The tc4 track width is way too small: 188mm in front and 185.5mm in the rear !!! Use Xray #305380 ($5.99)shims to get it as close as possible to 190mm, and you will shave three seconds Off your laptimes... These shims are expensive, but Work like no other.... You'll need four to five sets of shims($24 to $30) to make it work... I believe tamiya makes these shims too, but they are hard to find...