I am currently running 245x35 fronts and 285x30 rear tires on 18 in Cup 2 replicas with front offset 52 mm and rear 47 mm.
I am looking at some Porsche BBS 5 spoke 997 wheels that are 8 in front and 10 in rear with offset of 57 mm front and 58 mm rear.
Do you think I will have any clearance problems with the 997 wheels with the increased 5 mm offset in front and 11 mm in back?
Also, when looking at Enkei race NT01 18 in wheels, the offsets for the 8.5 in front are 50 mm and the 10 in rear 61 mm
Is there an ideal offset?
Would you ever use a 5 or 6 mm spacer on the front 997 BBS wheel to get the front offset back to 50-51 mm
Thanks
Dave
i have 52mm in the rear on my 18x10 and the only reason i clear is the camber i have - any less and they would hit - if i had it to do over again i would have gone with about 55
Flash, hit where? brake calipers or to the inside?
the quarterpanels
the smaller the number the farther outward it goes
I use 10 x 18 ET 40 (285 Mich cups) at the rear and 11 x 18 ET 45 (295s) . Both works, tried and tested bumping around quite a bit at the track at occasions when I missed that blacks stuff you are supposed to drive on.... The car is rather low but has 1000 lb springs at the rear. The clearance between the tyre and the "horn" on what I assume is called the quarter panel (the panel between thine rubber join?) is something like an inch or even less. One side the fender has had a bit of "massaging" done to make the inner flange on the fender more vertical providing 5 mm or so extra space (1/5")
At the rear the 11" wheels seems to have 15 mm or so space on the inside which is also the impression forward with max steering angles (the tyres will rub against the inner fenders).
If you have softer suspension and less camber the number ET 52 as per Flash post above makes sense given what I see on the car. Since the ET 45 11" wheels has plenty of space on the inside an ET 58 10" wheel will have even more cleareance (by 9 mm if my Sunday math is correct).
Forward is 10 x 18 ET 47 with 265s. The impression is that this is a max number for outside clearance with 3,5 degrees of camber. Your intentended 8" forward wheels might even need a spacer if you wish a "wide look".
//TL
I have 8.5 x 18 ET 47 wearing 225 40 front and 10 x 18 ET 62 wearing 265 35 rear with no performance alignment (meaning at present I have almost NO negative camber) and there's no possibility of tire rub on my car
I run 285/35R18 rear tyres with 21mm spacers off a GT3 (996 version) and they just touch the rear guards under compression (with negative camber dialed in). I run 235/40R18 fronts and like Flash, these will just touch the plastic inner guards on full lock. I keep looking at 18mm spacers to fix the problem but they are bloddy expensive (as were the 21mm spacers). A wider track seems to make a large difference in corner speeds and lateral G loading. From memory, the datalogger has recorded around 1.35 lateral G.
The actual tyre can make a huge difference as they all vary in size, etc. Road tyres are not a problem, but the Dunlop Dizerra track tyres I use, have a more pronounced lip where the tread meets the sidewall, which cuases the issue. I used to run 295 Pirelli track tyres - no problem, so tyres are all not equal.
Some photo's
Another photo