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Discussion Starter · #1 · (Edited)
First off let me say, I'm going into this with limited expectations on competitiveness of a Boxtser S 981 in Super Street. Running against a GT3 (and lotus elises) is probably not ideal. Alternatively A Street (not currently classed in A Street but is technically the next class down) is even faster nationally than Super Street with Z06 corvettes (C5 and C6).

That being said, I got this '13 Boxster (PDK, PTV, PASM, Sport Chrono) for DD duty and would like to run it as a back up autocross car when my dedicated RX7 is broken.

Wheel Limitations: the rules allow ±1in in wheel diameter from factory option wheel sizes. OEM wheel widths must be maintained. Lastly the offset can vary by ±7.00 mm (±0.275”). What was the widest wheel offering from the factory? And for that wheel, what was the diameter and offset?

Tire limitation: Tire sizes are unlimited but should not rub expect in a very rare and irregular race situation (full opposite lock slide over a bump).

Hankook RS3 V2's are the most competitive all around tire (expect in the rain) and they seem to offer several sizes in the allowed Boxster wheel range (OEM 19 & 20 and -1in at 18in):

235/40ZR18 91W

235/45ZR18 94W

245/40ZR18 97W

255/35ZR18 90W

265/35ZR18 97W

265/40ZR18 97W

275/35ZR18 95W

285/35ZR18 101W

235/35ZR19 87W

245/35ZR19 89W

245/40ZR19 94W

275/35ZR19 96W

305/30ZR19 102W

255/40ZR20 97W

285/35ZR20 100W

305/35ZR20 104W

Alternatively, The BFG Rival (V2 pending release) are designed for camber challenged cars (like to Boxster) and may work well, but are not proven to be a winner. Sizes available are:

245/40ZR18 93W

275/35ZR18 95W

315/30ZR18 98W

335/30ZR18 102W

255/40ZR19 100W

285/35ZR19 99W

265/35ZR20 99W

285/35ZR20 100W

315/35ZR20 110W

For race sizing, I would ideally like to go as wide as possible without rubbing. What is that threshold on OEM wheels? For overall diameter, I would like to go as short as possible because it will shorten the gearing for acceleration and lower the center of gravity. On the down side the lower car may rub on the NYC bumps during DD and mess with the "look" of the car ie fender gap.

Lastly, for alignment, what is the max OEM negative alignment called for in the service manual front? rear? What toe figures do people run on mid engine boxster. My experience tuning Front Engine RWD, I usually set 1/8in total toe in the rear and 1/8in toe out in the front. Since the car will be DD, I'll probably go a little more mild, but not sure as this is a totally new chassis for me.

Thanks to anyone for pitching in some ideas and experience.
 

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You'll be surprise that the 981S is very competitive against Lotus, GT3, Corvette, on the autocross. I've let some of the better drivers drove my car on the autox and they able to get amazing time. They able to beat those cars so it's the driver more than the car. Max out your camber, my car had PASM and the suspension is settle so I able to get -1.75F and -2.0R. Set rear toe to 1/16 in and front 1/16 out and I think you will have amazing setup. For the tire size I would do RS3 245/35ZR19 and 275/35ZR19. I rather do 245/40ZR18 and 275/40ZR18 but RS3 doesn't offer the rear size. I had no experience with running anything wider but I know there is a guy running 285 or 295 rear on 981 but don't remember the exact setup.
 

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You'll be surprise that the 981S is very competitive against Lotus, GT3, Corvette, on the autocross. I've let some of the better drivers drove my car on the autox and they able to get amazing time. They able to beat those cars so it's the driver more than the car. Max out your camber, my car had PASM and the suspension is settle so I able to get -1.75F and -2.0R. Set rear toe to 1/16 in and front 1/16 out and I think you will have amazing setup. For the tire size I would do RS3 245/35ZR19 and 275/35ZR19. I rather do 245/40ZR18 and 275/40ZR18 but RS3 doesn't offer the rear size. I had no experience with running anything wider but I know there is a guy running 285 or 295 rear on 981 but don't remember the exact setup.
Sorry to go a bit off topic, but would those settings work on a PASM equipped 987.1?
 

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Discussion Starter · #4 ·
Based on current 2015 Boxster S wheel offerings, it looks like this is the widest offering:

"8.5 x 20 ET 57 with 235/35 ZR 20 tires (front)10 x 20 ET 50 with 265/35 ZR 20 tires (rear)"

this is was offered under both Turbo Design wheels and SportTechno

was the same available in 2013?
 

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Sorry to go a bit off topic, but would those settings work on a PASM equipped 987.1?
The toe setting would work but you have less negative camber on 987. The owner at West End Alignment said for autocross you want 0 to slight toe out in front and for track you would want 0 toe out.

Based on current 2015 Boxster S wheel offerings, it looks like this is the widest offering:

"8.5 x 20 ET 57 with 235/35 ZR 20 tires (front)10 x 20 ET 50 with 265/35 ZR 20 tires (rear)"

this is was offered under both Turbo Design wheels and SportTechno

was the same available in 2013?
235/265 F/R with ratio 45/40/35 for 18/19/20 wheels are the same for all 981. You can safely go 245/275 F/R without any problem. I run 245/40ZR18 and 275/40ZR18 (instead of 45 series) and they are almost 1 inch shorter in diameter overall as compared to OEM. Many 981's guys use this configuration. The overall affect is a little wider rubber, 1/2 inches lower, and a little more torque.
 

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Discussion Starter · #6 ·
Qhb, I was mainly asking because I need to verify the widest OEM wheel offered on my car. Did my 13 get offered with 20x8.5 fronts? and 20x10in rears? If so same offset as these ? 57 f / 50 r?
 

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I set our 981 Cayman S to be within the SCCA SuperStreet class. I went for Dunlop ZII tires as that's what I was used to, they're pretty competitive in cooler temperatures. (Which is just about every where we run except Crow's Landing and Thursday at Nationals last year.) I've been wondering about RS-3 as my competitors were doing very well on them last year. This year (2015) ZII star spec might be the way to go.

The widest wheel option the Cayman had was:

20 x 8.5 ET 57
20 x 10 ET 50

So I looked for some 19x8.5 ET 50 and 19x10 ET 43, the ZII only go up to 19", and smaller offset seems like a good idea. I couldn't find any with the right offset, so I got some custom made from CCW. They recommended SP16R (which aren't actually listed on their website). In their terms a backspacing of 6.75" and 7.25" got the right offset (they're about 51 and 44mm). The rear wheels needed to have the 2" lip (the 3" lip version doesn't clear the rear calipers.)

The ZII (and ZII*) only have two sizes in 19", so I got the 275/35R-19 and 245/40R-19. Next time I have the wheels on I need to work out how much clearance they have, so how much of a bigger tire could fit.

I still need to work out what a good alignment is for the car. I ran the first (and so far only) autocross with the stock alignment. I was surprised that the front tire temperatures looked just about perfect without dialing in any additional camber, so I didn't go crazy with the camber. I haven't found out what the max camber is up front, but the shop had no problem putting in 1.5°. I think there's more available. The car has the X73 suspension (as well as all the other goodies, PTV, PDK and Sports Chrono.) The alignment I got is:

Fr toe. Zero
Fr camber 1.5°

Rr toe 1/16" (total, 1/32" each side)
Rr camber. 1.8°

I'm still learning how to drive a rear drive car, so I'm not expecting much from this year, except fun. (But its always good to have a well setup car.)
 

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Discussion Starter · #8 ·
btwyx, Thanks for the feedback. What year is your cayman 981? Your experience in SS prep is priceless for me. I've always been a huge fan of Dunlops Z1 and Z2s. It'll be interesting with the new star spec z2s. Regarding tire size, I'm very interested to see your tire clearances with the above set up in photo form between the strut and tire/wheel front and back. I took some photos today of the OEM clearance. I'll post shortly fwiw.

I came across these Sport Edition Cup 4 on Tire Rack. They look pretty lame but the sizes would (almost) be SS legal if the above referenced wheels were offered on the 2013. They rears would just need to be machined/shaved 1mm. For the price, it'll still be $1k less than CCWs, albeit ugly.

[TABLE="width: 100%"]
[TR]
[TD][h=3]Sport Edition Cup 4[/h] [/TD]
[/TR]
[TR]
[TD] Front
  • • Size: 19x8.5, 54mm Offset
  • • Price: $222 (each)
  • Est. Availability: In Stock
  • • Weight: 26.4lbs.

Rear
  • • Size: 19x10, 42mm Offset
  • • Price: $228 (each)
  • Est. Availability: In Stock
  • • Weight: 29.6lbs.



  • • Finish: Silver Painted
  • • Bolt Pattern: 5-130
  • • Construction: 1pc. Gravity Cast

[/TD]
[/TR]
[/TABLE]
 

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We have a 2015, delivered in August so we haven't had much chance to play yet. I don't have much experience prepping for SS, last year I prepped an HS MINI (the car managed the 6th fastest time when it was cooler on Friday at nationals), but I've only been doing this a couple of years.

You link doesn't work, but the Sport Edition Cup 4 wheels I can find are 18x8/18x10 which would not be a legal combination. Wheel options was one thing I made sure to make notes of, even take screen shots from the configurator to be sure. The options I had were:

8 x 19 ET 57 with 235/40 ZR 19 tires (front)
9.5 x 19 ET 45 with 265/40 ZR 19 tires (rear)


8 x 20 ET 57 with 235/35 ZR 20 tires (front)
9.5 x 20 ET 45 with 265/35 ZR 20 tires (rear)


8.5 x 20 ET 57 with 235/35 ZR 20 tires (front)
10 x 20 ET 50 with 265/35 ZR 20 tires (rear)

The 8.5/10 ones are the Sport Techno wheels. I don't know when they were available as an option.
 

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The Sport Techno were an option for the 2013 Boxster's. Not the Turbo wheels.
 

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Discussion Starter · #11 ·
Anyone run 255/35/19 up front on 19x8.5s? Any clearance issues to consider? What offset?

The
255/35R19 is a available size in the new magic "Hoosierstones" AKA Bridgestone RE71R. I got a screw through a rear tire now so I am using this as an opportunity to get race wheels and tires with the new Re71rs
 

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I run 245/40ZR18 and 275/40ZR18 (instead of 45 series) and they are almost 1 inch shorter in diameter overall as compared to OEM. Many 981's guys use this configuration. The overall affect is a little wider rubber, 1/2 inches lower, and a little more torque.

Qhb, in some other thread you mentioned (last year) that you just use 18" wheels from 987 Cayman. How do they work for you? They are 8" and 9" wide if I remember correctly. Do you see any significant "bulging" from 245mm and 275mm tires?

I just picked up my Cayman GTS a week ago. New to Porsche and this forum (first post here but kept reading it for some time). My track/autox car is Subaru STI which is completely different animal. :) Planning to track and AutoX Cayman after the break-in period.
 

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Qhb, in some other thread you mentioned (last year) that you just use 18" wheels from 987 Cayman. How do they work for you? They are 8" and 9" wide if I remember correctly. Do you see any significant "bulging" from 245mm and 275mm tires?

I just picked up my Cayman GTS a week ago. New to Porsche and this forum (first post here but kept reading it for some time). My track/autox car is Subaru STI which is completely different animal. :) Planning to track and AutoX Cayman after the break-in period.
245 & 275 on Cayman S wheels fit perfectly with no bulging. It's a great setup and the tires are cheaper and the car handles great. If you run 235/265 40R18 you have the option of RE-11, R-S3, and AD08. To run 245/275 40R18 you only have RE-11. The limit width prevent you from going any wider and even if you want to you don't have any tire option in 18.

I changed my race class this year from SS06 to CC09 even-though I won the series two years in a row in SS06. The class CC09 has very stiff competition as people are running slick and heavily modified cars but I need to complete with these guys for me to get any better. Well, I got my b*tt kicked really good so I am upgrading my wheels and tires.

The new setup I am contemplating is O.Z. Leggera HLT - 19x8.5 and 19x10 (debating on 19x11 but spacer may be needed) with Bridgestone RE-71R size 255/35R19 and 275/35R19 (almost square setup). I want 285/35R19 but it's not available for RE-71R and I don't want to use RE-11 as RE-71R supposed to be quite a bit better.
 

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245 & 275 on Cayman S wheels fit perfectly with no bulging. It's a great setup and the tires are cheaper and the car handles great. If you run 235/265 40R18 you have the option of RE-11, R-S3, and AD08. To run 245/275 40R18 you only have RE-11. The limit width prevent you from going any wider and even if you want to you don't have any tire option in 18.
Qhb, thank you for the info! What tires do you currently run on 18"? Yeah, I'm not sure if I should get 18 or 19". 18" will allow me to run NT01 if I wan too and tires are cheaper but 19" has wider selection of EP Street tires but no selection of R-comps except maybe MPS Cup tires which are really expensive. At this point I probably want to run AD08R, re-71R or RS-3 tires.

Is there a big downside in running 265/40-18 instead of 275/40-18? From what I know front/rear overall wheel diameter ratio matters in these cars and 245/275 combo will keep it similar to stock but 245/265 will be a bit off with the lower rear. Same situation with 255/275 combination on 19" rims (i.e. for RE-71R). Not sure if that difference matters...

BTW, do you or anyone here have any experience with re-71R? I'm really interested to hear about first hand comparisons to AD08R or RS3.

My personal experience with different tires: Z1 SS, AD08 (older, non-R), RS-3 and NT01. Among Street EP tires Z1 SS were the least favorite and Rs3 were the most favorite. AD08 were in the middle. But that was with nose heavy AWD vehicle and square setup.
 

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I run RE-11 on my 18-in size 245/40R18 and 275/40R18.

A member here run MPSS 245/35-20 and 285/30-20 http://www.planet-9.com/porsche-tires-wheels/104412-245-40-20-275-40-20-tires-981-a.html#post916193. If you calculate the diameter you will see that front and rear are the same so I think 245/265 or 255/275 should be OK.

I still haven't pull the trigger yet, even though I sold my 18-in wheels, as I am waiting a few more week hoping for a miracle that 285 be available on the RE-71. My next track day is in May so I have to decide soon.
 

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I run RE-11 on my 18-in size 245/40R18 and 275/40R18.

A member here run MPSS 245/35-20 and 285/30-20 http://www.planet-9.com/porsche-tires-wheels/104412-245-40-20-275-40-20-tires-981-a.html#post916193. If you calculate the diameter you will see that front and rear are the same so I think 245/265 or 255/275 should be OK.
Thank you! According to my tire calculator in stock size (235/35-20 and 265/35-20 for me) rear wheel is 3.1% bigger on overall diameter than the front one. 245/40-18 and 275/40/18 have the difference of 3.7% which is very close. 245/35-19 and 275/35-19 - 3.2% - almost like OEM set. 255/35-19 and 275/35-19 - 2.1% also not that far off. For re-71R in 18" we have 245/40-18 and 265/40-18 ->2.4% which should be OK. Also for 18" we have (for re-71R) 245/40-18 and 275/35-18 with negative 0.5% Rear to Front difference and that's a bit too much I guess? 3.7% different from factory R/F ratio....

As you mentioned a member here runs 245/35-20 and 285/30-20 (R/F). That looks like negative 0.1% So yeah if he's OK then any combination above (maybe except 245/40-18 and 275/35-18) is OK.

I still haven't pull the trigger yet, even though I sold my 18-in wheels, as I am waiting a few more week hoping for a miracle that 285 be available on the RE-71. My next track day is in May so I have to decide soon.
You're on stock suspension, right? Does 285 fit with no issues?
 

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For autocross (in the previous cars) I found I was considerably quicker on other tires like BFG Rivals or Dunlop ZII than the RE-11. I like RE-11 as track tires.
Btwyx, you mentioned earlier that you run 245/40-19 and 275/35-19 (only sizes for Z2 SS available in 19"). That's negative 0.5% R/F ration (fronts larger in diameter). Have you encountered any issues with this ratio?

BTW, how long did it take you to get custom CW rims?
 

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Btwyx, you mentioned earlier that you run 245/40-19 and 275/35-19 (only sizes for Z2 SS available in 19"). That's negative 0.5% R/F ration (fronts larger in diameter). Have you encountered any issues with this ratio?
I've never had a problem with it that I've noticed. Somewhere around here there's a chart of tire options and this is noted, but that no one else seems to have any problem either.

BTW, how long did it take you to get custom CW rims?
I think the quote 4-6 weeks. They arrived the week after I ordered them.

By the way, Bridgestone RE-71R are shaping up to be the popular Autocross tire this year. They were on lots of them at the Crow's Landing tour this weekend. They won BS, CS, FS, GS, HS and all the Street Touring classes. There was a report that one car gained a whole second on the practice course by switching to Bridgestones from one of the other usual suspects. They're available in the 245/40-19 and 275/35-19 sizes.
 

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I've never had a problem with it that I've noticed. Somewhere around here there's a chart of tire options and this is noted, but that no one else seems to have any problem either.


I think the quote 4-6 weeks. They arrived the week after I ordered them.

By the way, Bridgestone RE-71R are shaping up to be the popular Autocross tire this year. They were on lots of them at the Crow's Landing tour this weekend. They won BS, CS, FS, GS, HS and all the Street Touring classes. There was a report that one car gained a whole second on the practice course by switching to Bridgestones from one of the other usual suspects. They're available in the 245/40-19 and 275/35-19 sizes.
I got a few emails with [email protected] and he told me that the wheels that I want, O.Z. Leggera HLT, will come in black in June so I am pulling the trigger to order this wheels in 19-in with RE-71R 255/35R19 and 275/35R19.
 
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