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Discussion Starter · #1 ·
The 718 has been out for nearly a year, yet there is almost no info regarding which aftermarket wheel sizes will work. Tire Rack doesn't even have the 718 in its database yet.

So to start a database, I've compiled all of the wheel options available for the 2018 718 below. All four models have the same choices from 19" upward; the 2.0l Cayman and Boxster have the 18" choices, which likely indicates that they won't work with the 911 Turbo brakes that are on the "S" models:

18" Boxster IV (alloy): 8x18 ET 57 with 235/45 ZR 18 tires (front); 9.5x18 ET 49 with 265/45 ZR 18 tires (rear)
18" Cayman III (alloy): 8x18 ET 57 with 235/45 ZR 18 tires (front); 9.5x18 ET 49 with 265/45 ZR 18 tires (rear)
19" Boxster S IV (flow-formed): 8x19 ET 57 with 235/40 ZR 19 tires (front); 10x19 ET 45 with 265/40 ZR 19 tires (rear)
19" Cayman S IV (flow-formed): 8x19 ET 57 with 235/40 ZR 19 tires (front); 10x19 ET 45 with 265/40 ZR 19 tires (rear)
20" Carrera S IV (alloy): 8x20 ET 57 with 235/35 ZR 20 tires (front); 10x20 ET 45 with 265/35 ZR 20 tires (rear)
20" Carrera Classic II (alloy, two-tone): 8x20 ET 57 with 235/35 ZR 20 tires (front); 10x20 ET 45 with 265/35 ZR 20 tires (rear)
20" 911 Turbo IV (forged, two-tone): 8.5x20 ET 57 with 235/35 ZR 20 tires (front); 10.5x20 ET 47 with 265/35 ZR 20 tires (rear)
20" Carrera Sport (alloy, painted/machined): 8.5x20 ET 57 with 235/35 ZR 20 tires (front); 10.5x20 ET 47 with 265/35 ZR 20 tires (rear)

Some notes:
- All front wheels have an ET57 offset, even though the last two options are .5" wider. This suggests that 8"-wide front wheels can have an ET as low as 51 and as high as 62 without clearance issues.
- Rear wheels vary a full inch in width between 9.5" and 10.5". What's interesting is that the offset goes down 4mm, then back up 2mm, as the wheels get wider. This suggests that there is at least 10mm of leeway (!!!) on either side of the rim with the 18x9.5s fitted. So:
  • 18x9.5 rears can have an ET as low as 39 or as high as 59
  • 19x10 and 20x10 rears can have an ET as low as 39 or as high as 51
  • 20x10.5 rears can have an ET as low as 39 or as high as 55
without clearance issues.

Someone check my math, please, but I'm fairly certain these guidelines are solid.
 

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The previous 981 and 987 wheels, and their aftermarket counterparts should fit. The issue is the larger rear wheel on the 718 vs previous gens
 

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Discussion Starter · #3 · (Edited)
The previous 981 and 987 wheels, and their aftermarket counterparts should fit. The issue is the larger rear wheel on the 718 vs previous gens
Correct -- hence the thread title "aftermarket" instead of "OEM". :D

However, I would be careful regarding aftermarket 987 fitments for two reasons:
- The 1/2" larger rear rim widths
- The change in brake outfitting for the 718:
718 Cayman/Boxster brakes = 987 Cayman/Boxster S brakes
718 Cayman/Boxster S brakes = 991.1 911 Turbo brakes

This is precisely why Porsche OEM 18" rims won't fit the 718 "S" models. That's the big unknown here: those who want to track/AutoX/winter-tire your 718 "S" cars will be hard-pressed to find an off-the-rack aftermarket 18" rim that will work. You'll have to research 991.1 Turbo fitments as a start.
 

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I'm going to stick with the booster s wheels for winters for now. I may get some light oz wheels unless I can find a cheap set of 20" carerra s wheels.
 

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All of the wheels listed in the OP's post are shown in the build your own Porsche web site.

I googled and found this list "Porsche 718 (982) Cayman & Boxster option and build codes" on this web site:
https://www.stuttcars.com/technical/option-codes/718-982/

this list shows build code " 433 20" 991.2 Carrera S wheels"

Note this is different from the OP's Careers S wheel as it clearly designate that it's 991.2 wheel. I looked that wheel up on the build your own Porsche website and it shows this:

Set of alloy wheels with five imposing open-ended spokes.911 Carrera models:Front: 8.5 J x 20 (ET 49) with 245/35 ZR 20 tyres,Rear: 11.5 J x 20 (ET 76) with 305/30 ZR 20 tyres911 Carrera 4 models:Front: 8.5 J x 20 (ET 49) with 245/35 ZR 20 tyres,Rear: 11.5 J x 20 (ET 56) with 305/30 ZR 20 tyres

The fronts are basically the same size but the rears are much larger. I want the largest set of factory size wheels i can get for SCCA Autocross.

So my question is does anyone know if this is correct? I question if an 11.5" wide wheel will actually fit, even with a 76mms offset?
 

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While I can't say for 100% certainty, I doubt 11.5" with a 76mm offset would fit. The 11" rims are a tight fit on the GT4s.

If you plan to run a stock SCCA class, the question is moot due to SCCA rules.

13.4 WHEELS
Any type wheel may be used provided it complies with the following:
A. It is the same width as standard and as installed it does not have an offset more than ±7.00 mm (±0.275”) from a standard wheel for the car. The resultant change in track dimensions is allowed.
 

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Discussion Starter · #7 ·
First off: That list, while large, is incomplete because it doesn't include the 20" 911 Turbo IV option that is clearly on the Porsche NA website as an option for the 718 -- or at least it was when I compiled the list.

Second: Porsche OEM wheels come in different widths for different models. This does not mean that any width will fit any model. Option 433 on the list that you linked to, the 20" Carrera S IV, does look to be the same style as the one used on the 991.2 Carrera S. However, the width available on the 718 is 10"; the width on the actual 991.2 Carrera S is 11.5". This does not mean they are interchangeable between the models. It simply means the same style wheel is used, which is common in Porsche-dom.

Third: Base 911.2 Carreras come with an 11" wheel standard, which is wider than any optional OEM 718 wheel. I seriously doubt you can go much wider than what is OEM on the 718 -- certainly not by a full inch, which equates to 13mm of offset in both directions away from the wheel's centerline.

Beyond my fitment guide, I would consider contacting a wheel manufacturer that has actually fitted 20" wheels to the 718 for more precise feedback on offsets and tolerances.

All of the wheels listed in the OP's post are shown in the build your own Porsche web site.

I googled and found this list "Porsche 718 (982) Cayman & Boxster option and build codes" on this web site:
https://www.stuttcars.com/technical/option-codes/718-982/

this list shows build code " 433 20" 991.2 Carrera S wheels"

Note this is different from the OP's Careers S wheel as it clearly designate that it's 991.2 wheel. I looked that wheel up on the build your own Porsche website and it shows this:

Set of alloy wheels with five imposing open-ended spokes.911 Carrera models:Front: 8.5 J x 20 (ET 49) with 245/35 ZR 20 tyres,Rear: 11.5 J x 20 (ET 76) with 305/30 ZR 20 tyres911 Carrera 4 models:Front: 8.5 J x 20 (ET 49) with 245/35 ZR 20 tyres,Rear: 11.5 J x 20 (ET 56) with 305/30 ZR 20 tyres

The fronts are basically the same size but the rears are much larger. I want the largest set of factory size wheels i can get for SCCA Autocross.

So my question is does anyone know if this is correct? I question if an 11.5" wide wheel will actually fit, even with a 76mms offset?
 
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Thanks for the replies...

The SCCA rule book also states that you can run any wheel size offered by the factory... With the earlier Boxster/ Cayman cars most fo!ks are running XRR wheels... Thoese are 8.5x19 ft & 10x19 rear. With The +/- 1 inch diameter allowance, most drop to 18" di a for better gearing. Note that wheel is not offered on the 718.

My point with the wheels i identified is if this list is correct ( which I can not yet confirm) then the 991.2 wheels are SCCA legal and their availability suggests that Porsche says they will fit. I fully understand these are not 718 wheels, they are 991.2 so 911 wheels, but I'm only reading what the list says.

I'm also very suspect about how an 11.5" wheel will fit.... So the point of my question was has anyone tried anything that wide? I have a set of 12x18 from my GT3, I don't recall the offset but I intend to put them on the car and look for interference.

Thanks!
 

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Discussion Starter · #9 ·
Again:
<<Porsche OEM wheels come in different widths for different models. This does not mean that any width will fit any model.>>

What the SCCA rule means is any wheel that is offered as OEM on that specific model. So you can't take a wheel offered on a 911 and use it on a 718, even if it fits. Or: You can't take a wheel from, say, a Dodge Viper and slap it on an SRT-4.

You're limited to what is offered for the model: style, width, offset, etc.

My point with the wheels i identified is if this list is correct ( which I can not yet confirm) then the 991.2 wheels are SCCA legal and their availability suggests that Porsche says they will fit. I fully understand these are not 718 wheels, they are 991.2 so 911 wheels, but I'm only reading what the list says.

I'm also very suspect about how an 11.5" wheel will fit.... So the point of my question was has anyone tried anything that wide? I have a set of 12x18 from my GT3, I don't recall the offset but I intend to put them on the car and look for interference.

Thanks!
 

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Correct... no question, only OEM wheels for the exact model are legal.

I apologize if I've been unclear... but my point is according to the list I linked, I can go into a Porsche dealership and order a new 718 Cayman S from the factory with 991.2 Carrera S wheels ( 911 Carrera S wheels, not 718 Carrera S wheels) as a factory build option for the 718. That makes those wheels OEM for the 718, and subsequently SCCA legal.

So again, my question is, is this list incorrect? and if it Is, has anyone tried to fit that large of a wheel?

I'm currently away from home but once I return I intend to try my GT3 18" track wheels on my 718 CS. I will post what I learn...
 

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i run a set of 18" volk wheels for the track i got from a friend who ran them on his GT4 once last year. 235 in the front, 265 in the rear. much easier to find 18" track tires, and cheaper too.
 

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Discussion Starter · #12 ·
The 10"-wide version of the Carrera S IV wheel (from the 718 S) is legal on the 718 for SCCA.

The 11.5"-wide version of the Carrera S IV wheel (from the 911 Carrera S) is NOT legal on the 718 for SCCA.

The list is correct. The option is for the 10"-wide Carrera S IV, NOT the 11.5"-wide Carrera S IV.

Correct... no question, only OEM wheels for the exact model are legal.

I apologize if I've been unclear... but my point is according to the list I linked, I can go into a Porsche dealership and order a new 718 Cayman S from the factory with 991.2 Carrera S wheels ( 911 Carrera S wheels, not 718 Carrera S wheels) as a factory build option for the 718. That makes those wheels OEM for the 718, and subsequently SCCA legal.

So again, my question is, is this list incorrect? and if it Is, has anyone tried to fit that large of a wheel?

I'm currently away from home but once I return I intend to try my GT3 18" track wheels on my 718 CS. I will post what I learn...
 

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Ok, thanks for clearing that up for me. So if I understand you correctly, the build list is correct but the wheels identified as 991.2 Carrera S wheels are not really 991.2 wheels, they are in fact a 718 specific versions of the 991.2 Carrera S wheel.

Btw, here's are all of the wheels found in the build/option sheet.

395 18" Boxster 981 wheels
396 18" Cayman 981 wheels
397 19" 982 Boxster S wheels
398. 19" 982 Cayman S wheels
427 20" Carrera Classic wheels
433. 20" 991.2 Carrera S wheels
XRD 20" Carrera Sport wheels

In any event, this makes the turbo or Carrera classic wheel size the largest SCCA legal wheel (8.5x20 & 10.5x20).
 

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I'm toying with the idea of getting some Mickey Thompson ET Street S/S drag radials for the back of my 718 with regular PASM. Let's avoid the whole debate about "a Porsche is not a drag race car".

There seem to be two potentially viable sizes:
P275/45R18 which is 10" wide and 27.8" tall (0.5" taller than the stock 20" Pirelli Tires)
P305/40R18 which is 11.1" wide and 28.0" tall (probably want an 11" rim)

I'm pretty sure the P275/45R18 on a 10" rim will fit without issues since the stock base size is P265/45R18 on a 9.5" rim and 10.5" x 20" rims are an option on the base model.

Has anyone put a P305/40R18 with an 11" rim (or 10.5" rim) on the rear? Any rubbing issues? Thanks!
 

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What’s the consensus with a 245-35-20 front and 285-35-20 rear winter tire set working on the Carrera S wheels? Seems like it’s not too far off from OEM with some extra sidewall and overall ground clearance.
 

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What’s the consensus with a 245-35-20 front and 285-35-20 rear winter tire set working on the Carrera S wheels? Seems like it’s not too far off from OEM with some extra sidewall and overall ground clearance.

I can't imagine it would be too much of a problem. Only issue I can think of would be some slight rubbing on larger bumps or potholes. Here are the tire/wheel sizes for the 981 GT4. If this larger than your requested wheel and tires fit on a GT4, then i cant imagine it would be a problem on your car, especially since your car will likely have higher ground clearance than a GT4. It might not rub at all... That's my rational at least...

https://www.suncoastparts.com/product/SKUGT4BLACK.html
 
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FWIW

I’m looking to move to 245/35/20 front and 285/35/20 rear with 20x8.5 ET 45 front and 20x11 ET 40 rear wheels. I will need to get a 15mm spacer for the rear. My current 5mm spacer (currently in rear) I’ll put up front.

This set up reduces my gap about 7mm and variance on speedo is under 3%.

Rippey
 

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Correct -- hence the thread title "aftermarket" instead of "OEM". :D

However, I would be careful regarding aftermarket 987 fitments for two reasons:
- The 1/2" larger rear rim widths
- The change in brake outfitting for the 718:
718 Cayman/Boxster brakes = 987 Cayman/Boxster S brakes
718 Cayman/Boxster S brakes = 991.1 911 Turbo brakes

This is precisely why Porsche OEM 18" rims won't fit the 718 "S" models. That's the big unknown here: those who want to track/AutoX/winter-tire your 718 "S" cars will be hard-pressed to find an off-the-rack aftermarket 18" rim that will work. You'll have to research 991.1 Turbo fitments as a start.
I have 18" wheels on my 718 S. They are Forgestar F14: 18x8.5et55 and 18x10et45. No problems at all for brake clearance. I use these wheels for tracking because there are so many more choices for tire brands and compounds with 18" wheels vs. any other sizes.
 

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Fair warning, this is probably a stupid question!

I've got these laying around, would it work for track days only? I'm sure there's a concern with the fender clearance and it looking pretty weird, but it would save me a ***** for track wheels. Thanks!

Tesla 21" Arachnid wheels:

Size: 21X8.5" front, 21X9.0" rear.
Offset: +40 front, +40 rear
PCD: 5X120
Center Bore: 64.1mm
Weight: 21x8.5" = 27.85 lbs (without tire), 21x9.0" = ~ 28.75 lbs (without tire)
Lug Nut Spec: 13/16 Hex, 14X1.50 Thread
Lug Nut Torque Spec: 129 lb-ft
 

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Fair warning, this is probably a stupid question!

I've got these laying around, would it work for track days only? I'm sure there's a concern with the fender clearance and it looking pretty weird, but it would save me a ***** for track wheels. Thanks!

Tesla 21" Arachnid wheels:

Size: 21X8.5" front, 21X9.0" rear.
Offset: +40 front, +40 rear
PCD: 5X120
Center Bore: 64.1mm
Weight: 21x8.5" = 27.85 lbs (without tire), 21x9.0" = ~ 28.75 lbs (without tire)
Lug Nut Spec: 13/16 Hex, 14X1.50 Thread
Lug Nut Torque Spec: 129 lb-ft

no clue if the wheels would actually fit but i think the biggest problem you would encounter would be finding track tires. not many selections in 21" that i know of. that's why most people stick to 18" wheels.
 
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