is it rubbing on both sides ? can you locate where the rubbing is in terms of the front or rear part of the tire ? if the rubbing is happening at the center of the tire, camber should fix it , if its happening more towards the front or rear of the tire, a little toe adjustment could do the trick.

 

The rubbing on the front is on the fender liner "bump out" it's on the vertical part of the liner just behind the light and below the side marker. The rear is only the fender lip.

 

I am lost here. My current track tires are bald so I was looking at 245 40 18 front and 305 35 18 rear. I am AWD. Why doesn't this work? What's going to happen if you run this setup?

 

the 305's will be to short of tire and exceed the factory the tolerances for front to rear heights. However, AWD damage is may or may not occur as there's no consensus on the facts. get 315 or stay 295

 

Better images of my set up. No rubbing with my GT2 setup.

 

Your wheel specs and tire sizes sound good.

 

That's incorrect. The 305/35/18 will actually be almost 1" taller than the 315/30. No one makes a street 305/30/18 tire. The 245/40/18 and 305/35/18 is a fantastic GT2/3 set up but will not work with AWD since the rear is so much taller than the front. The NT01 305/35/18 runs very wide and sits square on a 12 wheel. I have run it back to back with the 315/30/18 NT01 and the 305 provides better performance due to a larger contact patch, stiffer sidewall, and a higher load rating.

 

Because the rear tire is almost 1" taller than the front and rotating slower than the front. I order for the viscous coupler to transfer torque to the front, you need to have the rear wheels rotate faster than the front. If the fronts are rotating faster than the rears than they are basically providing driveline drag. No one has proven what amount of delta front to rear will cause any VC damage and you could debate it till the cows come home. Hence the widely used 3%. From a performance standpoint though, 3% larger rear than front is NOT the same as 3% larger front than rear.

 

dang, hound.. you sure make this stuff simple to understand!..so would you go with 245/40/18 and 305/35/18 over the time honored 235/40 X 315/30 running rwd on 9X12's? and why? contact patch.. is it that simple?

i like that i can try that setup now...

 

Yes, it is that simple and that is what I recommend, fwiw. I have tracked the 235/40/18 and 315/30/18 NT01 combo for several years before switching to the 245/40/18 and 305/35/18 NT01 combo at the urging of the gentleman who set up my car. I find the new set up superior and I'm about to mount up my third set. The 305/35/18 is over 1" taller than the 315 and runs very wide. Due to the larger diameter the contact patch is bigger than on the 315. The 305/35 also has a higher load rating and stiffer sidewall and as a result the 305 rolls over much less than the 315. I actually run about 4 psi less on the 305 which further increases the contact patch. It's a win win all the way around. If you are RWD, it's a no brainer. On a side note, I have run both combos on 18x9 and 18x12 wheels. If you want I can post some pics of wow the tires fit on the wheels. They fit very square on the wheel.

 

i like the idea of more rake, rear to front also..i'm going to try that next time as i'll need to swap all four by then. but it seems it's really the 305 on the rear that makes for "most" of the difference? i can't imagine a better or more flush setup than i have now.. except for more rake. an inch taller rear, i can see that. i'm running a cpl psi less now with the rwd ( 38 cold from 40 ). what psi do you recommend? i have been 36/40 with great success on ps2's. cpl pics would be great. i dont want the stance to change much, again, except for the rear being taller. thx for the info.

 

With the 245/40 & 305/35 I run 33/34psi hot at the track. I start at 27/28 cold and and bleed down to maintain 33/34 at the end of a session. For street use I run 34/37. My alignment is -2.9F and -2.25R. Ride height is 102/125mm. 3245lbs with fuel. You will have to realign the car once you have your rake set. Here are some pics...

 

nice. my ride height is similar.. as is psi. i will try those sizes next for sure. thx!

 

A better image of my set up. 235 and 315's


Jim