The export/UK version of the Impreza up until the 1998 version came with 15in alloys. The MY98 and Japanese spec. cars have 16in alloys which undoubtably improve the looks of the car but also improve the handling.

The larger alloy reduces the depth of the tyre sidewall (to keep the overall rolling radius constant), and thus improves stability. The largest recommended alloy size for the Impreza is 17in although it has been known for larger 18in items to be fitted with some modifications to the wheel arches.

Speedline Supertorismo 17" 6 spoke alloys (not suitable for MY99 and 4 pot caliper STi)

It has only been recently that the correct fitment has become generally available for the Impreza. The 5 stud fitting and also a rather strange standard offset of 55mm (anything from 45 to 55mm is probably OK) has meant scarcity in supply. Another attribute to be concidered is the clearance between any wheel "spoke" and the brake calipers which on the latest MY99 are much larger.

MIM 17" multi-spoke alloys from Scoobysport

As mentioned above fitting a larger wheel improves stability and this can be shpwn by back to back tests of what I term the "door slam test". On the 15in alloys slamming the drivers door quite hard had the car rocking back and forth about three times. Do the same test on the 17in and the car just rocks once if that. Now imagine going into a left, right, left series of bends and you can imagine the sidewalls flexing similarly degrading handling.

MIM 17" multi-spoke alloys

The main disadvantages of a larger alloy are increased road noise and decreased comfort because there is less rubber between the road and wheel. The other thing to mention is that a 17in alloy with tyre weighs more than the equivalent 15in or 16in item (density of alluminium alloy is greater than rubber). Thus the unsprung weight is greater and by rights an increase in damper settings should be made to compensate but for a compromise the advantages in stability outweigh this effect.

Speedline Supertorismo 2 17" multi-spoke alloys from Prodrive

From left to right, Stilauto SR500, Mille miglia Evo, BK Racing 299. Many thanks to Mark R and Duncan W for naming them for me. The last (very similar to the Wheelmania Vortex) must be a real pain to clean! See below for a closer look.

The OZ alloy similar to the P1 multispoke is available with more spokes from third party outlets. Seen here with AP 4 pot brakes.

New Age (MY2001-)

The New Age Impreza has the ability to take larger alloys without the clearance problems seen on the classic (pre MY2001) and here we see an STi fitted with 225x19in OZ alloys available from Scooby Mania.
These wheels will even fit over the massive Brembo/STi calipers.

Team Dynamics Racing 7.5x18 Vector available from TSL.

Tecnomagnesio Detroit F1 available from Scoobysport.