Tyre and wheel calculator
Compare tyre and wheel sizes and see before you buy whether they fit: draw in the fender edge or wheel arch and place a photo of your vehicle behind the diagram. Plus outer diameter, rolling circumference, speedometer deviation, track widening and offset – with before/after and original tyres per vehicle type.
Before
After
Cross-section from the front through the standing right wheel: rim (grey) and tyre as separate parts, camber rotated about the contact patch; numbers = distance of the contour inside/outside to the mounting face in mm. Schematic – no guarantee, tolerances of tyres and rims may cause deviations.
Side view
- Before · Ø 632 mm
- After · Ø 634 mm
| Value | Before | After |
|---|---|---|
| Size | 205/55 R16 · 6.5J ET46 | 225/45 R17 · 7.5J ET45 |
| Outer diameter | 631.9 mm | 634.3 mm+2.4 mm |
| Rolling circumference | 1,985 mm | 1,993 mm+0.38 % |
| Sidewall height | 112.8 mm | 101.3 mm |
| Vehicle higher/lower | – | +1.2 mm |
| Speedometer shows 50 km/h, actual | 50.0 km/h | 50.2 km/h |
| Speedometer shows 100 km/h, actual | 100.0 km/h | 100.4 km/h |
| Speedometer shows 130 km/h, actual | 130.0 km/h | 130.5 km/h |
| Track per side (outside) | – | +11.0 mm |
| Space to the strut (inside) | – | -9.0 mm |
| Axle track width | – | +2 mm |
| Rim width for the tyre | 5.5–7.5 J | 7.0–8.5 J |
Guide values without guarantee. Usually the rolling circumference may deviate by at most +1.5 % / -2 % from the registered size; the speedometer must never show less than the actual speed. Vehicle papers (CoC), tyre and wheel approvals (ABE, certificates) and the inspection are decisive. Tolerances of tyres and rims (manufacturer, pressure, load) may cause deviations. Rim width by ETRTO approximation, contour across the width of rim and tyre. Search part certificates and ABE
Save the configuration including fender edge and photos to a vehicle in your garage – please sign in for this. Until then your values stay in this browser.
Share as link
Without signing in: save values and fender edge as a link – without photos. Only accessible via the link; later the configuration can be saved to a vehicle after signing in. Links not opened for 12 months are deleted.
Choose vehicle
Original sizes from the community: counted from registration certificates (without special entries on wheels) and tyre sets marked original or registered – only as a count, without people.
Frequently asked questions
Can I draw in my vehicle’s fender edge?
Yes. Enter the clearance above the tyre and the lateral distance to the outer edge, or drag the edge directly in the diagram – in the cross-section through the wheel and in the side view at the wheel arch. For each variant the calculator shows how much room is left at the top, at the side and at the wheel arch, camber included.
Can I add a photo of my vehicle?
Yes. Place your own photo behind the diagram for each view – from the front onto the fender, from the side onto the wheel arch – and adjust transparency, size and position. That way you see the new wheels on your own vehicle. The photo stays in your browser and is only stored if you sign in and save the configuration to your vehicle.
How much may the outer diameter differ from the original?
As a rule of thumb, about +1.5 % to −2 % compared with the registered size. What counts, however, are the registration documents, the wheel or tyre approval (ABE, parts certificate) and the inspector.
How does a different tyre size affect the speedometer?
A larger rolling circumference makes the speedometer show less than you are actually driving; a smaller one shows more. The calculator shows the actual speed at an indicated 30, 50, 100 and 130 km/h.
What does the rim offset (ET) mean?
The ET (offset) is the distance in millimetres between the rim centreline and the hub mounting face. A lower ET moves the wheel outwards and widens the track, a higher ET moves it inwards.
Do I need to have a new wheel and tyre combination registered?
Sizes not in your papers usually need an ABE or a parts certificate with an inspection under § 19 StVZO. The calculator does not replace an approval, but helps you compare in advance.