can i get away with a narrower tire?

[usdmej]

whats up fellas, i originally purchased this car second hand. i don't know how wide the rear wheels are, they are Work Brombachers, which come in a myriad of sizes.

the tire on it now is a 305-25-19

i need to change them out soon, i want to get a taller tire with more sidewall, also i was wondering if i could make it narrower too, a 295 or maybe even a 285 section tire?

here are some pics, tell me what you guys think i can get away with

[Lee Quave]

Sure you can just make sure the diameter stays close to that of the approved tire sizes. If you track the car you may want to look into the effect of changing the width of the rears in relation to the width of the front tires. There is a lot of information on this site and you can also search the forums on rennlist.com.

BTW I like the wheels.

Good luck.

[KevinMac]

whats up fellas, i originally purchased this car second hand. i don't know how wide the rear wheels are, they are Work Brombachers, which come in a myriad of sizes.

the tire on it now is a 305-25-19

i need to change them out soon, i want to get a taller tire with more sidewall, also i was wondering if i could make it narrower too, a 295 or maybe even a 285 section tire?

here are some pics, tell me what you guys think i can get away with

It is my understanding that 996 prior to 2002 were not recommended to have over 18 inch wheels. The 18 inch package had the rear tire size of 265/35/18.

So if you really want to keep with the design of the car, you may want to go back to an 18. This will give you a higher sidewall, the height of the tire wil be about the same. By using the exisitng 19 inch wheel you have now, and going to a taller sidewall, the handling will change. The 19 you have on there now, pretty much map to the same circumfrance and tread width as the optional 18 recommended by Porsche.

If you narrow the footprint, you may have some rear end moving out from under you. These cars have rear engines, and from 99 on up Porsche has overcome the death rear end in earlier Porsche cars. One can only summize that the footprint used in these cars is one of the engineering design to improve the handling capability and over come the death rear end.

The 18 inch has a 3.7 inch sidewall and the current 305 you have a 3 inch side wall but the overall circumframce and diameter and foot print pretty much match the 18 inch wheel and tire size. So in a nut shell leave it as is!

BTW take a look at the 19 inch wheel post. The guy who changed from 18 to 19 says the handling is better with the 18's.

Edited May 28, 2008 by KevinMac

[Loren]

It is my understanding that 996 prior to 2002 were not recommended to have over 18 inch wheels.

My model year 1999 Carrerra came with 18" wheels. There was no restriction mentioned in any TSB.

Carrera's before MY02 were not recommended to have the X74 suspension upgrade because the chassis was not strengthened like the MY02 and newer cars. Perhaps that is what you were thinking of.

[KevinMac]

It is my understanding that 996 prior to 2002 were not recommended to have over 18 inch wheels.

My model year 1999 Carrerra came with 18" wheels. There was no restriction mentioned in any TSB.

Carrera's before MY02 were not recommended to have the X74 suspension upgrade because the chassis was not strengthened like the MY02 and newer cars. Perhaps that is what you were thinking of.

Loren, actually two Porsche dealerships down here said Porsche does not recommend anything past 18" wheels prior to 02. They may have been refering to the X74 suspension or the lower sidewall but never elaborated. My 2000 also came with 18 inch wheels, which was an option at the time.

Edited May 29, 2008 by KevinMac

[Loren]

I am not recommending anything beyond 18" wheels - I am saying 18" wheels are ok on MY99-MY05 cars.

[jam996]

I wish I knew a bit more about this before I purchased my wheels 19" 8.5/10.5

and the tires size everyone kept recommending was 275/30 rear and 235/30 front.

but the wheel comes out of the tire as if tire is not wide enough.. Isn't that dangerous??

the installer told me its ok. Ive never seen that before and dont want to get into an accident to find out.

Im a bit confused about what to do, should I get wider tire or if its safe just drive it for the summer and switch back to 18" for next summer.

please let me know if it is safe to take out my Porcha.

btw I have MY99 C2 coupe.

thanks

Edited June 1, 2008 by jam996

[jam996]

anyone know if its safe or not.

[usdmej]

It is my understanding that 996 prior to 2002 were not recommended to have over 18 inch wheels.

here is my stance on the situation

i think 19inch wheels and tires were never listed as a recommended size by porsche, but porsche has never oficially said that they DONT recommend putting on 19" wheels/tires. think about it, 10+ years ago who was thinking about 19inch wheels? not that many people so porsche never R+D the possibilities.

this car is mainly a daily driver, i'm well aware of matching the overall rolling diameter if i decide to change sizes, actually the 305-25-19 on there now has a smaller rolling diameter effectively lowering my gearing. not good for cruising at all.

my original question is this. Looking at the width of my rear wheel, would a narrower tire fit?

[KevinMac]

It is my understanding that 996 prior to 2002 were not recommended to have over 18 inch wheels.

here is my stance on the situation

i think 19inch wheels and tires were never listed as a recommended size by porsche, but porsche has never oficially said that they DONT recommend putting on 19" wheels/tires. think about it, 10+ years ago who was thinking about 19inch wheels? not that many people so porsche never R+D the possibilities.

this car is mainly a daily driver, i'm well aware of matching the overall rolling diameter if i decide to change sizes, actually the 305-25-19 on there now has a smaller rolling diameter effectively lowering my gearing. not good for cruising at all.

my original question is this. Looking at the width of my rear wheel, would a narrower tire fit?

10 years ago 19's were around on many cars in this performance range. There has to be a reason why the 18's were an option and not 19's.

Here is an explaination from European Car as it relates to 996 wheel size! In essence Porsche has made a statement.

"Consulted Michelin and Porsche engineers along with some seasoned Porsche racers about this. Porsche's engineers did not find our problem surprising and said, "All the fuel and chassis control systems on the 996 Turbo are built and tested around the wheel and tire size and their corresponding rolling radius. Altering the standard size not only has adverse effects on the performance and handling but most likely could end in damaged drivetrain parts such as a broken front differential or viscous clutch damage (not a warranty matter). The weight of the wheels and tires is not a major factor." This just goes to show how dialed in Porsche's cars are out of the box."