I am thinking about buying another set for track use, but I would like to know if 18's worth the difference. I made a search for combination of same brand of wheels and same brand of tires in different size 18 and 19, here is what I got

0.5'' difference in overall diameter for rear tires

wheels: VOLK racing TE37 tires: toyo R-888

18 inch:
FRONT:
tire: 245/40ZR18 93Y Overall diameter 25.7 in, weight: 26.0lb
wheel: 18x8.5 weight: 18.0lb
REAR:
tire: 315/30ZR18 98Y Overall diameter 25.5 in, weight: 30 lb
wheel: 18x11 weight: 20.0 lb

total:
front: 44.0lb rear 50.0lb

19 inch
FRONT:
tire: 235/35ZR19 Overall diameter 25.7 in, weight: 25.0 lb
wheel: 19x8.5 weight: 20.0lb
REAR:
tire: 295/30ZR19 Overall diameter 26.0 in, weight: 29.0lb
wheel: 19x11 weight: 22.0lb

total:
front: 45.0lb rear: 51.0lb

conclusion:
difference of 1.0 lb in rotational mass for front and rear. is that 1.0lb will make a difference and worth to go with 18

 

another compare between BBS in 18 and OZ in 19

18 inch:
FRONT:
tire: 245/40ZR18 93Y Overall diameter 25.7 in, weight: 26.0lb
wheel: BBS LM 18x8.5 weight: 22.0lb
REAR:
tire: 315/30ZR18 98Y Overall diameter 25.5 in, weight: 30 lb
wheel: BBS LM 18x11 weight: 24.0 lb

total:
front: 48.0lb rear 54.0lb

19 inch
FRONT:
tire: 235/35ZR19 Overall diameter 25.7 in, weight: 25.0 lb
wheel: Ultraleggera 19x8.5 weight: 21.6lb
REAR:
tire: 295/30ZR19 Overall diameter 26.0 in, weight: 29.0lb
wheel: Ultraleggera 19x11 weight: 24.0lb

total:
front: 46.6lb rear: 53.0lb

19 is lighter with lower profile tires in front

 

I would do the Volks. 18 or 19's it is up to. I have 18" Volks for the and 19" Sport Design for the track. Both work well IMO.

 

18's give you more options for tires

 

Stick with the 18's although Porsche claims the suspension is designed for 19's. I use 18's because my home track Sebring is very bumpy and 18's work better.

Also to keep the diameter correct for ABS to function properly you should use 305-35-18 for the rear. If you want to use the 315-30-18 rears then you need to use 255-35-18 for the front.

 

19" tires are becoming more common. You can get MPSC, PZero Corsa, Toyo 888, Hoosier R6.

Any others?

18's only clear advantage for tire selection is Slicks, other then that I think that it is personal preference.

 

Yes this is absolutely true. You can get plenty of 19's in R-Compound now.

 

thank you guys all for the replays, but what I wanted to know is:
if there is 2 sets one 18 and the other 19 same weight and same outer diameter, (performance wise) is there any advantage to go with one over the other? would lighter 19's perform better than 18? knowing that the rotational mass increase the moment of inertia, so more rubber and air or more metal ?

 

From what I understand most people go with 18's due to the fact there are better tire choices but I also understand more and more good tire choices are popping up for 19's. That being said I believe the 997.1 Cup cars came with 18's....food for thought

Jason

 

They don't make 19" slicks.

 

The one thing that I don't like about 18" tire choices is that they are not exactly the same size as the 19" wheel/tire size. I find the 18" wheels/tires sit a little smaller. This will effect real speed of the car at higher speeds.

All things being equal (weight and tire choices) I would pick 19" wheels and tires.

 

so if the conditions were the same... same overall diameter, same tires, same weight, same foot print, the only difference being the rim diameter 18 or 19... I would have to say the 19". The stiffer sidewall will be more responsive then the 18".

 

18" for sure

Lighter weight
Cheaper tires
more selection
better performance

 

get some 24inch TEs!


haha get the TEs brahhh!

 

I believe that this is a question that none of us can honestly answer. I choose 18's again because I got a great deal on a like new used set of CCW's PLUS my home track, Sebring is very bumpy and 18's seem to work better their. However one of my great track friends runs stock sized 19's (Toyo R888).

I spoke with Pat Long (Flying Lizards and Porsche Factory Driver) before and during this years Sebring race and Peter Litzenberger (Porsche Sport Driving School Instructor) on the phone about this subject. Both guys did not have a definate answer. Pat actually went to a Porsche Lizards engineer about this and told me to look him up at the Sebring race and he was told that the stock suspension was desgined around 19's and to try 19's. Litzenberger said there is really no firm test data but he has found out that on a wet track during PSDS 18's performed better.

I have a friend that tracks with me in his 07 997S. He uses stock rims on stock size tires in Toyo R88. I use 18's rims on Toyo R88's. I will ask him at our next track day if he would like to pit next to me and swap wheels for a session. That way he and I could tell the difference.