Guides: wheels, tyres & TÜV
Every value in the calculator is explained here – with graphics, rules of thumb and TÜV limits.
- 01
Reading tyre sizes: 225/45 R17 91W explained
How to read a tyre size: width, aspect ratio, construction, rim diameter, load and speed index – with graphic and worked example.
Read more - 02
Rolling circumference & speedometer error
Why rolling circumference matters for TÜV and speedometer: tolerance −2 % / +1.5 %, the UN-R39 speedo rule and worked examples for upgrades.
Read more - 03
Wheel sizes: 8.5J × 19 H2 ET45 explained
Rim width, diameter, flange shape and hump explained – plus the ETRTO table showing which rim width fits which tyre.
Read more - 04
Wheel offset (ET) explained
What offset means, how it moves the wheel and how to combine offset, rim width and spacers correctly – with graphic.
Read more - 05
Bolt pattern, center bore & hub rings
How to identify bolt pattern (e.g. 5×112) and center bore, why hub centric rings are needed and which combinations do not fit.
Read more - 06
Wheel spacers: systems, bolt length & TÜV
Choosing wheel spacers: through-bolt vs. bolt-on systems, required bolt length, thread engagement, ABE and registration in Germany.
Read more - 07
Wheel bolts: conical, ball seat & torque
Which wheel bolts fit which wheel: 60° conical, ball and flat seats, thread, length, thread engagement and correct tightening torque.
Read more - 08
Load index & speed rating (tables)
Complete tables for load index (LI 60–126) and speed rating (J–Y). What German TÜV requires and the winter tyre exception.
Read more - 09
Clearance, wheel cover & track width
How much room does the wheel need? Wheel cover under EU 1009/2010 (30°/50°), strut clearance, track widening and how to measure correctly.
Read more - 10
TÜV registration of wheels & tyres: limits and process
ABE, part certificate, ECE approval or individual approval? Which limits apply in Germany, what the inspector checks and how registration works.
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