Planning a new wheel setup? This ET (offset) wheels calculator helps you compare your current fitment to a proposed setup in seconds. Enter old and new wheel width/offset values, add any spacer, and the tool will show how much the wheel moves inward (suspension side) and outward (fender side).
Wheel ET / Offset Comparison Calculator
Compare two wheel setups and see clearance + poke changes (per side).
What does ET mean on wheels?
ET is short for Einpresstiefe (German for insertion depth), and it represents wheel offset in millimeters. Offset tells you where the wheel mounting pad sits relative to the wheel centerline.
- Higher positive ET usually tucks the wheel inward toward the suspension.
- Lower ET pushes the wheel outward toward the fender.
- Spacers effectively lower ET by moving the wheel outward.
Why this calculator matters
Even small fitment changes can cause rubbing, reduced inner clearance, or an overly aggressive poke. A safe setup usually balances three things: suspension clearance, fender clearance, and handling stability.
This ET wheel calculator quickly estimates position changes so you can shortlist fitments before buying wheels or spacers.
How to read your results
1) Inner clearance change
This value compares how close the new wheel barrel will be to struts, control arms, and brake hardware. If the calculator reports less inner clearance, inspect your available space carefully.
2) Outer position (poke) change
This shows how much farther out the wheel sits toward the fender. More poke can look great, but too much often causes rubbing over bumps or when steering.
3) Track width change
Offset changes can widen or narrow track width. Moderate increases are common, but large changes can affect steering feel, scrub radius, and long-term component wear.
Best practices before ordering wheels
- Measure current inner and outer clearance on the car with the wheel mounted.
- Account for tire width and tire model shape (some run wider than labeled).
- Confirm brake caliper clearance (spoke design matters as much as wheel width).
- Consider suspension travel, camber settings, and alignment targets.
- For lowered cars, test-fit whenever possible before final purchase.
Quick ET example
Suppose your current setup is 18x8 ET35 and you want 18x9 ET20. The new wheel is both wider and lower in offset, so it generally moves inward a little and outward a lot. That can reduce inner margin while dramatically increasing fender-side poke.
Use the calculator above to test this (or your own) setup and instantly see exact millimeter differences.
FAQ
Can I run negative ET on a street car?
Sometimes, but it depends on platform, suspension geometry, and legal tire coverage rules. Negative ET often requires wide-body modifications or heavy camber.
Do spacers and lower ET do the same thing?
Functionally for wheel position, yes. A spacer reduces effective ET by the spacer thickness. Example: ET35 with a 10 mm spacer behaves like ET25.
Is this enough to guarantee no rubbing?
No calculator can guarantee clearance in every dynamic condition. Treat results as a planning aid, then verify with real measurements.