treadsheet

Will the new wheels fit?

Enter the width and offset of both wheels to see how far the new one moves in or out.

My wheel now

Both are stamped on the back of the wheel, e.g. 18x8 ET45.

The wheel I'm looking at

Both are stamped on the back of the wheel, e.g. 18x8 ET45.

Very likely sticks out past the fender

Outside edge sticks out 63 mm (2.48″) further toward the fender.

Inside edge moves 25 mm (0.98″) away from the suspension, so there's more room.

suspensionfenderhub faceinsideoutside
5.98″
Backspacing now
5.00″
Backspacing new
−25 mm
Inside change
+63 mm
Outside change

Rules of thumb. Real clearance depends on your suspension, brakes and tires.

What offset means

Offset is how far the wheel's mounting face sits from its centre line, in millimetres. It's stamped on the wheel as ET (ET45 means +45 mm). Most modern cars use positive offset, which tucks the wheel in under the fender. Zero or negative offset pushes it out, the look you see on lifted trucks.

Reading the result

  • Inside edge: closer to the suspension means less room for brakes, struts and control arms. A few millimetres is usually fine; more needs checking.
  • Outside edge: further out means the wheel and tire stick out toward or past the fender, which can rub when the suspension compresses or you turn.
  • Backspacing is the distance from the mounting face to the inside edge, in inches. Some wheel shops list this instead of offset.