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I am looking at a set of winter tires for my 2012 CSBE. I currently have a winter setup with stock 987.1 CS wheels and correct winter tires, but the tires are nearing the end of useful life. I found a winter set of tires that were used on a 981 and although they have the same width and diameter as the standard 987 summer tire they are 45 series where the stock 987's are 40's.

Stock 987CS tire: Front 235/40 18 Rear 265/40 18

981 winter tire: Front 235/45 18 Rear 265/45 18

I understand the speedometer will no longer be accurate, but will there be any problems with the traction control or skid regulation due to the non standard sizing? Thanks for the help.
 

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I have 981 and for the track I ran 987 size 235/40 18 Rear 265/40 18 then 245/40 18 Rear 275/40 18 and had no problem. The overall diameter will be 1 inch taller so your ground clearance will be +1/2, gap between tires and wheel well be smaller so it will look better, your speedometer will be off by about -3MPH at HWY speed, you'll will lost a few ft-lbs of torque (doubt if you can tell), and that's it. If they fit your your car and price is right then go for it, I would with no reservation.
 

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When going up a size, you will want to watch for rubbing particularly at full lock left & right. Hopefully +1/2" isn't a problem, but the tire does flex and distort under loads too.


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I found some 18" Nokian R2's but need some help with the aspect ratio. My choices for up front are 235/40/18, 235/50/18 and 235/45/18. On the rear, it's pretty much 255/45/18. I was thinking go 50 in the front and 45 in the back, but is that correct? That puts front diameter at 27.25" and rear at 27.04". Thanks.
 

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I found some 18" Nokian R2's but need some help with the aspect ratio. My choices for up front are 235/40/18, 235/50/18 and 235/45/18. On the rear, it's pretty much 255/45/18. I was thinking go 50 in the front and 45 in the back, but is that correct? That puts front diameter at 27.25" and rear at 27.04". Thanks.
If it's of any help, the old 987 Car's recommended 18" winter tire fitment were 235/40 x18 Fronts, 255/40 x18 rears - basically the @26" diameter choices. 265/40 rears were also "OK"

Up sized to the new 981 @27" diameter tire speds, IMO that should translate into 235/45 x18 Fronts, & either 255/45 or 265/45 rears, whichever sizes you can get your snows of choice delivered in.
The R2 looks like it ought to be an awesome both snow & ice tire.
 

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If it's of any help, the old 987 Car's recommended 18" winter tire fitment were 235/40 x18 Fronts, 255/40 x18 rears - basically the @26" diameter choices. 265/40 rears were also "OK"
That is why I have some concern - I should have mentioned that these are for a 987.2 S. The only close rear choice is 255/45 in the Nokian R2. The Michelin dealers have only the PA-2 available and those tires are literally almost three years from their production date. I'm not a fan of Blizzaks and Pirelli Soto 2 is the only other choice it seems.

The 255/45/18s for the rear are 27.04" in diameter, which is 2.7% bigger than the 265/35/19s. For the front, the 235/50/18s are closest in diameter to the 255/45/18s, but are a shade larger at 27.25". Going with the 235/45/18s in front, the diameter is 26.33". I'm looking for the magic number so the ABS, etc. is not affected adversely. So it boils down to - are the 255/45s too large in diameter, and if not, are the 235/50s?
 

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That is why I have some concern - I should have mentioned that these are for a 987.2 S. The only close rear choice is 255/45 in the Nokian R2. The Michelin dealers have only the PA-2 available and those tires are literally almost three years from their production date. I'm not a fan of Blizzaks and Pirelli Soto 2 is the only other choice it seems.

The 255/45/18s for the rear are 27.04" in diameter, which is 2.7% bigger than the 265/35/19s. For the front, the 235/50/18s are closest in diameter to the 255/45/18s, but are a shade larger at 27.25". Going with the 235/45/18s in front, the diameter is 26.33". I'm looking for the magic number so the ABS, etc. is not affected adversely. So it boils down to - are the 255/45s too large in diameter, and if not, are the 235/50s?
So, to be clear, this is really a two part question. A, are the sizes close enough to avoid ABS/TCS/PSM confusion?
My guess is, by being within 2.7%, from what little I know, the tires are close enough.

The second part, i.e. is going up @ 1" in diameter going to cause a problem? I don't know. I have not had any problems (other than having to be extra careful with ground clearance) going DOWN a section size, i.e. running 235/40 x18 tires on a 981 which would normally call for 235/45 x18's, but going up a section size isn't something I've done. My guess is, there shouldn't be an issues with the rear 255/45 x18's, as for the fronts, if you had rubbing issues, it would occur be at full lock turn ins, and that's hard to determine statically. One would "think" Porsche would have provide at least a 1/2" margin of additional clearance, . . . . . but that's only a guess on my part.

For wheel well clearance issues, it seems like it can be easier to "know" where you are going down in diameter, the going up.
One would think a half inch wouldn't matter - but I don't think one knows till you have the tire on the car, turned in under load in both directions and that's hard to do on a static test fitting.
Best of luck.
 

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So, to be clear, this is really a two part question. A, are the sizes close enough to avoid ABS/TCS/PSM confusion?
My guess is, by being within 2.7%, from what little I know, the tires are close enough.

The second part, i.e. is going up @ 1" in diameter going to cause a problem? I don't know. I have not had any problems (other than having to be extra careful with ground clearance) going DOWN a section size, i.e. running 235/40 x18 tires on a 981 which would normally call for 235/45 x18's, but going up a section size isn't something I've done. My guess is, there shouldn't be an issues with the rear 255/45 x18's, as for the fronts, if you had rubbing issues, it would occur be at full lock turn ins, and that's hard to determine statically. One would "think" Porsche would have provide at least a 1/2" margin of additional clearance, . . . . . but that's only a guess on my part.

For wheel well clearance issues, it seems like it can be easier to "know" where you are going down in diameter, the going up.
One would think a half inch wouldn't matter - but I don't think one knows till you have the tire on the car, turned in under load in both directions and that's hard to do on a static test fitting.
Best of luck.
Thanks, mlpor. I am now thinking 235/45 in front, 255/45 in back. That retains the relationship in size front to rear and is only a shade over 27" in diameter. My Porsche shop is checking these sizes with Porsche NA.
 

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Dunlop SP Wintersport 3Ds are another option...they come in the correct OEM 18" winter sizes for a 987.2 (235/40/18 front 255/40/18 rear). Compared to the Sottozeroes they offer a bit more snow and ice bite with only slightly less capable dry weather handling. I currently have the Dunlops on my GTS and decided against the R2s in favor of the Wintersport 3Ds for the 987.2 CS. Tirerack has the Dunlops in stock.
 

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Dunlop SP Wintersport 3Ds are another option...they come in the correct OEM 18" winter sizes for a 987.2 (235/40/18 front 255/40/18 rear). Compared to the Sottzeroes they offer a bit more snow and ice bite with only slightly less capable dry weather handling. I currently have the Dunlops on my GTS and decided against the R2s in favor of the Wintersport 3Ds for the 987.2 CS. Tirerack has the Dunlops in stock.
Really appreciate it - and I went to order these and, guess what, the rear tires in stock are over 2 years old. Wow. No one has fresh tires.
 

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Really appreciate it - and I went to order these and, guess what, the rear tires in stock are over 2 years old. Wow. No one has fresh tires.
Interesting. Not a big concern here, though. Given how much we drive in the winter (each car gets around 5000-6000 winter miles yearly) the tires are only good for a couple of seasons. We get numerous warm spells throughout the winter that melt all the snow and ice on major roads, so even though it's cold, the roads are dry. On dry pavement, winters wear down relatively quickly to 60% tread depth, at which point they begin to lose their effectiveness on snow and ice. Still perfectly acceptable for cold, but not so great through the deep stuff.
 

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Dunlop SP Wintersport 3Ds are another option...they come in the correct OEM 18" winter sizes for a 987.2 (235/40/18 front 255/40/18 rear). Compared to the Sottzeroes they offer a bit more snow and ice bite with only slightly less capable dry weather handling. I currently have the Dunlops on my GTS and decided against the R2s in favor of the Wintersport 3Ds for the 987.2 CS. Tirerack has the Dunlops in stock.
Correct sizing for a 987.2 is 265/40-18 on the rear, not 255.
 

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For summer tires, that's correct. 987.2 Porsche OEM Tequipment winter wheel/tire packages come with 255s on the rear. Porsche Tequipment Cayman (2005-13) en
IIRC, it has to do with extra clearance for snow chains. As for the old tires, I have yet to wear out tires before the 6 year mark here in southern OH, so I will not buy or put 2-3 year old "brand new" tires on the car since they will need to be replaced after 3 seasons. The manual states clearly - under no circumstances should you run with tires that are more than 6 years old.
 
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