Hello-

I need someone to help me with fitment / offset questions please. I have a 1977 911 with 930 turbo widebody fenders. I would like to upgrade to 18's and from what I have seen 18x9 & 18x11 have been done. Now the wheels I am looking at are three piece, I want low offset, staggered ofcourse. The wheels I am looking at potentially are 18x9 with 3.5" outers ET in the 20 to 15 range & 18x11 with 5.5 outers ET in the -10 / -5 / -15 range. Could someone please clarify for me the ideal offset, outer / inner lips should be? so that I can order the correct fitment. Here are some pics below of the stance I am looking for. Thanks

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Typically the front wheels used are a 8.0 or 8.5" with a +10>+20et depending on the car...this width is common because the size of the tire used and recommended. Going to a 9.0 may require an increase in tire size that may require additional fender modification, or would cause the recommended tire to be severely rounded on the sidewall shoulder.

For the rear, it is complicated; because the cars age and in that era so many of these cars used factory track spacers, and many cars had additional wide body treatments...you mentioned that you are going to a 3pc wheel set up? I would suggest contacting your wheel manufacturer and have them direct you in doing a full measure up on the car...this way you can accomplish getting the maximum application to your exact vehicle. Camber and tire size also play a major role in the overall appearance. Make sure you check and inform the wheel manufacturer if your car is still running the factory track spacers? Also if the wide body is different from the factory. Typically the std Turbo would use a 10.0, 10.5, or 11.0 depending on the wheel, and the offset was anything from -5>+20 depending if the car remained with the factory spacers or had them removed...again it would be best to do a full measure up on your exact car.

To get the desired wheel offset, you may want to do a string and weight drop from the top of the fender so you can measure the distance from the inside out, this way you can calculate how you want to position the offset.

I hope this info helps

Jim

 

That is a ton of info! thank you so much for responding. I have some measuring to do thanks.

 

My pleasure, I hope it works out for you.

Be sure to post pics when the car is done...I remember back in 1982 my sister dating some guy with a 930 turbo, the car looked similar to the photo you posted...black with Gold center BBS wheels...I remember going for a ride and it was just awesome! Great car, good luck, again I hope the info provided is useful.

Jim

 

What wheels do you currently have on the car? Use their width and offset as a guide to your desired look.
If you understand what offset really is, it is easy to figure.
If you can tell me what are the sizes and widths of your current wheels and what you want to achieve, I can help. PM me

 

I am currently running 17x7.5 ET 23 (205/50) & 17x9 ET 15 (255/40) I am running the stock 1" spacer for the rears and the wheels are still too tucked in. I would like to get 285's in the rear and 235 or 245 up front. I believe it is 13" from the inner wheel well to the outer fender for the rear and 9" up front. Here is a pic:

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First, do you understand offset and how it works?
The ET on the wheels is the offset in mm and 25.4mm = 1 inch
Imaging your rim being 2 pieces, the barrel and the center
"0" offset is when the mounting point of the center to the hub is dead center of the rim. (+) offset happens if you slide the barrel inward giving rim less lip. (-) offset happens when you slide the barrel outward giving the deeper dish look.

<-- --> ----I---- ---I----- -----I---
in outside 0 offset - offset + offset

If you simply added width to the barrel but left offset the same, you would gain 1/2" inside and outside for every added inch. Going to a 11" rim would get you 1" in each direction. If you lowered the offset to 12mm the barrel would push out another 1/2" toward the fender. and leave you with 1/2" less clearance on the inside than you currently have. Tape a plumb line off the fender and measure the amount of distance you could push the rim outward. Also make sure there would be nothing hitting on the inside if you added 1/2" in there.

Hard to tell the fronts from the pic but if you added 1" to width with the same offset(8.5"rim), you would be adding 1/2" to the barrel inside and outside. Put one of your 1" spacers on the front and see if that would work. If it does, you could drop the offset by another 1/2" or 12.7mm and push that barrel outward more. The offset would be @10mm.

If you jack up the car, make sure it settles before taking measurements or you can screw things up.