sidewall size on 20" wheels

[Cjallstar]

hey guys,
I know the OEM fitment for style 87's is 275/40/20 front and 315/35/20 rear. Anyone have experience running a bigger sidewall with the 87's or any other 20" set up; say 45-50 front and 40-45 rear? Wondering if it would cause any issues with the speedometer readings or anything else? I'd like to get a beefier sidewall as it will make me feel easier about driving around on 20"s on bad roads. Thanks in advance for the help.

[dkl]

Taller sidewalls on 20" defeats the purpose of having 20". Go with 19" if you want taller sidewalls. Since you're going staggered, I wouldn't mess around too much from the OEM sizes. Too much variations between the fronts and rears (in terms of the overall rolling diameters), will fry your transfer case!

[SuomiX]

The automatic transmission may(?) behave strangely if the diameter of tires is abnormal.
At least the 5-series(e39) steptronics has been told to have an unusual behavier with a too big or a too small tires.

- wrong change points
- turbine lockout problems (no locking at all)
- switching gears back and forth at certain speeds or the engine loads