Rims: The ET explains
The shape, color and size of the rims can greatly influence the overall impression of the vehicle. The accessories market offers a seemingly endless selection of suitable rims for every common vehicle model, often with different technical specifications. One of the most important entries for the accuracy of fit of the new dream wheels is the so-called offset, or ET for short.
What the offset means
In order for a rim to sit optimally in the wheel arch, it is usually necessary to position the wheel flange, i.e. the contact surface on which the rim is screwed to the vehicle, slightly off-center to the longitudinal axis of the rim. This deviation is indicated as “ET” in millimeters.
If the wheel flange is exactly in the middle of the longitudinal axis of the rim, the offset is designated with ET0.
However, if the wheel flange is offset, for example, 20 millimeters to the outside of the rim, this would be characterized by an offset of ET20. The larger the offset is selected, the further the rim protrudes into the wheel arch towards the center of the vehicle, and the track becomes narrower.
However, as soon as the contact surface is offset further into the inside of the rim, viewed from the longitudinal axis, there is a negative offset, in the example rim with a deviation of 20 millimeters, i.e. ET-20. With a negative offset, the track widens because the rim is offset outwards by the negative offset.
The correct offset depends on the vehicle
When choosing the offset, the rim width is the decisive factor. Basically, the greater the width, the smaller the offset, so that the wheel does not rub against parts of the chassis or the suspension.
However, if the rim is too wide or the offset is too small, the wheel could rub against the edge of the fender or even protrude over the fender.
In order to avoid such extreme cases, the manufacturer usually provides lists of which rim / tire combination is suitable for which vehicle. As a first clue, a look at the vehicle registration document can also help, where the permitted rim widths are often listed.
The rims currently installed can also provide useful data:
The indication of the offset is usually stamped into the inside of the rim, so conclusions can be drawn about suitable accessory rims with the combination of the standard ET and rim width.
The perfect rim has the wrong ET
It is very annoying if, when researching the rim of your choice, it turns out that it is not available with the right offset for your vehicle.
If the ET is too high, so-called track plates can help. These are flat metal disks that are mounted between the wheel flange of the rim and the contact surface on the car. The offset of the rim is thus reduced by the thickness of the track plate. For example, if an ET25 is required for the vehicle, a rim with an ET30 can be reduced to a suitable total offset of ET5 using a 25 millimeter thick track plate.
If, on the other hand, the ET is too low, the rims can only be fitted by making modifications to the body, such as flanging or widening the fenders.
In any case, prior to an individual adjustment by means of track plates or body widening, a TÜV expert should be consulted as to whether the available reports entitle the holder to be registered by individual acceptance.
Toe-in - what is it?
You know a lot about cars, but you don't know exactly what the individual terms mean? You don't understand what a toe-in is, but you are looking for an explanation? Then you are exactly right here. In this short article we will explain what toe-in is, how it works and should be set, and what you should pay attention to.
Measured on the rim horns, the total track of the vehicle axle is determined with the following difference. The distances between the front and rear wheels to the axle are measured here. The toe is now measured with modern wheel aligners in angular minutes instead of millimeters, which means that the value is not only related to the rim diameter. The angle of a wheel in relation to the length of the vehicle is referred to as a single track. However, this only applies to the rear wheels; the front wheels are measured in relation to the geometric travel axis. You should know that running the bike in a straight line has the least tire wear. The forces that arise on the wheels of your vehicle push forward outward because of the elasticity in the wheel suspensions. This is why your wheels wear off prematurely on the inside. In order to keep your wheels durable, they are set to toe-in on non-driven axles.
What does that mean for rear-wheel drive vehicles?
The lane generally has an immense influence on the driving behavior of your vehicle. Toe-in is the angle between the wheels on an axle. If the wheels of your vehicle are parallel to each other on the axle, they have 0 degrees toe-in. If the front ducks are close together for your speech, i.e. the rear ends, then your car has toe-in.
How exactly does the toe-in adjustment work?
The straight-line stability of your vehicle is the result of the fact that the two front wheels do not steer independently, but that the opposing steering forces of the left and right front wheels balance each other. When toe-in, the right wheel of your vehicle steers a little to the left and the left wheel a little to the right. You should not use a lot of toe-in on very uneven roads, otherwise wear and tear increases immensely. Since one wheel often has better contact with the ground than the other on an uneven road, the steering influence of this wheel is much stronger. In this case, your vehicle will no longer run properly in a straight line, as the precession of the straight line leaves a lot to be desired. This can be very problematic for you if, for example, you want to overtake on a narrow straight and your track is very uneven. In this case, your car drives fairly straight ahead, but, as already mentioned, there is no precession. It is the same when driving on non-slip routes. Here, too, you should refrain from using a lot of toe-in, as the steering forces consume too much of the forward drive force. This means that the top speed of your vehicle will decrease.
You should therefore avoid toe-in on rough or grippy roads, as this can have a huge impact on driving quality and your driving pleasure will suffer. The longevity of your vehicle is also neglected, as the wear on tires and wheels is increased enormously.
How do you read the information on tires?
Every car driver has to deal with the tires of his vehicle sooner or later. If you take a closer look at this, you will find that various information can be found there. But how do you read the information on tires correctly? You can find the answer to this question here.
You can find this information
If you look at your tires, you will quickly find a lettering with the name of the manufacturer. You will also find a combination of numbers and letters. This begins with a three-digit number followed by a slash and another two-digit number. This is followed by a letter, a two-digit number, a two- or three-digit number and another letter. You will also find another sequence of numbers and an E-mark on the tire wall.
On some tires you can also find an alpine symbol with the letters M + S. There may also be an arrow on the tire.
This is what the individual characters mean
The lettering with the name of the manufacturer has no further meaning.
The individual sections of the combination of numbers and letters refer to different information. The first three-digit number indicates the tire width in millimeters.
The following two-digit number indicates the ratio of tire width to tire height in percent. A low percentage indicates a thin tire.
This two-digit number is followed by a letter. This stands for the type of tire. As a rule, there should be an R for radial tires. If the R is followed by an F, it is an emergency tire. In the case of classic cars, it can also be a D for diagonal tires. It is essential to note that, as a rule, all installed tires must be of the same type. Of course, this rule does not apply to the emergency bike.
The first of the two subsequent two-digit numbers indicates the diameter of the rims in inches.
The second is a key figure for the tire's load index. With this, the maximum permissible load of the individual tires can be determined using a load index table. You can see from your vehicle registration document which minimum load the tires you are using must have.
The last letter of this combination stands for the maximum permitted speed. Using a special table for the speed index, you can determine the maximum speed permitted for the tire with the help of the letter.
The sequence of numbers on the tire wall indicates the DOT number. You can see the tire's production year using the last four digits. The first two digits indicate the week and the last two digits the year of production.
The E-mark is purely a security feature. Every tire that is mounted on vehicles with a permitted speed of over forty km / h must show this test mark.
The arrow on some tires indicates the direction of rotation. It serves as an aid in fitting the tire.
The alpine symbol with the letters M + S indicates tires that are also permitted in mud and snow.
Where is the DOT number?
The so-called DOT number can be found on the outside of the tire wall. The abbreviation “DOT” stands for “Department of Transportation” and, in simple terms, describes the date of manufacture of the tires.
The first two digits indicate the week of production and the two last digits the year of production.
For example, if a tire has the imprint “DOT 1514”, it means that the tire was manufactured in the 15th calendar week of 2014.
Nothing lasts forever and that is also the case with car tires, which is why tires should be replaced after 8 years.
The age of the tires can therefore be easily identified from the DOT number!
The origin of the DOT number
The United States Department of Transportation introduced the so-called DOT number back in the 70s.
Over time, the DOT number has become the standard and can now be found on all tires.
The “DOT” is made up of four parts, so you can read off the factory abbreviation as well as the tire size and the production period.
With the help of this number you can see when and where the tire was produced.
With some tires it happens that the DOT number consists of only three digits.
In this case you know that the tire was manufactured before the year 2000, only the last of the three digits indicates the year of manufacture of the tire.
For example, if the DOT number “346” is printed, this indicates a production date in 1986 or 1996.
The age of the tires
It doesn't make a big difference whether tires are used permanently or stored for a longer period of time.
Over time there are also signs of age on stored tires, which are caused, for example, by light and heat.
If the place where the tires are stored is too light or too warm, this can affect the premature aging of the tires.
Premature aging is noticeable through cracks or porous material.
If you store your tires without rims, then it is ideal if you store your tires upright.
However, tires with rims can also be stacked on top of each other, whereby tires without rims should be turned over once a month.
Moisture is also not so well tolerated by the rubber of the tires and causes the tires to age faster.
The most important factor in terms of tire safety and drivability, however, is the tread depth.
The technical condition of the tires should also be checked from time to time.
The abrasion of the treads, the strength and regularity of the load and different temperatures have the greatest effect on the tires.
Even if the material (the rubber) of the tires usually lasts for more than 10 years, tires have to be replaced beforehand due to the defective tire profile.
When should tires be replaced?
As a rule, experts recommend replacing the tires after 10 years at the latest, this applies to both summer and winter tires.
However, tires can age much earlier, as you can see from the examples above.
It is therefore recommended that six-year-old tires be checked regularly for damage and cracks.
Using the DOT number, you can see exactly how old the tires are!