be 70% of 195mm (136.50mm). This two digit figure is referred to as the tyres series. For example "65 series Tyres"

Next is usually the letter "R" This identifies the tyre as having a radial ply construction. If it was the older style cross ply construction it would be identified with the letter "D"

Next is the rim diameter. Our example size was a rim diameter of 15 inches. That's right, "inches". They measure diameter in metric measure and rims in imperial measure!! There have been some attempt to start using rims measured in metric measure but for some reason it never seems to catch on! A tyre with a metric rim has a size that looks like this 220/60 R390.

Finally, comes the load and speed index. This refers to the maximum load and speed the tyre is designed for. Below are two tables explaining the various ratings. Our example is 91H so it is designed to carry 615kg per tyre at a maximum speed of 210kmh.

Speed indexes
The following is a list of speed indexes as found on passenger car tyres. The speed rating is the maximum speed the tyre is designed to work at. A similar set of speed ratings applies for commercial vehicle tyres. Remember back to my comments on retreaded tyres?

R 170kmh 106mph
S 180kmh 112mph
T 190kmh 118kmh
H 210kmh 130mph
V 240kmh 150mph
W 270kmh 169mph
Y 300kmh 187mph
ZR over 240kmh over 150mph

Load Indexes

Remember these are the maximum load for each tyre with the car fully loaded.

75 375kg 88 560kg
76 400kg 89 580kg
77 412kg 90 600kg
78 425kg 91 615kg
79 437kg 92 630kg
80 450kg 93 650kg
81 462kg 94 670kg
82 487kg 95 690kg
83 487kg 96 710kg
84 500kg 97 730kg
85 515kg 98 750kg
86 530kg 99 775kg
87 545kg 100 800kg

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