I've been looking for new wheels for my Ghibli for ages now. Don't get me wrong, it's not that I dislike the OEM wheels (I've got the OZ racing 7 spoke 16" wheels, see previous postings for pictures), it's just that there's so little ground clearance on ym Ghibli.
Having said that, I do think the Ghibli looks good with larger diameter wheels and the decrease in the effective offset from the wider later wheels fills up the wheel arches much nicer. But my biggest problem with the Ghibli is getting over speed bumps and living in the Netherlands this is a common problem. It really breaks my heart everytime I hear the catalysts scraping on the ground; this car was obviously not designed with catalysts in mind and they must have been fitted as an after thought, driven by regulation.
It's not just the catalysts though. Not only are there lots of speed bumps in the Netherlands, but lots of brick roads. Couple this with subsidence and there's lots of potential for catching the anti-roll bar and engine sump on the uneven brick road services. So my driver for fitting larger wheels (other than for aesthetics) is to increase ground clearance (although there is another way, by inserting some spacers in the strut towers... ask Enrico for details).
But here's where the problems start. Maserati use really weird wheel fitting specifications, particularly on the early Ghiblis. Mine has a PCD of 5x106mm. I've not seen any other car with this PCD. I'm informed that the center bore is 58.5mm and the offset is ET35. I've looked long and hard for off the shelf wheels with these specifications, but to no avail. The only real option for a perfect fitting wheel is to get them made.
Here's a schematic I've put together of what I think the OEM wheel specifications are versus what I think I'd like. I'm not 100% confident with the proposed offset, but I've not got around to measuring it up properly yet.
One place that does sell customised wheels off the shelf (they appear to make blanks, which they drill out the the PCD and center bore to order and fit hub spacers to attain the correct offset) is Compomotive wheels in the UK. This company supplies wheels to the motorsport industry, noteably for rallycross.
Their MO wheel comes in 18" diameter and both 8" and 9" widths, which would be perfect for the front and rear wheels repectively on the Ghibli. It's probably not a wheel I would choose normally, but given that there's not much alternative (other than having a custom wheel manufactured and paying the price!) I could live with the design; it looks a bit retro and fits the 80s styling of the Ghibli. If you're interested in these wheels, try contacting Mark at Compomotive wheels.
Another alternative is to acquire a wheel with a PCD of 5x108mm and use some wobbly bolts to attach the wheel to the Ghibli's hub. This PCD is more common, particularly with wheels for Volvos. However, the offset of these wheels tends to be a little bit too much and a wheel spacer will be required to get the wheel nice and flush with the Ghibli's body. However, when using wobbly bolts, it's not recommended to have a wheel spacer thicker than 5mm, unless it's hub-centric. Try getting a hub-centric wheel spacer with these specifications. If you go this route, then try talking to William at Performance Alloys in the UK.
I'm still in two minds as to whether or not to purchase these wheels, since I'm also toying around with getting a new exhaust, which should help remedy the ground clearance problem with the catalysts and give me some more power to boot.
I'll keep you posted.