997 wheels-- 18s or 19s w/PASM

[mbs]

I just purchased a 2005 with PASM and 19 S Carrera wheels. I actually like the look of the stock 18s and prefer a less stiff ride. The Porsche website "The new PASM sports chassis is available as an option for Coupé models and only in conjunction with 19-inch wheels." Do I need to stick with the 19s or can I run stock 18s with out having steering or other issues. Thanks for any info-- sorry if this questions has already been asked, but I am a new owner.

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[996toomey]

You can run 18s.

[avh128996tt]

i have two sets of wheels 20" and 18" and believe me 18" wheels rides perfect . 20" looks awsome but the ride is very stiff for me . I love 18" ride for DD. With 18" wheels , you will be very happy , and you get slightly better gas mileage too.

[Minok]

To be clear, there are 2 types of PASM: The basic PASM and the PASM-Sport (aka SPASM). The SPASM gives you an even lower ride height.

Does your car have just PASM or SPASM?

If SPASM, there may be a reason beyond marketing, that SPASM (aka PASM Sport) is only available with 19" wheels.. but it may be due to other changes in the entire suspension beyond just the 19" wheels that come standard with it. The SPASM drivers could say for sure.

I know for my 997.2 (my2009) base, it comes (and I wanted it that way) with 18" wheels and I ordered it with PASM and there were no issues.

[p-cardriver]

I have a '07 997S with SPASM and I use 18s on the track and in winter. No issues.

[mrdonut]

Hi,
I'm not sure how much of a difference it'll make but I remember reading in "Excellence was expected" that they designed the 997 from the ground up to use 19" wheels.

There are some quotes here from another book that a Google Book Search (from "Porsche 911: Perfection by Design"):
"The decision to offer 19-inch wheels... forced engineers to design a new lighter and wider front and reader suspension"
"The 19-inch wheels forced power train engineers to rework gearboxes... shorter final drive gears"

http://books.google.com/books?id=ig5...wheels&f=false

Again, no idea how material the difference will be...

[Dadio]

Originally Posted by mrdonut

Hi,
I'm not sure how much of a difference it'll make but I remember reading in "Excellence was expected" that they designed the 997 from the ground up to use 19" wheels.

There are some quotes here from another book that a Google Book Search (from "Porsche 911: Perfection by Design"):
"The decision to offer 19-inch wheels... forced engineers to design a new lighter and wider front and reader suspension"
"The 19-inch wheels forced power train engineers to rework gearboxes... shorter final drive gears"

http://books.google.com/books?id=ig5...wheels&f=false

Again, no idea how material the difference will be...

Interesting comments in the book but confusing. I can understand the suspension tuning to deal with the heavier wheels and lower profile tires but the gearing changes don't make as much sense to me.
Given the fact that the rolling circumference of a 19" and 18" wheels would be nearly identical given the appropriate tires, why would the gearing need to be changed in any way ? Would love to hear an explanation from the gear heads in the crowd.

[Tech1_Mike]

Originally Posted by Dadio

Interesting comments in the book but confusing. I can understand the suspension tuning to deal with the heavier wheels and lower profile tires but the gearing changes don't make as much sense to me.
Given the fact that the rolling circumference of a 19" and 18" wheels would be nearly identical given the appropriate tires, why would the gearing need to be changed in any way ? Would love to hear an explanation from the gear heads in the crowd.

I recall, not so long ago, reading in this forum that putting 19s on a Porsche was tantamount to "heresy".
Aside from the obvious difference in cosmetics, there are but two reasons for Porsche to go up to 19 inch from 18 inch. First is the slight improvement in handling (at the expense of some ride comfort) in the shorter sidewall tire.
Second is the need for additional rotor/caliper clearance. My guess is that Porsche chose a larger wheel/tire combination for a combination of all three reasons: Cosmetics/Performance/braking.
The car business is fiercely competitive, even at the top. Constant innovation (and change) is an absolute requirement to stay in the game.

[Minok]

What I'm taking out of this is that the designers made some changes that allowed 19"s to run without so much of the ride issues that 19's used to produce years back; that is, the car now accommodates 19" wheels better. But, if the 18"s fit (and they pretty much do in all cases (other than PCCBs?) .. then there isn't any reason to worry about it: chose the ride and looks combination you prefer.

[mbs]

Thanks to all who replied, the information was very helpful. Does anyone know someone who want to sell OEM 18s for a 05 997?

[rvhpno80]

Originally Posted by mbs

Thanks to all who replied, the information was very helpful. Does anyone know someone who want to sell OEM 18s for a 05 997?

you can check ebay out, they have sales all the time on used wheels, or one of our sponsor on the side, wheel boutique is good and have great deals always, thats if you wanna go new.

[07speed]

That's about my only complaint with my car as far as a daily driver. The 19's are a harsh ride, especially on NY/NJ roads.