Rear tire size modification and the impact on car level and balance

If I go FROM the 265/35-18 rear tire TO a 285/30-18 rear tire on my 2000 996 Cab, would it be adviseable to switch FROM the 225/40-18 front tire TO a 245/35-18 up front in order to maintain the modest reduction in wheel/tire diameter? By the way, I have the OEM 18" sport classic II wheels. The point is, we all know that US model 996s sit a little higher up front in order to raise the front bumper to US required specs. If I switch to the slightly smaller rear wheel/tire combo (by my calcs, the 285 would be 0.6" less in diameter), the front bumper would stick up even more, right? However, switching to the 245/30 up front should even it back out. So, would a 245 width tire even fit on a 2000 996 up front without rubbing? Or would it adversely affect handling (oversteer now instead of understeer because of 'grippier' front? Is it preferable to maintain the 225/40 up front and figure that the rear tire change would be hardly noticeable? Put simply, does a 0.6" reduction in the rear really matter (and frankly, since the car only sits on half the wheel, I guess it's only 0.3")? Thanks for the look....and sorry for the wordiness.

Edward, Porsche moved to the 225/285 combo a while ago on the 996 anyway. You really won't introdcue any significant understeer. When I picked up a secondset of wheels and tires for the track I went with the 285 in the rear once my 265's needed replacing. If anything you could go to the 235 in front if you are worried.

Thanks Dell. It's not so much the understeer; there were a lot of threads that addressed that and I guess I could go to the 235s if it was too much of a problem. Beauty of the Pcar is that the rears run out faster so I'll have a chance to check out the 285s in back with the 225s in front first. If understeer is a problem, then your recommendation should fix that. However, I'm asking from more of an aesthetic perspective. Would the slightly smaller rears make the car look like the front bumper sits up even more? And, would it leave just a bunch of gaping space under the rear fender that looks awkward? (And Dell, don't say I should be running RoW M030 lowered suspension anyhow and it won't be a problem....that's the spring project. )

Here is a comparison of the 2 tires. 265 is the first line and 285 the second in every measurement. there is not nearly the significant difference you think you would see. Also, the variance of less than 3% is below the acceptable limit. 265/35R18 285/30R18 Section Width: 10.43 in 265 mm Section Width: 11.22 in 285 mm Rim Diameter: 18 in 457.2 mm Rim Diameter: 18 in 457.2 mm Rim Width Range: 9 - 10.5 in Rim Width Range: 10 - 11 in Overall Diameter: 25.30 in 642.62 mm Overall Diameter: 24.73 in 628.14 mm Sidewall Height: 3.65 in 92.71 mm Sidewall Height: 3.36 in 85.344 mm Radius: 12.65 in 321.31 mm Radius: 12.36 in 313.94 mm Circumference: 79.48 in 2018.7 mm Circumference: 77.69 in 1973.3 mm Revs per Mile: 822.1 Revs per Mile: 841.0 Actual Speed on 265: 60 mph 100 km/h Speedometer on 285: 61.3 mph 102. km/h Speedometer Difference: 2.298% too fast Diameter Difference:2.26%

THAT IS AWESOME!!!!!!!!!!!!! Thanks.

Very welcome