ERA 289FIA WHEEL SIZES AND OFFSETS

Over the years, we've put many different size wheels on our FIAs.  The table below shows what we have determined to fit correctly with the tire size indicated.  I can supply supply the wheel manufacturer with more pin-drive and bolt-on wheel hub dimensions on request.  

For machining reference, basic drawings of the front and rear Pin-drive hubs are here.

Special notes, Drawing links, and Hints

Generally, you can calculated the offset by using 0.4" for the width of the rim beads. So offset = (width-0.8')/2 - backspacing.  (That defines the offset as negative if the wheel moves toward the car centerline.)

Note!  You must maintain at least 0.8" clearance for the optional 4-piston front calipers.  See the picture below.

 If you need help with this, please e-mail us* with the intended diameter, width and tire sizes.  

FRONT

(Outside surface to the right)

PDF Drawing for printing

If the back side of the wheel is machined, make sure that the drive pin hole depth is maintained.

SAFETY WIRING

We strongly recommend that you safety wire the wing nuts.  We like to keep the finished wire snug.  Some leave a little slack so that if the wing nut moves, the wire slack will show a difference.  More safety wiring hints here.
Procedure: Drill a 1/8" hole in the wingnut. See below for location.  Some like to drill a hole in each of the wings to make it easier to get an ideal angle-pull.
Loop a length of wire around a wheel spoke. Make it longer than you think you need. You can trim the extra length later.  Wire so that the wing nut is being tightened!  The right hand threaded wing nut is on the left (driver's) side.  The passenger's side wing nuts are left hand thread. In other words, tighten the wing nuts in the opposite direction of forward wheel rotation.
Clamp the pair of wires with the pliers where you expect to end the first twist section. Don't get too generous initially - you can add more length if necessary.   Slide the central sleeve down on the pliers to retain the "clamp". Pull the knob at the end of the pliers.  Twist the wires to within 1/4" of the wing nut connection, no more than 6-8 turns per inch.  Twist with no more
Loop one leg of the wire through the hole in the wing nut and clamp the pair of wires as before.  Twist about an inch of wire.
Clip the excess wire from the twist and bend out of the way.