I was just looking at the wheels on our 528i Touring and had a question about the markings. This is my first post so please go easy on me if this is an obvious question; however, I searched the web and couldn't find an answer so thought I'd ask here.
The car has staggered 2008 Style 124 18" wheels, 18" x 8" on the front and 18" x 9" on the back. These are OEM wheels (E60) made by BBS and look amazing on the car (which has an M5 front and can be seen in my profile's photo album). And since someone will probably ask, the tires are 18” Dunlop Direzza DZ101 Digi-tyre 245/40R18 93W High Performance Summer Tires. We had the car up on a lift today and I was looking at the wheel markings on the back side of the rims when I noticed something odd. The markings on the front and back wheels are as follows:
Front - 8Jx18EH2 IS 20
Rear - 9Jx18EH2+ IS 32
So reading these, we know that the front wheels are 18" x 8" with a "J" bead profile, an "Extended Hump" hump profile and a 20mm positive offset. And, the rear wheels are 18" x 9" with a "J" bead profile, an "Extended Hump 2+" hump profile and a 32mm positive offset.
Here's my question: Ordinarily, I would expect to see the offset markings to be indicated with the letters ET prior to the offset number (i.e. 8Jx18EH2 ET 20 and 9Jx18EH2+ ET 32) but in this case both wheels are marked with the letters IS. Does anyone know why and what the IS stands for? I know the ET comes from the German word "Einpresstiefe" which means "offset". Since positive offset = inset, the only thing I can come up with is that IS stands for the English word "inset". Is this correct?
I know I am nerding out big time with this question, but it is bugging the heck out of me! Thanks in advance for you help and patience!
I would also like to know the exact same. Are ET and IS universally the same meaning ie offset in mm?
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