ET Rim Calculator
When comparing rims, the reference point is the REFERENCE RIM. This is the currently installed rim on the car. Knowing its parameters, we can determine the location of the NEW RIM in the wheel arch down to the millimeter. If you don't know what width and offset your current aluminum rims have, you can check it on the inside of the rim by removing the wheel. The parameters will be stamped on one of the spokes of the rim. In the case of steel rims, the parameters are located on the front.
What is the ET parameter? This is the distance of the mounting surface of the rim to the hub from the vertical axis of symmetry of the rim, expressed in millimeters. To put it very simply - the lower the ET, the more the rim will protrude towards the outside of the vehicle. Please remember that when positioning the rim in the wheel arch, you also need to take into account its width. To sum up - knowing the two basic parameters of your current and new rim, i.e. their width and offset ET, we are able to compare them and thus find out how much more or less the new rim will be extended and how much closer or farther it will be from the suspension elements and calipers brakes.
How to know whether the new rim will not protrude beyond the outline of the car? Just measure the distance of the current rim to the outline of the car. The point that determines the outline of the car is the upper edge of the fender. Just place the level on the wheel. We check whether there is enough space in the wheel arch. Moving the rim outwards by 10 mm - 15 mm is a safe margin (does not apply to super sports cars such as the Audi RS or BMW M5).
You should also remember about the inside of the rim. If it gets too close to the inside of the car, it may rub against the brake caliper, shock absorber or other suspension components.
We invite you to use the ET calculator, which will certainly present all this in the best possible graphical way. Just enter the details of your current and new rim from our website. Don't forget to take into account distances if used.
DESCRIPTION OF PARAMETERS
Width : measured between the rim flanges. The dimensions are given in inches. The manufacturer usually places it on the inside of the rim.
Weaning ET: this is the distance of the mounting plane from the rim's axis of symmetry. ET is given in mm. The service book or ASO only provides the parameters of the currently installed rims.
Spacer : mounted to the wheel hub. It increases the wheel track on a given car axle. Dimensions given in millimeters.
Read more on the LadneFelgi.pl blog
Result
From the outside (rim front)
The new rim will be mounted in the same way as in the case of the standard rim.
The new rim will be 12.4 mm deeper than the standard rim.
The new rim will protrude 12.4 mm more than the standard rim.
From the inside (back of the rim)
The new rim will be mounted in the same way as in the case of the standard rim.
The new rim will be 12.4 mm further from the suspension components than the reference rim.
The new rim will be 12.4 mm closer to the suspension components than the standard rim.
