a rear anti-roll bar aids in reducing body roll and weight transfer while cornering...it won't stiffen the chassis like a tie bar...the thicker you go on the rear, the more oversteer your going to get...this is good up to a point..if you keep going thicker and thicker rear anti-roll bar the more squirrly your rear end will be....the FF design of the Civic, Integra, etc. tends to cause more oversteer...the cure for this is a good sized rear anti-roll bar, say 22mm and 19mm or less front anti-roll bar will be good...depending what car you have, some have front and rear anti-roll bars...like I said before, Tie bars just aid in responsiveness of your car