CosmosMpower

I ended up just getting 305 rears

007DT

I came across this thread in search of needing new tires (old/used).
Currently I have 325 R 235 F. Long story on the tires and why I have this set-up. It understeers like a pig...

I want a better balance but do like the rears that size. So similar to the OP, but mine is an RS..

What set-up?
325 245
315 245
325 255

This car may see the track 1x per year (because race car). Mainly street and spirited mountain drives.
Also, suggestions on alignment set-up.

Auto_Werks 3.6

I find this so hard to believe, except that you're not the only person to say this.... If you're specifically talking about the firestone indy tire, its 0.3" wider tread width than a 305 RE71r. i have a hard time believing a normal average human driver can feel this change. Now the indy 500 front tires is also a little narrower than the 235 RE71r so the total relative rear tire increase is closer to 0.6". Firestone has a 245 that is 0.2" wider than the bridgestone and you have to give up 0.3" of diameter increase. All these specs are available on the tire rack website.

My car with RE71rs and 3/4 soft front bar and full stiff rear bar was undrivably loose on concrete, and its reasonably OK with 1/2 stiff in the rear. I have a hard time believing that you couldn't use the sway bars to correct 0.3" of rear tire tread gain.

RAudi Driver

Did you get cups and if so, can you post up a pic?

CosmosMpower

No, I had some like new RE11 fronts sitting around so I ended up buying a pair of new RE11 rears.

007DT

Why is this hard to believe... It's out of balance, size wise.. AND I feel that my fronts, which are older, are timed out. As I mentioned in my original statement the tires are questionable. Currently these are Mich PSS. I will be replacing them with Mich PS4c. The question is, what is the correct balance based on the largest size combo that can fit on a 997.1 RS.

Auto_Werks 3.6

I tried to be pretty clear, and provide data. I don't believe you can feel a 0.3" difference in actual measured tread. If the fronts are hosed, then yes, new rear tires will make it pushy. But that probably would have been the case with new rear tires branded as 305s. Did you max out the setup for the extra unwanted rear grip? Full soft front, full stiff rear, and play with adjusting pressures? I'd probably start with new tires for the front. It just doesn't compute that a 2.7% increase in rear tire could completely ruin the car.

HarmonyJim

I am likewise trying to fit the 997.2RS tires (245/325-19s) on my 997.1RS. Since theses sizes were decided upon for the 997.2RS, my guess is Porsche felt this was a properly sized set to keep the car's balance as best as is possible. I have been trying to find out if there are any concerns with this up-sizing - if the oem specs for alignment and ride height are retained. The confusion may have something to do with the fact that the offsets are slightly different, and the front wheels were 1/2" wider on the latter car. Add into the mix that the 997.1RS uses a 5mm spacer on the rear wheels, and you can understand where the confusion comes from. From my research, if the rear spacer is removed, it appears the 325 should fit - I hope with no rubbing issues. Of more concern is fitting the 245 front since the offsets are different between the two cars (53 vs 57) and the wheels are different widths (8.5" vs 9"). Somebody on this forum must have done this to an otherwise stock 997.1RS. Recently I have received a photo of a 997.1 running the desired combo, but I never get any information from the owner as to specs and modifications, so I cannot be sure it would work for us. Good luck on your search, and please post your results (as will I).

HASauto

For my 997.2 GT3...I ordered indy500 in 325 R and 245 F, they are sitting in my shop but have no installed them yet. At eye view they are barely any wider then my current pirelli 305/235 however the diameter seemed significantly bigger on the 325 then the 245. Now I am rather confused since this is the oem size for the RS.2. Is the dimameter really that diffent or is it just with the Indy 500 tires?
thxs

HarmonyJim

Bump

gt2-josh

Why are we still discussing this topic? Lots of bright folks have given serious reasons why this is foolish. The response being it's cheap and looks cool. I'd say if those are your reasons you got problems with aesthetics physics money and it appears you're bored. Please stop. Nobody here is going to prevent you from doing something stupid. So go for it and put us out of your misery. Thanks.

HarmonyJim

Schmuck

HarmonyJim

Hey Josh, this topic has merit in that the 997.2 RS used this EXACT size combo. Go tell the Porsche engineers they are foolish - I am sure you are much smarter.
Those of us with 997.1 cars who would like to run the same sizes would like to know if they actually will fit considering all the variables having to do with wheel width and offsets. Go **** off if you are bored with this and scroll on.

gt2-josh

That could have been the worst logic ever. Of course it fits. It's also absurd. I bet you can put a gun to you head and blow it off. But instead of debating it here please test it out and report back. Thanks!

HarmonyJim

Spare me your condescending bull****. "Of course it fits"...I am glad to hear you are so certain of this. I was under the impression these forums were to share information, not to listen to ******** like yourself play forum ****. As to "that could have been the worst logic ever", what the hell are you referring to? Do you even understand the concept of logic? Sorry I have upset your sensitive bitch-*** sensibilities. Like I said earlier, go **** off and scroll on by if you are bored. There are thousands of other threads. I can do just fine not hearing from ignorant, unhelpful trolls like yourself. It appears you need a hug and a Midol. Those cramps can be tough. Time to go to your safe space.