thesubaruguru

Have 09 G37x, 31k with evenly worn RSAs on OE 17x7.5.
Even at 36psi turn-in feels heavy on center and non-linear. Would ADVAN S4 or Kumho ASX reduce that centerline understeer?

Am thinking about keeping OE rims for winter set with maybe Kumho KH16 or similar. So the question of running staggered with ATTESA looms again!

I've read the threads, and am almost convinced that it's worth a try.
(I've 20+ years experience setting up HUNDREDS of Subaru AWDs, knowing full well that the 60/40 weight distribution simply requires that FRONT tires be equal or SLIGHTLY taller than rears to protect transfer case. This isn't rocket science. If you run different brands just ensure taller ones are up front where the extra weight squashes them down to equal rolling radii.)

But ATTESA is more sophisticated? Electronically, perhaps. But if it's truly RWD until 5% slip then actually it's MORE tolerant than a fully-engaged AWD like Subie's. Nevertheless I don't want to screw it up.

I'm thinking that lighter weight and 18" up front will help turn-in feel, so the 225/50 x18 seems attractive up front. OE is 7.5". The ASA AR1 18x8 are lighter, a good deal, and not too wide for 225/50.

The REAR choice is more problematic. 225 seems indeed quite skinny back there, so I'm tempted by the 245/45x18 OE idea. Nissan uses 8.5" back there in staggered setup. So first question is whether to use same 8" ASA rim in rear, or take advantage of their 18x9? The latter seems to make perfect sense.

EXCEPT: Rolling radius of 245/45 18 is 1/2-1% smaller than 225/50 18 for most tire brands (I'm specifically looking at RE050A for their lightness and dry grip). If I keep same 8" wheels in rear they'll squeeze the 245/45 back up to equalize the front's circumference....

OTOH: The increased weight on the front of the G37X will squash the narrower 225s down anyway...as will the 8" rim instead of 7.5, so they will approach nearly identical rolling radii....

I ASSUME that 8" up front will keep the 225/50 18 "squarer" for crisper turn-in, but will the slightly wider wheel increase centerline understeer?

I ASSUME that 9" in rear will help put that 245/45's traction down.

I understand that some of you will suggest that using the identical 8" wide wheels is "better" for ATTESA, as of course would follow a knee-jerk similar prohibition against different width but identical height tires, but I hope we're past that. Correct me if I'm wrong. (I've watched Subie techs with tape measures ensuring that circumeferences are within 1/4" when customers complain about AWD chatter, when all they needed was an ATF change and rotation to taller-up-front. But how else to sell 4 unneeded new
tires?)

If the ASA 8" Front 9" Rear setup sounds good I'll go with it; if you REALLY think I'd be better off with 8" all around because 245/45 18 don't need 9" then I might await the upcoming Bremmer BR05 if they're also under 24 lbs. That then begs the question of just getting used OE, which I suspect are heavier? I'd only do that if the OE 7.5"+8.5" width duo is somehow better than ASA et al 8"/9".

So the short term cheap experimental solution is to trash these worn 17" RSAs and chase strong used RE050A 225/50 and 245/45 on the ASA RSA staggered 8" and 9". Agreement? Thoughts?

Thanks a bunch!
Ern