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Drove 2 2015 base Caymans. One with 19 inch wheels one with 20 inch wheels. Not taking into consideration the looks, do the 19's handle better. By better I mean more responsive and "sharper" steering. Tires were the same.
 

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Can't tell you FOR SURE, but I have 19s and 18s with the same rubber and I could not tell you which whiles were on the car in a double-blind test.
 

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I'd like to be better informed about this choice too.

Perhaps I'm just guessing wrong here but I've always believed the lower profile tire will corner better at the limits due to less sidewall flex, so the 20" must have some improvement. However the trade off would seem to be harshness of ride on bad roads. What about length of service?


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Personally I like bigger wheels more. Could be psychological, but bigger wheels feel more responsive. Air compresses, while metal doesn't. But I really wouldn't wanna run anything below 35 profile, or maybe even 30 at the absolute most on these cars.

Some argue smaller wheels have less unsprung mass, but that's something hard to measure really. You could argue that the smaller wheel has more mass closer to its center, while bigger wheels have their mass stretched closer to the end of the tire. Weight-wise, the 20" might not save you much as you do end up pumping more air.

I'm sure someone has done it, but it's worth a look to weigh two wheels of same design (one 1" smaller in diameter) including having their respective tires pumped up to same pressure. I know weight doesn't mean a whole lot compared to unsprung mass.

Some do go into smaller wheels (i.e. 18") just because of cost and tire selection due to track use.
 

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Porsche rally Ace Walter Rohrl set the record for a 981 CS at the Nurburgring: 7:55 with 19 inch wheels. He was asked about using 20 inch wheels on the 981 CS at the Ring: “Their advantage on a lap of the Ring is about two, maximum three seconds. However, they have no added benefit on public roads apart from their looks, so on balance I would go with the 19-inch wheels as the best all-round option for daily use.”
 

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People keep kicking this dead horse. Over. And over. And over again.

Bottom line is 1 inch isn't going to make much (if any) difference. If you compared 15 inch vs 20 inch (same wheel + tire size), the 20 inch wheels would handle better. The car would veer off less due to sidewall flex, but this means the wheels are less tolerant, where the 'softness of rubber' isn't 'smoothing out' where the wheels go. Means you have to work harder to get the car where you want it too and sometimes you get less traction as the sidewall doesn't flex enough.

Also note that the MPG/ speed of wheels is not a factor beyond the weight, tire choice, and tire pressure (for the same rim+tire size). If you increase the overall wheel size (rim+tire and maybe wider), you will get slower acceleration and worse MPG.
 

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this thread theme is on every forum.

its a personal preference.

less sidewall could provide some better performance - but you will feel more on harsh roads.

smaller wheels could leave more wheel gap.

this preference is probably based on age too.

;)
 

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Yes, and to reinforce the age thought, I am 68 and therefore prefer 16" wheels :). I had 18" on my 08CS, 19" on my Cayman R and 19" on my 981. I think the 19s fill the wheel opening a bit more and therefore like them and do not feel much in compromised ride with them.
 

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I think the 19s fill the wheel opening a bit more and therefore like them and do not feel much in compromised ride with them.
If you're talking about fender gaps, then it makes no difference. Both have the same diameter tires so the "wheel opening" is filled the same amount in both cases. Now... if you're referring to the amount of that area that's filled with wheel vs. with tire, then you have a point. That's why people tend to like the look of bigger wheels. Wheel is prettier than tire.

Honestly... given that the performance difference is negligible and I don't much care what others think, I'd opt for the smallest available wheel simply because it lowers the risk of bending a wheel on a pothole or something and lets you buy less expensive tires. :)
 
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What are the specified tire sizes for the two wheel diameters?
 

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Yes, and to reinforce the age thought, I am 68 and therefore prefer 16" wheels :). I had 18" on my 08CS, 19" on my Cayman R and 19" on my 981. I think the 19s fill the wheel opening a bit more and therefore like them and do not feel much in compromised ride with them.
I'm 68 and I prefer 20" wheels. :)

My previous Cayman had 18" and 19" wheels. Although the wheels had the same brand summer tires I used the 18" wheels in the winter and the 19" wheels in the summer. The 19" wheels handled better but had a rougher ride. Now I have 20" wheels and they handle better but ride even rougher. My next Cayman will have 19" wheels which I feel is a good compromise for ride and handling.
 

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I'm surprised some think the 20s ride rough. I was going to get 19s on my 981CS but didn't like the style so went with 20s. I'm really surprised how well the car rides with 20s and PASM set to normal (not sport). Even in sport it's not bad. Someone had also posted weights of wheel/tire combos and the Carrera S combo is fairly light for OEM wheels (actually lighter than the 19s so less unsprung mass9:

http://www.planet-9.com/porsche-tires-wheels/87828-type-981-porsche-oem-wheel-weights-need-sport-techno-weights.html
 

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^^interesting point.

I hope i can get in one of these cars when I'm in my 60's.

my kids laugh at me at the noises i make when getting in and out of my car.
 

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I know weight doesn't mean a whole lot compared to unsprung mass
en.wikipedia.org/wiki/Unsprung_mass
In a ground vehicle with a suspension, the unsprung weight (or the unsprung mass) is the mass of the suspension, wheels or tracks (as applicable), and other ...

Rink
 

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Personally I like bigger wheels more. Could be psychological, but bigger wheels feel more responsive. Air compresses, while metal doesn't. But I really wouldn't wanna run anything below 35 profile, or maybe even 30 at the absolute most on these cars.

Some argue smaller wheels have less unsprung mass, but that's something hard to measure really. You could argue that the smaller wheel has more mass closer to its center, while bigger wheels have their mass stretched closer to the end of the tire. Weight-wise, the 20" might not save you much as you do end up pumping more air.

I'm sure someone has done it, but it's worth a look to weigh two wheels of same design (one 1" smaller in diameter) including having their respective tires pumped up to same pressure. I know weight doesn't mean a whole lot compared to unsprung mass.

Some do go into smaller wheels (i.e. 18") just because of cost and tire selection due to track use.
have a 2015 Catman GTS, cane with 20" wheels, very few DE tire options...so I put my pals 18" 2009 Cayman S wheels on today, his fronts are 8 1/2 " wide, the rears are 10".O.Z. Allegrittas and running Hoosiers. The front tires have about 1/2" of clearance to the front struts, the rears look so tiny.....I am going to 19", 235/40/19, 265/40/19...maybe even a 35 profile.
 

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So i actually weighed my 18 inch rims (with tire) and my 20 inch (with tire). The 18s were the cheapest rims you couod buy a 981, the 20s are the carrera classics style 10 spoke alloy rims.

The 20s weighed LESS than the 18s. It was about 3lb in front and 5 in back if i remember right. The 20s were lighter.
 

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So i actually weighed my 18 inch rims (with tire) and my 20 inch (with tire). The 18s were the cheapest rims you couod buy a 981, the 20s are the carrera classics style 10 spoke alloy rims.

The 20s weighed LESS than the 18s. It was about 3lb in front and 5 in back if i remember right. The 20s were lighter.
Something else to consider is rotational inertia. Extending the mass an extra two inches from the center of rotation must make it harder to accelerate and turn that spinning assembly, though I have no idea whether that effect is greater or less than the reduction in unsprung weight.
 

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Given that the 19's you listed were 40's and the 20's were 35; the 20's would handled better based on the tire's sidewall response.
The 19" 40's would ride better as there would be more shock absorbing in the 40 sidewall than the 35 but
If want to fully compare you need to use all of the spec's - mounted weight of each setup, tire diameter, price of each setup plus the tire sidewall
If it were me I would go with 19" using 35 tires. The 19" tires & probably also the wheels are usually cheaper than 20's that's why I use 18" instead the stock 20's on my car.
 
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