Texas_Sam

I recently purchased some OZ Racing Alleggerita HTL wheels for Base 987.1. Fronts are 8.5 X 18" with Yokohama Advan ADO8 235/40. Rears are 10 X 18 with 265/40. Any advice on size of spacers required? I think 25 to 30mm may work. I think the offset on the fronts is 53mm (ET 53 stamped on the inner rim) and 65mm on the rears. Any advice on type and manufacturer / suppliers for recommended spacers appreciated.

Johnny Danger

What are the specs of the factory wheels i.e. sizes and offsets?

GentlemanRacer

OZ alleggerita for 987.1 would be 53 front and 40 rear. So what you are saying is that you have wheels that have a ET 65 rear. So your fronts will be fine, but minimum rear spacer to clear the struts will be 14 or 15 mm.

RSS, Maxspeed, Eibach, H&R etc

Good luck

GVA-SFO

Had a case (with 996 C4S Turbo Twist, solid spoke), that has an offset of ET65, and to fit them on a Boxster (I did), I had the need to put 25mm spacers.
Basically, the offset number is in mm, and to change the offset from 65 to 40, you need a 25mm spacer.
Also, take in consideration the width “change the result".
I.e.: the offset is the difference between the center of the width, so, if you have an 11 wide, a (theory) “0” offset rim would have the center (fixation plate) or : the rim, will be 5.5 inside in the strut direction, and 5.5 to the exterior, (fender).

So, for example, I can add that on a 986 Boxster, a 996 Turbo Twist Hollow (i.e.: from a 996 Turbo) do not fit in the rear, as the these are 11 wide, not 10, like the C4S Turbo Twist solid spokes !
Or, ..you would need 38mm (!!!!) spacers to clear the shock strut, and then, it would hit the fender ! (Spacers requires longer bolts)

Another interesting info : I upgraded the front brakes (of my 986) to Brembo big brakes with 6 piston calipers, and then, ..my setup with the 18" 996 Turbo Twist Hollow (ET50) wheel (road tires set, with front from a 996 Turbo), ..do not fit as the inside diameter to clear the caliper ..do not make it anymore, this while my OZ Alleggerita 18" (track tires set) they do fit OK.
Measuring both, I found out that the inside clearing dimension is smaller on the OEM 996 Turbo wheels, ..than the one of the O.Z. !

GVA-SFO

Could be different on "all" rims.
On Porsche rims, normally diameter and Offset written on each side of the air valve, exterior.
On O.Z., diameter is on the exterior of the rim, while the offset info ..is in the interior.

GVA-SFO

Back on rims, offset can be OK to clear the inside struts, but think that :

!, 1 : The strut dimensions can be different, i.e.: I have PSS9 (Coil over) on each corners.
!, 2 : I have also "found" that the tire dimensions do play a role, i.e.: 225 wide tires compared to 235 wide tires will play a role in the spacer dimension, as the 235 are 10 mm wider, ..or, 5mm outside, and 5mm inside. OR, this could request 5 more millimeters on the spacers !!!
..As, to clear the struts, the tire (not the rim) is the "component" that is the closest to the strut.

GVA-SFO

After the above "comments", I would say that you should be fine with 25mm spacers (and longer bolts) in the rear, with 10 wide rims that have 65 offset and 265 tires on them.
My rear tires where 285 (on 10 rim), and the offset was also 65.
The 20mm difference (10 goes inside, and 10 outside, as the tire is center mounted !) on the tires, was the reason why I had to be go for more than 25 spacers (!!!)

Visual :
With the 996 Turbo Twist rear, solid spoke from a 996 C4S, road config



With the O.Z. Alleggerita, track config

GVA-SFO

After all this, my last "2" cents comment :
If you will use your O.Z. on the open roads, I would have no "fears" at all about long bolts and large spacers, as on 65mph and/or open road cornering situations, with "non R compound" tires, the sollicitations should be quite "low".
But, if you plan to track these, i.e.: with "R" compound tires, I would strongly recommend to sell the rear O.Z. and get the ones with the "native" right offset, mostly to NOT have long bolts (and spacers) on a track configuration.
I would not like at all to have 25mm spacers and long bolts and go for over 1g lateral on curves, as, the forces on these 25mm "levers" under such conditions should be quite high !