Fitment Calculator: Calculate ET Value, J Width & Tyre Size Online
WHEELS 'N CUSTOMS
ONLINE CALCULATOR: CALCULATE ET VALUE, J WIDTH & FITMENT
How Does Our Wheels & Tyres Fitment Calculator Work?
When you are considering a new set of alloy wheels or a different tyre size, it is essential to calculate precisely in advance how the new combination compares to your current setup. A deviation in ET value (Einpresstiefe), J width (rim width in inches) or the tyre rolling circumference directly affects the speedometer reading, the clearance around the brake calipers, the strut and the wheel arch edges.
Our online Fitment Calculator compares the old and new situations with millimetre accuracy and instantly generates a visual representation. This helps you avoid your new setup rubbing against the inside of the shock absorber or, conversely, sticking out too far beyond the bodywork. The question is: Will They Fit?
Interactive Wheel & Tyre Fitment Calculator
Enter the current specifications of your wheels on the left and the desired new setup on the right. The results and the graphic illustration are updated live automatically:
Current Setup (Old)
New Setup (New)
Inner Clearance (Shock absorber)
3.7 mm
More clearance
Outer Position (Wheel arch)
16.3 mm
Further outwards
Graphical cross-section visualisation (Black = Old | Red = New)
Calculated position change & fitment results:
Inner clearance: Calculated...
Outer position: Calculated...
Speedometer deviation: Calculated...
Wheel arch fill: Calculated...
The Crucial Factors for a New Wheel & Tyre Setup
1. The ET value (Offset)
The ET value indicates in millimetres how far the mounting face sits from the wheel centreline. A lower ET pushes the wheel further out towards the wheel arch; a higher ET pulls the wheel further inwards.
2. The rim width (J value)
When you choose a wider rim (for example from 8.0J to 8.5J), the rim increases on both sides by half the difference (0.25 inch on the inner and outer side).
3. Rolling circumference & speedometer reading
For the APK and safety systems (ABS/ESP), the tyre’s overall rolling diameter may not deviate by more than +1.5% or -2% from the factory specification.
100% Fitment Guarantee at Wheels 'N Customs in Nijkerk
Unsure about the result of your calculation, or have you fitted a lowered suspension/Big Brake Kit? Let our fitment specialists verify the exact fitment. We install your wheels, tyres, lowering kits and wheel spacers professionally and without scratches in our workshop in Nijkerk.
Our wheel and tyre specialists are happy to work out the perfect fitment for your vehicle with you.
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