I use Kumhos too. Great in the dry, not bad but certainly not a Michelin in the rain. I know, as I have 2 E34s one has new Pilot Sport 3s on one and Kumhos (here in Oz they are 'ECSTA Sport SPT' 225x50x16) on the other.

You can buy 55 series if you want comfort, but they are ever so slightly larger and may just touch a front guard at compression as it does on mine. Not dangerously, but IMHO it'd be best to plan rolling the front guards if you get 55s!

I bought ZIEX 225s for my e28 once. Found them terrible in comparison to the Dunlop Sports (SP2000 and SP3000; SP2000 are factory e36 M3 fit). I reckon the Kumhos are as good as those, but the SP2000 would definitely beat them in the rain.

Note: 50s have a slightly smaller rolling diameter than stock 15s with 225x60 15s. 55s are slightly larger. If you're car is lowered, fitting 50s will really 'lock it down and put it on rails', hint: If you add fat swaybars you'll really need taller seat bolsters as you won't slip to the sides. The cornering G-forces will be doubled!