Thought the answer might be a bit late, if the problem still persits, what exactly do you mean you changed wheels?
You went into your 3d software like 3ds Max or Blender, took and existing car and then changed what, the rubber compound, the rims? And you made sure to also replace them in the correct helper dummies, so WHEEL_LF, WHEEL_LR, WHEEL_RF and WHEEL_RR and the same for rim and rim blur and also made sure to include the new textures while importing it in ksEditor?