Just see if the wheels chatter on the bench when they are turned. when they do, check servo horns to see if it's moving. If not, servo is not the issue. If they don't chatter on the bench, it's tire issue. Either tire themselves, ackermann or something else around it. Process of elimination dude. Good servo always helps in many ways but unnecessary investment should also be avoided unless you have lots of expendable funds . In the same token, if you don't have a servo equal to or better than Savox, you're not doing it right. So you should buy one regardless of this issue.