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JDM Toolkit

Free calculators for wheel fitment, tyre sizing, SA import costs and more — no login required.

Wheel Offset Types

Understanding how hub mounting position affects wheel stance.

CL HUB FACE BS NEGATIVE Hub near back · aggressive stance BACK FRONT HUB=CL ZERO Hub at centre · neutral BACK FRONT CL HUB FACE BS (longer) POSITIVE Hub near front · tucked in BACK FRONT
1Lay the wheel face-down on a flat surface.
2Place a straight-edge (ruler or level) across the back flanges.
3Measure from the straight-edge to the hub mounting face — this is your Backspacing.
4Measure the total Overall Width (outside of back flange → outside of front flange).

Calculate Offset (ET)

Enter backspacing and overall width to get ET offset.

in
in

Offset Result

ET (metric)
–
Offset (imperial)
–
–

Calculate Backspacing

Know the ET? Work backwards to find backspacing.

mm
in

Backspacing Result

Backspacing (in)
–
Backspacing (mm)
–
Tyre Calculators

Tyre Size Decoder

Enter your tyre size (e.g. 225/45R17) to get real dimensions.

mm
%
in

Tyre Dimensions

Sidewall Height
–
–
Overall Diameter
–
–
Rolling Circumference
–
–
Width (inches)
–

Speedometer Error

Changed tyre sizes? Find out how far off your speedo reads.

Stock Tyre
mm
%
in
New Tyre
mm
%
in

Speedometer Error

Stock Diameter
–
New Diameter
–
–

Indicated (km/h)Actual (km/h)Difference

Spacer → Effective Offset

Adding spacers? See your new effective ET and track change.

mm
mm

Effective Offset After Spacer

New ET (mm)
–
New ET (in)
–
Wheel Moves Out
–
Track Increase (both)
–

Rim ↔ Tyre Width Compatibility

What tyre widths will fit your rim?

in

Tyre Compatibility

Minimum
–
mm
Maximum
–
mm
Recommended: – mm to – mm
––
MinRecommendedMax

Disclaimer: These are estimates based on common SARS tariff headings. Actual duties depend on the specific HS code, origin country, and SARS valuation. Always confirm with a licensed clearing agent before importing.

SA Import Duty + VAT

Estimate your total landed cost importing JDM parts into South Africa.

ZAR
ZAR
ZAR

Note: Estimates based on typical SA courier rates (Courier Guy / Fastway / Dawn Wing). Actual quotes may vary. Wheels and heavy freight may incur surcharges — always get a confirmed quote for large shipments.

Domestic SA Shipping Estimator

Estimate door-to-door courier costs within South Africa.

kg
ZAR
Dimensions (for volumetric weight)
cm
cm
cm

Power

Enter any one value — the rest update instantly.

kW
hp
PS
1 kW = 1.341 hp (SAE) = 1.360 PS (metric)

Torque

Nm
lb-ft
1 Nm = 0.7376 lb-ft

Boost Pressure

bar
psi
kPa
1 bar = 14.504 psi = 100 kPa  ·  Gauge (above atmospheric)

Weight / Mass

kg
lbs
1 kg = 2.2046 lbs

PCD / Bolt Pattern Checker

Check if a wheel's bolt pattern fits your car, or use the JDM car lookup below to find your specs.

mm
mm
mm
mm

JDM Car Fitment Reference

Bolt pattern, centre bore, stock offset range and stud pitch for popular JDM platforms. Click any row to pre-fill the checker above.

Car Years PCD Centre Bore Stock ET Range Stud Thread

Enter your new wheel specs and your stock reference (the baseline the fender was designed around). The visualiser draws both to scale and shows how far the tyre edge moves relative to the fender lip.

New Wheel Setup

in
mm
Tyre
mm
%
in

Stock / Reference Setup

The fender lip is assumed to sit flush with the outer tyre edge of this setup.

in
mm
Tyre
mm
%
in

Power to Weight

Estimates 0–100 km/h, 0–60 mph, and quarter mile. Results are theoretical — real-world times vary with driver, conditions, and traction.

kW
kg
Done calculating? Go log it.

GarageLog lets you store your wheel specs, offset notes, service history and mods against each car — free, from the same garage.

Open GarageLog ↗