AU wheel offsets - what will fit
As most of the T-Series clan will know I have done my fair share of wheel swaps with the AUs (sedan, wagon and LWB models)
So for people who need to know what to look for in aftermarket rims here's some vital stats for you.
Up front - not a lot of scope here for a couple of reasons. Firstly the physical space available and secondly the need to keep the front and rear rolling circumferences as close as possible. Cars with ABS/TC don't like differences of any more than 3% or they start to get confused.
So ... the most common request is for the absolute widest wheel that will fit inside the arches ... generally a staggered setup with 8.5 front and 9.5 rear for those who want to fill the guards as much as possible and still stay legal (well, almost).
Front offset for an 8.5" rim cannot be more than 32mm - any higher will have the tyre hitting on the upright. 30mm is actually ideal as it keeps the original factory clearance on the inside. Therefore simple math tells us the whole extra half inch of rim width is to the outside, thus filling the guards very nicely. Be warned that unless you have very (I mean VERY) stiff front springs you will have to be extremely careful traversing driveways etc with the wheel turned or contact with the guard is guaranteed. In fact this can also be the case with 8" rims so anyone who has driven on 8s will already have their driveway entry technique sorted.
Now, what tyres for the 8.5" rims? Well here is the rub ... it is in fact difficult to fit a tyre wider than the same which you can put on an 8" rim ie. 245/40-18 (Talking 18s because it is generally the best compromise for performance/comfort and also tyre availability at reasonable cost). You can apply the same theory though for 17s or 19s whichever your preference may be. This isn't so much because of physical space but rather the other problem I mentioned earlier - the need to keep front and rear rolling circumferences within 3% of each other. This will all become clearer when we talk about rear tyre sizes.
Moving to the rear then ... 9.5" rims can be fitted but again the correct offset is absolutely imperitive. It must be 30mm. ONLY 30mm. Even then it may be necessary to remove some of the plastic inner guard cover, and definitely necessary to massage the arches. 9" rims on the rear allow for some degree of latitude with offsets - ranging from 36 to 20 (even 15 with guard massaging).
Rear tyres? - there are two choices which fall within 2% of original specs (245/40) - 275/35 and 285/35. Either will work perfectly on a 9" or 9.5" rim. However on the 9.5" there will be no "belly" at the rim to offer it any protection from pothole edges or gutters. A better choice of tyre on the 9.5" would be a 295/35 or even a 305/35. The problem here however is getting fronts to match - because you have now gone up in rolling circumference you have to do the same at the front; BUT you can't step up to a taller tyre on the front or you contact the upper ball joint.
Which brings us full circle on front rim width; my logic is this ... if you can't fit a wider tyre to the front on the 8.5" rim then you may as well stick with an 8". This gives you some scope with offsets - 36mm to 24mm.
For me a perfect set-up on the AU is 8s/9s with 245/40 and 275/35 tyres. I like 30mm offset front and 24mm offset rear for a nice stance - it also helps equalize the car's track which is wider at the front than rear in stock form.
Hope this helps some of the young'ns looking to modding their AU rides.
Oh, and if you want to know how to fit 9s all round ..... LOL ... take a look at my thread in the build section ... AUs Mistery.
