There was a guy at the track in a 997S running 295/30R18 tires in the rear and 235/40R18 in the front. According to many opinions/assumptions/suggestions, that tire combo shouldn't work as they're too close in diameter (rears are actually slightly smaller than fronts).

Any experience? Research shows that R888 are the only option if I want to maintain a semblance on proper diameter ratios. What are the potential repercussions of running the above combination?

Thanks in advance, info here always helpful.

Adam

 

I have run that combination, but am currently running 245/35/18 and 315/30/18. R888 are the tires available in the 295/35/18

 

Since the OEM 19 inch tires are:

235/35/19 F
295/30/19 R

In 18 inches it should be:

235/40/18 F
295/35/18 R

Most tire manufacturers show their diameters, if you can't get the OEM diameter you should at least try to keep close to it.

 

...no it should be 245-40-18 and 305-35-18....I've posted this about 1000 times.

But since you all don't believe me or trust me I am done trying to help out.

 

I agree that those are the ideal sizes Mike, but there is a limited number of manufactures make a tire in the size. Please don't stop with your valuable help.

 

Mike, is there any specific reason for going 1 size wider in both front and rear?

 

mdrums, I have referenced many of your posts on multiple occasions and your help is always welcomed. The problem I'm having is that I'm trying to conserve funds and run on my 10" rear OEM 18" wheels. I don't think that the 305 will fit properly.

The other concern, that has already been addressed is the limited if not exclusive availability of tires (R888).

I'm just looking for an alternative tire, if they exist. If not, I might just look at some slick tires.

 

stock 10" wide real wheel is a PITA. I got hoosiers a6 in 245/295 on `em and they are quite too small. rear is 25.3" and front 24.7"

essentially that is why I just got CCW in 9" front 12" rear as there is almost nothing that has correct sizes for stock 8" and 10" wheels.

look at toyo RA1 btw.

 

Atr911 just use the stock Carrera 18" sizes. Maybe Michelin Sport Cups or Toyo RA1 R888 come in the stock Porsche sizes for 10" wide rears. I did not know you were using small width wheels so that is why I was suggesting the other sizes which still optimal. Just keep the front to rear ratio diameter wellwith in 4% from the way it has been explained to me so that PSM and abs don't freak out

 

997 is not the 996/993.

Therefore, you should keep the overall diameter (OD) within 99%/103% range of:

25.48" (front)

25.97" (rear)


Few popular sizes:


Front:

235-40-18 = 25.40" (99.7%)
245-40-18 = 25.72" (100.7%)
245-35-19 = 25.75" (101.1%)
235-30-20 = 25.55" (100.1%)
245-30-20 = 25.79" (101.2%)


Rear:

295-35-18 = 26.13" (100.6%)
315-35-18 = 26.68" (102.7%)
305-30-19 = 26.20" (100.9%)
325-30-19 = 26.68" (102.7%)
305-25-20 = 26.00" (100.1%)
325-25-20 = 26.40" (101.7%)



i WOULD NOT run on a 997:

235-35-18 = 24.48" (96.1%)
295-30-18 = 24.97" (96.1%)
305-30-18 = 25.20" (97.1%)

It's just not the right sizes for the 997, period. Not to mention that would look ugly...

 

Lets see some pics big guy...