997_rich

I have a narrow body 997 and I'm thinking about custom wheels.

Right now I run:

18x10 offset 58 with 17mm spacer
18x8 offset 57 with 7mm spacer

and I love the way they look from the outside so I'd like to have the new wheels matching the amount they stick out of the wheel well. So that means if i could buy wheels that same size with the spacer built in they'd be:

18x10 offset 41mm
18x8 offset 50mm

Right? Am I doing the math right there? You subtract the spacer when the wheel mount face is outboard of the centerline of the wheel.

Now, I want to get wider wheels that are each one inch wider than what I run now. So I'm looking for:

18x11 offset 28.3mm (=41-12.7)
18x9 offset 37.3mm (=50-12.7)

there's a half inch more wheel width now so I have to subtract that from the offset if i want the wheels to stick out of the wells the same amount as today? is that right? or do I add the half inch??

Thanks in advance.

997_rich

also interested to know opinions on a 9" or 8.5" width in the front when paired with an 11" rear. This would be for spring/summer/fall road use and a few track days per year. My old wheels would become winter dedicated wheels.

Turn3 Autosport

You have it close You were doing great up till the time you added some extra width to the wheel....

The spacer math is correct, your current wheels plus spacers give a net offset of 41mm rear and 50mm front.

I get that you want to leave the outer lip positioned where it is now once width is added to the wheels, meaning it all goes on the inside of the wheel. The "Frontspace" of the wheel will remain the same and the "Backspace will increase by the added width. Offset will then change (greater) by half the added width as the centerline of the wheel will move inward from it's current location reference the hub by this same amount.....

So according to your calculations your front 9.0 wheels would be et62ish and the rears 11.0 inch wheels would be et54ish...

That said, we would build a 9.0 et51 or and 8.5 et44 or 51 for the front and the rear 11.0 et57-63(ish). The as measured 54 offset on the 11.0 would be very flush....

Something seems odd with your front wheels, can you post a pic of the current setup? Is the offset stamped on the wheels or did you measure it? That said we have run 15mm spacers on factory wheels up front with out any issues....


Cheers

997_rich

Thanks Jeff! so I should've added that 1/2":

rears:
18x11 offset 53.7mm (=41+12.7)
fronts:
18x9 offset 62.7mm (=50+12.7)

I'm reading the offset right off the wheels. they're the stock 18" 5 spokers that go on the C2. I've got 7mm spacers on them... I could have lived with 5mm spacers but I tried 7mm on a lark. 2-3mm either way probably won't make much of a difference.

Fikse Wheels

Jeff,
Happy to see you here on Rennlist.

Rich,
Jeff is right on with the recommendation of wheel widths and offsets. I would use 18x9 51mm and 18x11 57mm rear.

jhbrennan

I find this tool useful -
http://1010tires.com/WheelOffsetCalculator.asp

Turn3 Autosport

Pleasure to help with the math

Let me know if we can help you in your search for a quality set of wheels!

Cheers

gabfab

Hi, I have also been struggling with an offset question/calculation and your posting motivated me to do the same. I have a 997.2 NB and have access locally to a dedicated set of winter wheels mounted with Michelin PA tires. They were used for a season on a 997 WB and therefore the rears have an ET of 40mm. 58/60 mm is the recommended offset for NB. Will it be OK to use them? Any concerns? Thanks in advance,

gota911

Those wheels ^ will be flush with the rear fender, or maybe extend a little beyond the fender.

997_rich

Does anyone know why the math for the front wheel offset doesn't seem to be inline with the suggestions from Jeff and Alan?