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Old 02-14-2018, 05:06 PM
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Audioi
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Default Optimum wheel size

Have a 2013 981 base with 18's and really like the looks of the 20" classics but others have said it will ruin the ride? Its a weekend car for casual use, no track, suggestions??
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Old 02-14-2018, 05:32 PM
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I'd go 20's or 19's. My car came with 20" classics (that I may be willing to sell if you are interested, since I want smaller wheels for the track), and they really don't ride that rough to me. More meat on the tires will clearly ride somewhat better, but I think it is a vast over generalization to say it "ruins" the ride. The cars ride stiff, by design. 20's look best, 18's ride best, 19's are in the middle. I'm looking for 18's or 19's for the track, but have been plenty happy on the street with my classics.
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Old 02-14-2018, 07:03 PM
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The 20"s make the car look very aggressive. I agree with PorscheAddict that they look best among all available sizes. As for ride, they are not bad at all IMHO. The ride is just firm even when I set my PASM to Sport, way far from being harsh. I'm switching from one set of 20"s (Carrera Classic) to another 20"s (Turbo) with no reservations.



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Old 02-14-2018, 09:12 PM
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There's no optimum: everything is a tradeoff. The short version is big wheels for show, small wheels for go.

Bigger wheels can look good. However, 20s are going to be heavier than your 18s, plus they'll have the mass closer to the outside so they have a higher moment of inertia (they take more energy to turn, essentially.) These are not good things for unsprung weight, handling, or acceleration. 20s also have shorter sidewalls so they'll ride harsher, and this can affect grip on non-smooth pavement: tires that are bouncing around aren't doing a good job of sticking to the pavement (I have been told anecdotally that if you set PASM to sport with 20" wheels you'd better be ready for the car to jump into the next lane on a rough highway.)

My 987.2 came with 19s and they look really good on the car, but there's many a day I've been driving on not-so-great roads really wishing it had had 18s. Knowing what I know now, if I were you there's no way I'd go from 18s to 20s. But you need to decide what's important to you in the car.
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Old 02-14-2018, 10:51 PM
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Originally Posted by MrMoose View Post
There's no optimum: everything is a tradeoff. The short version is big wheels for show, small wheels for go.

Bigger wheels can look good. However, 20s are going to be heavier than your 18s, plus they'll have the mass closer to the outside so they have a higher moment of inertia (they take more energy to turn, essentially.) These are not good things for unsprung weight, handling, or acceleration. 20s also have shorter sidewalls so they'll ride harsher, and this can affect grip on non-smooth pavement: tires that are bouncing around aren't doing a good job of sticking to the pavement (I have been told anecdotally that if you set PASM to sport with 20" wheels you'd better be ready for the car to jump into the next lane on a rough highway.)

My 987.2 came with 19s and they look really good on the car, but there's many a day I've been driving on not-so-great roads really wishing it had had 18s. Knowing what I know now, if I were you there's no way I'd go from 18s to 20s. But you need to decide what's important to you in the car.
MrMoose, I hope you know I respect your opinion. You have helped me a lot in a couple of issues here and I sincerely appreciate that. However, with all due respect, I have to argue a little regarding this particular topic. While what you stated are all correct: 20s being heavier and the mass closer to the outside and all, but those are trivial facts at best when it comes to street driving. Yes, 20s may be heavier by 2 lbs per corner (but the tires are slightly lighter due to the lower profile), but the 8-lb difference is very hard to be felt in street driving even by an advanced driver. If one is chasing one-tenths of a second on the track, yes, 8 lbs matter. However, in street driving, I don't think it does. Regarding 20s tend to stick further to outside, there are a lot of racers who use spacers in sake of fitting wider wheels/tires sacrificing a higher MOI for greater grip. I am coming from 12 years of SCCA national-level autocross with a CSP Miata and Formula Ford. I think I know what I am talking about.

Regarding what you heard "if you set PASM to sport with 20" wheels you'd better be ready for the car to jump into the next lane on a rough highway", I can attest that is not true. I have driven my 2015 BS on 20s with PASM set to sport in many occasions on notoriously bad New Jersey roads with no problem at all. Yes, it feels firm, but way far from being "harsh".

It is my honest opinion that, while they look really great, 20s don't take anything away from your driving experience. YMMV.
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Old 02-14-2018, 11:26 PM
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As always, we must suffer for fashion.
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Old 02-15-2018, 01:00 AM
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I thought the same thing prior to getting my 13 Boxster. My friend had “inherited” an Acura with 20” low profiles that rode terribly here on our unrepaired SoCal streets and roads. So when I was shopping for my Boxster, I was kinda wishing I could find the right one with 18 or 19’s. But of course, I found the car I wanted and it had 20’s. Amazingly, I don’t regret it at all and am glad I got them. Both driving around town on very rough streets and on a week long cross country trip, they’ve never felt harsh by any means. Sure, not as soft as my BMW 5, but nowhere near as rough as my friend’s Acura.
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Old 02-15-2018, 01:05 AM
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I hear you, storii. And you're right, the weight and inertia differences may be small (though I can tell you I've gone both ways on unsprung weight in street cars and can definitely feel even a few pounds difference in the ride. It's probably more noticeable on a rough road than a smooth track.) But the thing you can't get around is the shorter sidewall in a big wheel, and that makes a big difference in ride. I don't have a glass backside but, man, the 19s are annoying some days. Maybe our roads are worse than yours.

18s are going to ride better than 20s, really no question about that. And the only performance you're going to get from 20s on the street is in the eyeballs department. So the question on a road car is whether you want the better ride or you want the looks: I know what I'd do, but plenty of folks make the opposite decision.
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Old 02-15-2018, 01:57 AM
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Check Youtube for the Top Gear test where the same car was slower on the track with low profile tyres.
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Old 02-15-2018, 07:08 AM
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Interesting debate i went over with my 987 non pasm with 18” wheels . Was too harsh on uk roads .
I had a chance of some 17” wheels cheap and bought . Very noticable improvement
in ride quality and seemed to suit the car better .

When i was looking for a 981 i really wanted 19” wheels but the right car turned up with
20” and i tried that and surprisingly the ride is great ! It has pasm and im sure other factors
come into play such as tires , but the upshot is to try before you buy .
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Old 02-15-2018, 11:06 AM
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One more thing I want to point out is that, for the 981, Porsche made 20" wheels factory option for the first time in the Boxster history. This may have something to do with the fact that many feel the ride in a 981 on 20s is not harsh at all.
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Old 02-15-2018, 11:14 AM
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Audioi
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All good points!
I really dislike the look of the high profile tires on this car but reasoning with upstate NY potholes is difficult. My wife bent 2 wheels on our ATS a couple years back with ease, guess thats something to consider.
Then again I look at it every day when I come home, decisions...
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Old 02-15-2018, 12:06 PM
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The CSIII 20s fill out the car nicely, this set-up has the X73 suspension installed, helping with the wheel gap and some spacers. As for ride, 20s are completely compliant and not harsh in any way, just sporty in feel. If your area has a lot of potholes and bad roads, 20s would not be a good idea.
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Old 02-15-2018, 02:15 PM
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Had a ‘14 981 base and went from stock 18’s to CSIII 20” wheels. Not a big trade off in ride but did notice slightly less sharp acceleration/general dynamics but the 20” fill out the 981 wheel wheels surprisingly well. I thought they would look too big but they looked f’n killer. Just picked up a 987.2 and ironically I think 20’s look too big on that car. But on the 981, for me, the 20” really made the car look amazing and we’re well worth the slight dynamic degradation from the additional unsprung weight.
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Old Yesterday, 07:46 PM
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storii
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Finally got around to mount the new (to me) 20" wheels. Had to wait until the salt on the roads got washed away and for a reasonablly warm day since the car needs to be driven for the TPMS to "learn" the new wheels. Got it all done before tonight's snow storm!


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