bmwtye

Wanted to see if anyone could help me with what the offsets of these wheels are. Considering them for my track wheels.

BBS E88

These are 18 inch and are race wheels which do not have offset markings.

The front wheels have a 7 inch back spacing and the rears have a 8.5 inch back spacing

They will accommodate virtually any size brake caliper

Front's are 10 inch wide and rears are 12 inch wide. The car was a 997.1 version (narrow body)

They can be mounted center lock or 5 bolt

The wheel centers are: 522 0288170

bmwtye

From online calculators, Im getting

Front: 38.10
Rear: 50.8

However, I have also found this:
In 2010 the Grand Am Porsches ran 0288170 centers all around (up to 2014) with 2.0 / 8.0 front for ET +31 and 2.5 rear for ET +43.5. In 2012 they went to a 2.5 outer on the front and a 3.0 outer on the rear. Some teams ran other rear combos like 3.5 / 9.0 but the 3.0 / 9.5 was most popular. This just widened to the outside all the way around for offsets of +24.5 front and +37 rear.

So thats why Im confused as the front ET of +31 is a lot different then the calculated ET38 , rears are also different by 7mm too

gt2-josh

Tye,

There is a set of Grand Am spec 10, 12x18 BBS on eBay that came off a 997.1 NB. The seller is asking $3250 and he says he will build them to any spec you want. They look nice. I don't know the seller but I thought I'd pass it along. JBO

bmwtye

That’s why I’m asking here because he doesn’t know offsets and is saying should fit as they ran same cup fenders and flares as I have. But I also know if the front offset is 31 that will not work unless I want to move the radiator brackets forward. Also a 50 offset for the rears is a bit much on a narrowbody

gt2-josh

Got it. I didn't know the dude on ebay is the same guy selling the set on the board. I thought the eBay seller may be able to build them to your spec. Josh

bmwtye

He’s different then the guy selling the set off the 996 on this board. The ebay guy can only swap to 9 and 11. He can’t swap to 9.5 front. A 10” wide offset 38 will fit, so that’s why I’m trying to verify what the real offset is with 7” backspacing.

gt2-josh

Now I got it. Either way it's a good deal especially for getting an ideal setup to fit your Cup fenders. I just bought an ex Mooty set in perfect condition and paid a premium for the Mooty provenance LOL!!! JBO

powdrhound

Post up the width of the inner and outer barrels and I can tell you exactly what offset they are based on 170 centers.

911racer

Have him give you the part number for the centers (should be a 0288... number) and the wheel half sizes and we can calculate that for you.

Thanks

Ed

bmwtye

Thank you. I have requested the wheel half sizes twice now but haven't got a response yet. The wheels centers are all 522 0288170

bmwtye

Ok, heres the info:

2"outer and 8" inner front

2.5" outer and 9.5 inner rear

powdrhound

Tye,
With 170 centers,
Fronts with 2/8 are ET 30.8
Rears with 2.5/9.5 are ET 43.5

Bullet-Racing

I will do the best I can to help here.

As I listed in the ad the wheels are 10" wide with 7" back space front
and 12' wide with 8.5 inch back space rear.

The wheel halves are 2" outer and 8" inner front
and 2.5" outer and 9.5" inner rears

Here is where some of the confusion may be arising from.

The actual measurements on the 10 inch rims when measured from outside to outside on the rim is 11" given that the tire bead is a 1/2" in on both sides they are 10's ...same ratios on the rear

I only have ever had race wheels built by BBS (and Forgeline) and honestly have never dealt with ET measurements

I'm sure there is someone more experienced than me that may be able to calculate the ET

thekid96

Reasonably sure you're gonna have to move your radiator brackets regardless of offset if you run 275's

Antonov

Bumping this thread as I'm interested in 0288170 centers. Does anyone happen to have the following spreadsheet as pictured below only for 0288170 centers that they would be willing to share? A jpeg will suffice as well.

Thanks in advance.