I have a year 2000 996 with 18 inch wheels. Front is 7.5 " wide and rear is 10" wide. I also have the X74 suspension package.

I think wider wheels and lower profile tires will make the car handle better.
I want to stick with an 18 " wheel...For performance only...and just for the street.....I'm looking for the best size width wheels and the best size tires.

Any reccommendations?

 

You shouldn't really go wider than 225 in the front on the 7.5 " front...so that really limits you to about 285 on the rear to avoid magnifying the understeer you are probably getting (even with X74). If you had the 8" front and could go 235, that would probably give you better balance....but I would probably still stick with the 285 in the back even in that case to try and take out some of the understeer. If you wanted to go wider and didn't car about understeer, you can probably go up to a 295/30 on the rear in either case.

 

i have 8.5f and 11.5r. Loving the grip!

 

Go with GT3 sizes. They will fit perfectly on the NB 996 (I have them on my C2)

F 8.5 x 18 ET 45, R 11.0 x 18 ET 63 (tires 235 fronts/295 rears)

 

What wheel brand are you running?

What are your tire sizes?

 

With your wheel sizes at 7.5 front and 10. back stay with 225 front and 285 back. You are right with 18 in. wheel for best performance. Going to 19 in. is more of look than performance. If you want to go with bigger tires you need to replace your wheels to accommodate to wider tires. Keep in mind that will add weight too. Alignment and corner balance is a must.

 

Yes, GENERALLY thats true, except when your 18" wheels are more narrow and heavier than the comparable 19" wheels. If he has stock twists...he is pretty heavy, and he can get a lighter 19" wheel thats wider so he can have better grip. With that being said, he can also get a lighter 18" wheel as well....If he wants 18s, get a set of Carrera lightweights...Probably the lightest stock wheel Porsche made and he can get them fairly inexpensive if he doesnt mind finding a used set.

 

I stepped up a size to 19s last summer. They are coming off this summer and Im going back to 18s.

The main reason being is the ride quality. The 19s ride alot harsher than the 18s. I am sure tire brand is part of it but I think most of it is due the small side wall. I did not get any performance gain. If anything I got a loss. The car is much harder to drive (you dont get any forgiveness with that low of a profile)

The 18s are low profile anyway at 285/30 or 225/40.

This is the first sports car I have owned that didnt require a step up to improve performance. I love to add mods but IMO a wheel step up is not a good performance mod.

My car: 1999 C4 Cab

My .02

 

Funny, I got the EXACT opposite effect with the same car. I use 235/35/19 and 285/30/19 tires...with PSS9s, it rides BETTER than my stock 18s. I thought it did immediately but didnt say anything...my wife drove it and swore I bought some new suspension or something...she said its so much less bumpy than it was. If you used the 25 series rears, I can see how you get a more harsh ride. Also what wheels? That makes a difference as well. I have 19x8 et 57 (with 15mm spacers) and 19x11 et 67...

 

8.5 up front 12s in the back rides great lowered on pss9s

 

I can understand. You chose the same tire sizes and increased your rim diameter by an inch and you upgraded your tires. Your car is an inch higher.

If you keep the rim/tire size the same (which is the common practice) you have to have a lower profile.

How does your traction control work? Is your speedo accurate?

I guess you could do that and lower your car an inch and you would be back to stock height with bigger wheels or would the traction control and speedo be effected? Anyone care to comment on that?

Rim width has nothing to do with ride quality. What are your tire sizes?

 

[quote=glowone;1589669]I can understand. You chose the same tire sizes and increased your rim diameter by an inch and you upgraded your tires. Your car is an inch higher.

If you keep the rim/tire size the same (which is the common practice) you have to have a lower profile.

How does your traction control work? Is your speedo accurate?

I guess you could do that and lower your car an inch and you would be back to stock height with bigger wheels or would the traction control and speedo be effected? Anyone care to comment on that?

The fronts should be O.K...big difference is in the rears...

18 fronts (225/40/18) to his 19 (235/35/19) here are the differences:
Diameter (225/40/18) :25.08 in
Diameter (235/35/19) :25.47 in
Diameter Difference: 1.54%

Actual Speed (225/40/18) :60 mph
Speedometer (235/35/19):59.0 mph
Speedometer Difference: 1.555% too slow


18 rears (285/30/18) to his 19 (285/30/19) here are the differences:
Diameter (285/30/18) :24.73 in
Diameter (285/30/19) :25.73 in
Diameter Difference: 3.89% (anything > +/- 3% is considered out of range)

Actual Speed (285/30/18) :60 mph
Speedometer (285/30/19):57.6 mph
Speedometer Difference: 4.045% too slow (not sure how this is effected when the tire is on the rear?)

 

While there is certainly a limit, you should always get better handling from a lower profile +1, +2 tire/wheel change. The idea is that you increase the wheel diameter and reduce the height of the tire sidewall. This maintains the same overall diameter, but you have faster steering, braking and acceleration response since the flex in the tire is replaced with a rigid wheel. Now, you will also normally get a harsher ride. This can be mitigated by reducing weight. If you really want to have razor sharp handling, go up to a 19 or 20" set up.

 

I own a 04 C2 Cab and was told by Wheel experts that the best fit for my 597R HRE are P/O Rosso rims front 19x 8.5 .42, rear 19x11 .60. tires 235/35/19, 305/25/19. Any one running this combination and there comments.

 

I dont believe this is the case in all situations. The larger wheels and lower profile tires could potentially lead to handling characteristics that could make your car harder to drive fast.

I am not able to get technical on this but it will give me something to search the internet for later