I'm about to purchase new tires and not sure of what sizes to go with. I run a staggered setup right now 18" RPF1 9.5/10.5 +15 with discontinued RE-11 245/275 40 setup. Not interested in squaring things up; with my current suspension/sway bar settings, most understeer is gone I believe. I dont have the skill set to detect minor understeer, but definitely dont want to deal with snap oversteer. Currently, car turns when I want it to 95% of the time.

I'm looking at maybe 255/35/18 & 275/35/18 RE71Rs.

Or should I go bigger....265/35 and 285/30? Or 265/35 and 275/35 (lol, almost squared)

 

The re71r is not a fat tire and definitely runs on the average side...you will have a slight stretch with a 275/35 on the 10.5 wheel. They are very responsive in that config. I only run square setups, but if you are going to run a stagger then the 255/275 is what id go with.

 

I would do the 265/35 and 275/35 combo mentioned. Closer to square, but will be great for your wheels .

 

Does a squared setup mess with VDC? 265/275 is almost same tire height.

Right now my 245/275 setup there is about 1" height difference with no issues.

 

In normal use, there isn't an issue with 245/275. (265/275 even less chance of issue assuming F&R are both 35 aspect tires). Rule of thumb is staying within a F-R delta of ABOUT 3% difference (biased to rear based on front diameter). (OEM stagger is roughly 2.7% delta).

If your setup isn't triggering a wheel speed error (VDC/TCS input for ON) at ~3.65%, you're fine. Some cars may react to this amount of error, others less sensitive, not to worry.

Only places to worry about this is in a situation where the rear wheels spin (loss of inside wheel traction under acceleration out as an example) OR you run a rear tire that's smaller diameter than front (say, a 35 aspect vs a 40 aspect front), VDC will trigger and cut power sooner. Just be mindful of this on track or when pushing it hard.