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Hi Guys and or gals...
My used boxster came with 20"s and on my search before purchase, I saw plenty of cars running different wheel sizes
I was wondering, besides the higher cost of 20" tires, and the "looks" of the wheels on the car, are there any pros and cons of 20" wheels compared to 19's or 18"s??
 

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The only thing that I can see missing is sidewall height for pothole resistance, which may or may not be a consideration depending upon the condition of the roads that you drive on. Someone can correct me if I am wrong but I have never seen definitive evidence of noticeable performance gains related to sidewall height.

The main reason people get "dubs" is aesthetics - many think that more wheel and less tire looks better. My car came with 20's. Right now it has 18's with my winter tires. I like the look of both.

The other factor is Porsche - the wheel diameter generally goes up with the price. Base Box/Cay get 18, S get 19 and GTS get 20.
 

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+1 on the comment about pot holes.. I've got GTS 20in rims... and recently hit what turned out to be a road construction lip -- where the road's level changed by ???? from one level to the next. The "SLAM" was brutal -- and I immediately sensed for any pressure loss (happily none), but I'm sure the impact compressed the tire such that the rim contacted the bottom tread layer -- no "pneumatic" effect...
I think I escaped this incident, but multiple such hits might not fare so well. The 19in rims probably have just that much more pneumatic effect in reserve to handle a lot of pothole problems. --- Or just stay off roads under construction if possible.. ???
D
 

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The criteria for making a choice here are all so subjective.

A 20" wheel and tire have more "unsprung weight," standing alone a negative in a serious track car or race car.

On the other hand, a 20" tire has a stiffer sidewall, a positive attribute in a serious track or race car (simply put, less sidewall deflection and thus higher g-force potential).

A 19" tire may "communicate" slightly better in track-speed cornering as the wheel begins to slide under load. This is more or less important depending on your skill level. The price of that communication is diminished mechanical grip.

These are almost irrelevant factors in a moderately driven road car. In that context, you are mainly weighing looks against wheel damage issues.

I have a racing background and retain a strong high performance bias even for street driving. I am relatively careful around potholes and bumps. I like the look of my 20's and the feel on the street and track. I have had no issues with wheel damage. I would personally not change to a smaller size, especially 18s, where availability of tires is an issue. Also, 18s change the gear ratios ( not so with 19s, which have the same overall diameter as 20s). Again, this is so subjective and debatable.
 

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I ordered my BGTS came with 20" summer wheels, love the look and the openness of the barrel, makes them easy to keep clean, the ride is decent but definitely a little firm when compared to smaller diameter wheels. For winters I have 18" wheels, they are great for that purpose and allow for a better selection of winter rated tires. Interestingly the 18" wheels also provide for a quieter ride, the compliance offered by the taller sidewalls has a lot to do with this but so does the softer tread compound.

I think wheel size is mostly a personal choice, the look of the wheel and tire combination can be dramatically different between an 18" and 20" wheel, the ride is certainly different and only you can decide if the trade-offs for a given combination are going to work with your vehicle use.
 
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pros and cons of 20" vs 19" vs 18"

I ordered my 981BS with the 19s for several reasons. I like the look of the 19” BS wheel, but not the CS. I ordered the X73 fixed sport suspension which is stiff and felt the 19s might provide a little better ride. Finally, they came on the car whereas the 20s were an up charge. Had I not liked the 19” wheel (Cayman S), I would have paid the extra for the 20s and lived with the ride.

By the way, I’ve ruined tires by hitting potholes on two different cars. One was an 18” (high speed) and the other was 19” (low speed) so I’m not so sure it makes that much of a difference.


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Re: pros and cons of 20" vs 19" vs 18"

My experience is that the 20" wheels are notably stiffer than 19's - not objectionable to some but still notable. My understanding is that the 18" option, in Porsche's mind, is limited to winter tires. I would expect that if you get tires that are the spec diameter, the tall sidewall will reduce handling and feel. That said, I run 987 18" wheels and tires on the track, in part because I already had them. As dcharnet indicated, 987 spec tires are smaller diameter and indeed reduce gear ratios by a couple percent - that's not all bad on the track as you get a proportional boost in effective torque.
 

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I'm thinking of doing the same (20/18) for my 718 CS but really need to see what the "finished product" looks like with the 18" package before committing. Any chance you might share a pic of your BGTS with your winter setup? Thanks!
 

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Just to add some value to the conversation, it's useful to remember that weight savings in the wheel tire area (also brake rotors) overall are roughly double savings in reduced car weight - this based on rotating mass calculations. So if you save 2 lbs per wheel, it's like taking off 16 lbs from the car overall. Which is useful. The other issue with respect to rotating mass is that the closer the weight is to the center of the wheel, the faster it will accelerate - and the faster you can stop as well. As standard rims are heavier than tires, most often smaller wheels and tires with higher sidewalls will be lighter than larger wheels with low profile tires. Weigh them. Seriously.

Aside from overall weight, the distribution of that weight is also important. So, assuming that the overall diameter of any wheel/ tire combination stays constant (any increase in rim size is compensated for by a corresponding change in sidewall height) what really matters - assuming they weigh the same on a static basis - is how the weight distribution of the setups differ. Wheels for our Porsche autos are generally of very high quality and also very light so this isn't an issue the way it is for - say - a Cadillac Escalade with 22" wheels. In that case, the weight of the wheels is more than the original rims; AND the weight is moved outwards by virtue of the wheel's overall diameter; AND the tires are not much lighter than before as most folks go wider as they go with larger rims. The result can be a loss of performance (poorer acceleration, slower to stop) as well as a deterioration in gas mileage. Horsepower is needed to turn the larger rotating mass instead of a transfer into motion; and the reverse when braking.

So................spend some time looking at the weight of the larger rims, keeping in mind that most of that weight is always on the outside where you don't want to add weight. Look at tire weights too and try to understand if you are maintaining, reducing or increasing overall weight as well as rotating mass.

And yes - 20's look better. But not at the expense of performance.
 

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Dumbfounded in the lack of choices for the 18's. That said, in 5-8 years owners might lament the same thing when all the hi-perf tires are all 22" or 24". :eek:

And for tires/wheels, "unsprung weight" also translates into "lugging around the garage weight"; late 2017 I hurt my back the night I was swapping winter/summer tires.
 

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My first Cayman (08 CS) had 18's. The 4 subsequent are all 19's. I liked the looks of my Cayman R with 19s and lowered (X73) suspension. My 2014 Cayman had 19's and stock suspension and I thought the gap between fender and tire was a bit too much. When I ordered my 2016 Cayman Base I optioned 19's and X73......liked the looks and ride. My 2019 Cayman Base has 19's and PASM......again for handling and gap.
 

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One point that may be pertinant: The clearance between the calipers and the rim's inner barrel is less as you go to smaller wheel sizes. Even if the rims fit, the clearance between the caliper and the barrel may be so small that a pebble kicked up may catch between the caliper and rim and groove the rim.

If you go to bigger diameter rotors for a track upgrade, the 18" rims may not fit, at least with aftermarket rims. Obviously this is worse in the front if you have the red S calipers.

On my Cayman, as shown in my avatar, i was upgraded to 380mm Brembo GT brakes in the front and 345mm in the rear. The 19" Oz Ultraleggera rims on the car clear the caliper easily in the rear and I have grooved lightly the front rims due to pebbles. I cannot run 18" rims on that car.

V6
 

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My $.02. I get occasional bottoming in the rear with my 20's (15mm spacers) and X73. Very sensitive to bad road conditions - jarring in some cases such as the asphalt to cement transition you get with some bridges. A lot more tire choices in 19's which I use for the track. I would go with 19's. I know people who have traded out their 20's for 19's. I do like the look of the 20's over the 19's though. Hope this helps.
 

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How does the wheel height change the stiffest of the tire sidewall ? It doesn't. The ratio of the tire does. a 35 or 40 sidewall on a 18, 19, 20 or 21 is the same stiffest.
I put 2004 GT3 wheels with 255 & 285 x 18 Bridgestone RE71R on my Spyder for $3100 including shipping, mount, balance and nitro fill. Would agree the 20's look better but take the $2000 in savings.
 

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