Have a great opportunity to pick up a set of new 993 wheels
at a great price, backs are correct 17" x 9" (55mm) offset,
but fronts are of the 7" 55mm offset variety instead of the factory 7.5" 65mm offset. Will the 225/45 17" tire fit correctly? Could I use the wheel as is, or would I need a 10mm spacer to get everything to line up? Thanks.....
I have 17x8 55 on my front. There is no problem, except on the odd occasion when I reverse, on full lock. Still don't know why this only happens when I reverse. . . . Some folks seem to use the 993 and/or Boxster wheels, others say that it can't be done. It can - but it's not optimum. Adding spacers sadly will not have the effect you desire - you want to bring the wheels 'in' 10mm, rather than take them out a further 10. If you think about this, you'll realize what I mean - the offset being the distance measured from the centre of the wheel to the face where the wheel bolts to the hub. I'm sure you must have read of the now infamous 'negative' spacers - they seem to belong to the same school as 6sp 928s - one of the many long standing 928 jokes.
Hope that helps.
I'm running the 17 X 7, 55mm offsets on the front of an 89 S4, mounted with 225/45 17s, and have experienced no problems with normal highway driving. I have no high speed experience with this combo, so I can't comment on that.
As you have read, it has been done. However, as also mentioned, it's not the optimum arrangement.
Over time, 928s got heavier, particularly up front. In order to compensate for the increased load on the front tires, the wheels were made a bit wider, which reduced the tire deflection at the rim. Moreover, the front wheel offset crept up to 63 or so to accommodate the larger calipers while keeping the tire from going too far outboard.
If you want a really good fit, then 928 OEM wheels are the best, but usually are the most costly. Also, there are 8"x17" 993 Cup wheels with a 70mm offset that work very well, and one can put a 235/45 or even a 245/40 on it, and still be ok. Again, it's an OEM Porsche wheel, so expect to pay more for it than an aftermarket wheel. Lastly, there are now plenty of aftermarket wheels that will fit the 928. Any of the 'Big Three' can get them for you at a reasonable price. YMMV.
~ Merry motoring ~
a 7"55mm offset puts the outside edge of the wheel 2mm further toward the centre of the car than an 8" 60mm offset - standard fitment on a CS, SE or GT, and the inner edge 10mm further away from the centre. So it will fit fine and shouldn't hit anything. The only issue is that the centre of the wheel has moved out by 5mm and will impart s lightly grater load on the front wheel bearings and in theory would need slightly different alignment settings. I suspect 5mm is not that critical but those in the know can put me right.
No difference on alignment settings and Porsche has put much bigger loads on those wheel bearings. The rears on the GTS on the sealed bearing are even a worse scenario. Many have raced on big offsets with large wheel/tire combos under flares. None have ever complained about a wheel bearing as a wear part that had to be changed a bunch. Anything within reason is ok. We are still talking about a wheel bearing that is inside the contact patch here. It isn't like putting reversed rims on a cheap truck bearing. The 928 hubs/bearings... especially the front with it's wide spread laterally between individual bearings is about as rugged as you will find. The 911 guys are always having to beef up theirs and the 914 guys too... We are lucky in that respect.