It depends how low you want to go, I put some 30mm kingsprings on my 33 a few weeks ago and It didnt seem to affect the rear camber a whole lot, so I think this is a safe height, however if you want to lower it more than this you will get quite alot of neg camber in the rear, which will effect tyre wear and driveability. Then maybe a camber kit maybe necessary, the choice is yours.