CosmosMpower

Thinking about trying some Pirelli DH slicks in 245/645/18 but undecided on rear size. I know most people run a 305 rear mostly because the 315 rear sidewall is usually too short for tires like the NT01.

If you could choose between 305/680/18 or 315/680/18 to go with the 245/645/18 on a 18x9 front wheel and 18x12 rear wheel which rear size would you choose and why?

Stock suspension 07 non RS GT3 plan to run around -3 front camber.

audipwr1

That is a lot of load on your suspension - should start timing out parts (control arms, kingpin bolt, etc) if you run that kinda grip IMO

CosmosMpower

I wouldn't think it's much more load than Hoosier R6/R7, it's the hard compound slick. Are suspension parts really going to start failing?

Back on topic, which rear size is more ideal?

AudiOn19s

the 305 vs. 315 nitto on 997 cars is because the aspect ratio's are different on the 305 and better suited to the 997 ABS

The slicks in question you are asking about are both the same height at 680 (~26.9).

F1CrazyDriver

As for timing out, eh. Unless you are only driving on fresh slicks(no more then 4 heat cycles from new) (not) driving at a pro level & pumping out qualy laps only- you will be fine. Equal to Hoho's / nt01. Suspension parts will not time out. I have ran them on my Turbo for many, many years. 0 problems. First hand experience.

As for sizes you want.

245/645/18
305/680/18

The 315's are extremely wide. Unless you get custom wheels, you will have a hard time fitting 315's. Perfect balance comes with the 305's. The 680 sidewall really helps for trail breaking as well.

P.s. You will have to take your car to a shop that is familiar w/ GT3's and Pirelli slicks. Each slick tire has its optimal alignment to extract the most out of the tires.

I'm going to list my foregelines for sale soon & they come with Pirelli's,

CosmosMpower

Right which is why I'm asking which one to run since the aspect ratio are the same. Is 245/305 better or 245/315 from a width/balance/wear standpoint.

CosmosMpower

Thanks! Are 18X12 wide enough for 315? I'm running the 315/30/18 NT01 right now and they seem to be wide enough to support that tire. My car is actually a bit tail happy. I'm worried if I go down to a 305 it will be even looser. I do need to get my car aligned though, could be a toe problem.

zweebach

I run the 315/680 Pirelli on the rear of my car, granted it's the wider body and wheel offset comes into play, but I use a 12.5" wide wheel. They'll work on a 12" wide wheel just fine. I think you'll mainly just need to make sure it fits in the fender without rubbing with your particular setup. I'm in the Dallas area if you need more help. I'm about to discard some 315/675 Pirelli's (675 has gone to 680), if you want a free tire to try out for fit.

rs4_saloon

I've been running DH's as well on a NB .2 GT3 and I run 245/645/18 up front and 325/660/18 in the rear. I run a fairly aggressive alignment so I can get proper grip out of those tires and the yoko A005 (more than -3 upfront...upwards of -4 and -2.7 in the rear). I'm also running 850/1100 spring setup with revalved bilsteins.

I was under the impression that the X/680/18 tires were gonna be too tall on NB GT3?

F1CrazyDriver

I run Pirellis 305/680 on my .1 NB. Fit perfect. I have 18x12's with WB .2 RS off set, however i do drive slow so i do not see a need for wider rears. It all comes down to driving style/speed.

I'll see if i can get pictures.

CRex

The timeout is real. My thrust arm bushings went from okay to completely shot after about 20 track hours after going from R6's to slicks.

You're safer going with slightly narrower sizes. Pirelli slicks have a rather square sidewall profile and fill the wheel arches more than the comparable size OEM street tire. That was the case when I ran 245-650-19 and 305-690-19 on my WB .2RS

CosmosMpower

Thanks for the info. I might order the 305 and take you up on your offer to see if the 315's will clear my car. Do you happen to know the section width of the 315 tire? Maybe I can compare to the 315 NT01's on my car now and see if it will fit.

CosmosMpower

I thought for the rear you have to use a tall tire. I know the 305/645/18 were too short similar to running the 315/30/18 NT01 vs the 305/35/18 which are the correct height.

rs4_saloon

325 rears on a NB

rs4_saloon

The 325/660 combo has been working well for me with no issues of the computer throwing abs/sc/tc issues. I've gone through two sets and I'm on my third now.