Maximum aspect ratio on Cayenne Turbo 20"

[cluck]

I have an opportunity to buy some Conti 4x4 contact tires for a decent price however, they are 275/45/R20's. Is 5mm in the sidewall going to make THAT big of a difference? No doubt it will throw off my MPG estimates but will it work?

[Loren]

Besides your speedometer this will also affect ride height and ABS performance.

[cluck]

Besides your speedometer this will also affect ride height and ABS performance.

Thanks Loren. This table is great. Speedo difference I can live with. Increased ride height I like. Affected ABS however....not sure I like decreased stopping distance.

[RFM]

And perhaps weird shift phenomenons (Tiptronic) because the final ratio is changed.

[cluck]

And perhaps weird shift phenomenons (Tiptronic) because the final ratio is changed.

Even more important. Really do NOT want to cause problems in the tranny. Looks like I'll just have to save my duckets for a full set of 18' rims and on/off road tires. Loren, just curious, how does your table compare 275/40/R20's vs. 255/55/R18's? I know they are both Porsche recommended options, but just wondering.

Thanks all.