i use soap and water...witha plastic scourer (as in a washing up sponge with some scratchy plastic on the back) that gets most of the crap off the side wall...I got some stuff from a company called Autoproud, Tyre and whitewall dresser. you have to clean the black wall and then the white wall separatly but it works pretty good...if you do scuff the white wall though there ain't much you can do!
You might want to do a "Search" as this has been covered many, many times on here. On my cars I use Simple Green and and a ScotchBrite pad.
The best I've found so far is Wesley's Bleech-White....spray dry tires, scrub, rinse! Works on ALL tires...I use it in blackwalls, too! Get it a WallyWorld, AutoZone, Advance, etc.......
The Jalopy Journal
