I had those on because I was testing it with the new setup I put on the R40. While driving it, my friend could see why I said I had no need for 30mm rear. This car handles! I added more negative castor to the front of the car as well. I left a 2mm spacer in the rear end of the upper arm and put the rest up front. Toe in is -1 for the rear. Right height was about 5mm all around or 6mm rear and 5mm front. Also threw some of the front diff oil into the rear. Just about a big gob did the trick. Everything went great. Even for 40shore the car only slides if you throw try to pitch it sideways. For me it corners better, but that may have to do with the castor, not the tires.