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Old 12-03-2009, 12:02 PM   #1
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General consensus on wheel sizes?

Interested in the current views on wheel sizes. Particularly for 987 but not sure if it matters. 17 vs 18 vs 19 All other things equal, does handling noticeably improve going up? Ride quality suffer inversely?

As a former NA miata owner, the younger folk on the forums tried to stuff the largest wheels they could under the wells, but the more "seasoned" enthusiasts tended to agree that really the lower range (say 15's) work the best performance-wise.

Just wondering what the more experienced owners have to say about wheels on a Box.

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Old 12-03-2009, 01:53 PM   #2
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IMHO, the best compromise between aesthetics, ride, performance and cost is 18".

19s and 20s hurt performance and ride while costing a lot more to shoe them, for me, that's not offset by a better aesthetic. In fact, once you get to 20s, you're approaching the Donk range for these cars.

I'm sure there are others who disagree and will chime in with their opinions. That's OK and why America, and this forum, are so great!

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Old 12-03-2009, 02:24 PM   #3
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I have 19z and Lil Bastard is 100% correct!

I used to push hard on here that 19z were the way to go. They look too
big on the car. Looking at the car from the back on an angle, the wheels
don't look good. The rear bumper is too small looking.

18z are the way to go. I've seen 18z on a Boxster and from far could barely tell that they were 18z....looked like 19z.

I will most likely go back to 18z. The overall ride is decent.
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Old 12-03-2009, 03:29 PM   #4
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18's here

I have 18's and they look great...
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Old 12-03-2009, 03:52 PM   #5
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Quote:
Originally Posted by CRCGuy
Interested in the current views on wheel sizes. Particularly for 987 but not sure if it matters. 17 vs 18 vs 19 All other things equal, does handling noticeably improve going up? Ride quality suffer inversely?

Just wondering what the more experienced owners have to say about wheels on a Box.

CRCguy
To be perfectly honest, the only thing that is going to make a difference in the actual performance of the car is the width of the tire. The wider the tire, the larger the contact patch connecting the car to the ground, and offering feedback to the driver.

Wider tires, of course, need wider wheels.
Typically, the tire manufacturers recommends a range of wheel widths to fit their tire of a specific size and construction. And they most likely are not going to offer that same tire size in each and every wheel diameter available, otherwise they would have to make way too many molds for every tire they produce.

Also, a smaller wheel weighs less, and that takes less power and effort to change directions, accelerate, and slow it down once its spinning, which makes the car feel more responsive, and nimble.

I think the best question to ask is what are the tire sizes needed for optimal performance. The original 986 came with 205/55-16 tires in the front, and 225/50-16 in the rear as stock. The optional wheel package came with 205/50-17 up front, and 255/40-17 in the rear. I'm pretty sure everyone will agree that a 986 equipped with the optional wheel/tire package out performed the base wheel/tire setup.

So, what's the ultimate combination of tire sizes for the front and rear for superb handling, yet still retains the car's flick-ability, and driving characteristics? Once we have that, then we can probably figure out the best size wheels to mate those tires to the car.

BC.
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Old 12-03-2009, 06:18 PM   #6
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+1 on 18s. HOWEVER, if you are going the R-compound route, know that it cost me $1350 on 18s VS $850 on the 17s...
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Old 12-03-2009, 09:09 PM   #7
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Thanks! great information guys. It just occurred to me that that one of the reasons I asked is what 986roadster said. I saw a 987 last week with 19's (sport design wheel I think) and it did look a bit out of proportion for some reason but couldn't quite place it at the time. But now that you mention it, you're right, just a touch too big.

Lil bastard: thanks. Didn't even think about the increased tire costs. I don't have my box yet, but when I do, I'm fairly certain I'm gonna go through some tires

Thanks again. Keep 'em coming. But sounds like 18 is a nice compromise--keeping in mind the tire size issue, but sounds like law of diminishing returns as you go any larger.

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Old 12-04-2009, 05:04 AM   #8
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As with most things, it depends on your usage. if you're hard core about Autocross, 17's will probably be best. Will you be doing serious track days, or just spirited street driving/moderate track running? 19's should give slightly sharper steering response, but I don't know that ultimate grip goes up over 18's, which to me have great response, but I've never driven on 19" wheels.

I would suggest test driving cars with each wheel size 17-19", then decide which suites you. The OEM 17" wheels/tires are narrower, so will have less grip than the larger sizes.

Having said that, I think 18's are the best for me, though I would like try a car on 19" wheels.

Steve

P.S. Oh yeah, The highest ultimate grip will come from stuffing the widest tires/wheels possible under the fenders, without raising the ride height, which you would actually want lower, regardless of wheel diameter.

Last edited by stephen wilson; 12-04-2009 at 05:12 AM.
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Old 12-04-2009, 06:22 AM   #9
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It all boils down to physics. Turning is a product of tire deflection and the balance is struck between sidewall height and grip. I personally think that ultra thin sidewalls look bad and they have less ability to deflect due to the physical limit imposed by their smaller size. That being said a huge sidewall is not going to necessarily going to turn better because of the forces will not be as efficiently transfered to the wheel as with a moderate sidewall. Like I said it is a balance.

A practical example of this is modern racing tires. If tiny thin sidewalls were faster then every F1 car would be on wheels with rubber bands glued to them but they are not. Look at racing cars for the most efficient tire construction in terms of wheel size to sidewall/contact patch.

F1 rules state that the front tire must be between 305-355 mm wide with a maximum diameter of 660 mm. These are on 13" rims. The ratio of width to diameter is roughly 1 to 2 with the rim being roughly equal to the width. In short the tires are square. The sidewall height of the F1 tires is roughly equal in proportion to that of a "50" street tire.

So the most badass cars in the world are running on schweet 330/50/13s, how is that going to hang on the street?
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Old 12-04-2009, 07:13 AM   #10
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I agree, except for the F1 reference. They use such tall tires because the rules limit wheel diameter to 13". Race cars are actually a poor indicator of best practices, because important design aspects are dictated by the regulations.

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Old 12-04-2009, 07:22 AM   #11
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I think the key bit of info from the reference is that a 50 is where it is at. In my mind you start with a 50 then work it backwards to your wheel size, height diameter etc.
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Old 12-04-2009, 07:41 AM   #12
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I may be in the minority, but I'm really happy with my 17s. There's more than enough grip for the roads, the ride is stiff but not painful with the M030, the risk of bending a wheel on a pothole is relatively small, and tires are cheaper. I prefer a little narrower tire for minimizing tram-lining and somewhat increased feedback.

I'm not entirely happy with the style of the stock 2000S wheels, but I actually don't think 18s+ enhance the car's looks given the same wheel style, but that's subjective, of course.
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Old 12-04-2009, 07:48 AM   #13
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In this area, racing tells us Nothing about our "ideal" tire selection. That can only be determined buy comprehensive testing.

For F1 it's easy, build tires to match the maximum allowed height and width, to fit the maximum allowed wheel diameter. Whatever profile that works out to is purely coincidental.

Using your max. diameter and width numbers, the profile would be between a 46 and 54 "series", depending on tire width. Racing tires usually just use a diameter X width designation, such as 26"X13"-13.

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Old 12-04-2009, 07:50 AM   #14
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Yeah, I didn't think about that issue, my 18's do "tram-line", but I find it acceptable.
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Old 12-04-2009, 08:06 AM   #15
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blue2000s - I may be in the minority, but I'm really happy with my 17s. There's more than enough grip for the roads, the ride is stiff but not painful with the M030, the risk of bending a wheel on a pothole is relatively small, and tires are cheaper. I prefer a little narrower tire for minimizing tram-lining and somewhat increased feedback.

I'm not entirely happy with the style of the stock 2000S wheels, but I actually don't think 18s+ enhance the car's looks given the same wheel style, but that's subjective, of course.


I am going to have to agree with you on this one. I like the 17s for function and asthetics. Tires are cheaper, that is for sure. I just got a new set of wheels for the summer, and again, I went with 17s (though in the BoxS II design).

I love that everyone has their own opinion though. I enjoy seeing what other owners put on their cars in the pics.
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Old 12-04-2009, 08:21 AM   #16
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Wheel size is a compromise. You are balancing cost, weight, aesthetics and responsiveness to direction change.

Basically:

Cost: 17 is cheapest cost, 19 highest - 17 wins

Weight: 17 is lightest, 19 is heaviest - 17 wins

Aesthetics: 19 is prettiest 17 ugliest - 19 wins

Responsiveness: This really has to do with tire aspect ratios not wheel size. For the same overall tire height the 19 will be most responsive and the 17 least. However the 17 will have less unsprung weight which also contributes to responsive handling. Call this one a wash.

The 18" is probably the best compromise.

If you ignore aesthetics then 17" are best. They are lighter. The key is to not use the stock tire aspect ratios with the 17" wheels but instead use the same aspect as the OEM 18" tire. This will give the same responsiveness as the 18" and will lower the car by about 1/2". The combination of reduced unsprung weight and lower CG will result in a noticeable improvement in handling. The reduced unsprung weight will result in better acceleration and braking performance as well as a slightly smoother ride. The lower rolling diameter will result in improved acceleration at the expense of higher cruising RPM, poorer fuel economy and an inaccurate speedo.

The problem with the factory 17" wheels is that the are also narrower than the 18" or 19" so you can't mount as wide a tire.
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Old 12-04-2009, 09:01 AM   #17
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renzop, I agree completely.

To elaborate: I think the aspect ratio is actually a poor specification to use for comparison, as you mentioned, the true indicator is a tire's section height. I believe a section height close to 4" is a great high performance street car compromise.

OEM 17" section heights are around 4.4" front/ 4.6" rear, 18's = 3.7"/4.2" , and 19's = 3.2"/3.7"

Steve
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Old 12-04-2009, 10:00 AM   #18
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Quote:
Originally Posted by landrovered
I think the key bit of info from the reference is that a 50 is where it is at. In my mind you start with a 50 then work it backwards to your wheel size, height diameter etc.
Well except that the sidewall height isn't a set height, it is a percentage of tire width.

A 50 series tire has a sidewall which is 50% of the width of the tire. And tire width brings you back to the wheels because, as has already been mentioned, the smaller wheels do not generally come as wide.

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Old 12-04-2009, 10:17 AM   #19
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Quote:
Originally Posted by Lil bastard
Well except that the sidewall height isn't a set height, it is a percentage of tire width.

A 50 series tire has a sidewall which is 50% of the width of the tire. And tire width brings you back to the wheels because, as has already been mentioned, the smaller wheels do not generally come as wide.

I don't disagree with you and my comment was not meant to advocate smaller wheel sizes necessarily. Stock 17 OEM tire size is 205/50/17 front and 255/40/17 rear from what I understand. So if you stick with a 50 or a 40 for handling then you must increase diameter with a larger wheel, or you must choose a lower profile tire which will have different characteristics. Otherwise you are opening a can of worms by running larger or smaller diameter tires than stock. Trust me, I know all about the ramifications of tire size changes from my Land Rovers. We have to re-gear two diffs to maintain drivability with 35" tires.

For my purposes though, the stock boxster profile is fine. I am confident that I will get the best compromise of comfort and handling with these sized tires. The fallicy is that lower profile is better, that is what I was addressing.
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Old 12-04-2009, 12:49 PM   #20
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I believe 18's provide the best compromise on asthetics, ride quality, cost & performance.
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