In the year XII – Xray XII 1/12th scale
Track test
For a first test of the Xray XII we headed to a small indoor track near Hamburg/Germany that offers a high grip but rather bumpy carpet surface. Not the best place for a new car but with the racing season still in hibernation it was the only possibility to test the new car.
After the first couple of laps we noticed that we had to raise the height of the body which was no problem on the front but on the rear of the chassis. Since we already used the topmost position of the body posts we had to add some spacers underneath them to properly raise the body. Maybe its just a problem with the BlackArt R8 but since did not try a different body, we don’t know!
After lifting the Audi shell we went back to the track finding that the damping of the friction damper was a bit on the heavy side for such a bumpy track. What seemed ok on the workbench proofed to be quite a handful on the track. The rear of the car was a bit unpredictable as it stepped out in more than one corner. Back on our pit table we released the damper plates from the sticky Corally damper syrup and added a fair amount of Xray differential grease. The result was a much freer rear end. While working on the back of the car we fitted a milder Speed Passion 9.5T Ultra Sportsman Series motor to replace the GM-Racing 5.5T power mill that proved to be much too powerful for track and driver! With a rollout of around 48.7mm the XII was a bit on the slow side so for the next time out we make sure we have large enough pinions on board to gear in the 50 to 52mm range!
Back on the track the XII seemed transformed. With pink Xceed tyres on the rear and purple Xceed tyres up front the XII had a massive amount of steering but was still very controllable after we dialed out some steering throw.
The next thing to take care of was the to get rid of a bit of steering on the turn in of the slow and medium corners. At first, we tried to increase the caster angle by spacing the upper arms of the front suspension to the rear by about half a Millimeter but that did not cure the problem. Instead we went back to the factory setting and decreased the angle of the reactive caster from 5° to 2.5° by using the offset insert mounted with the whole in the low position. To receive (nearly) the same overall caster we had to space the upper arms 2+1mm on the front of the arm and 0.5mm on the rear making 7.5° in total (compared to the previous 7°). This change made a huge difference. The car was easier to drive but still had enough bite for a quick corner entry. The last tiny change we did was to increase the preload of the shock to raise the middle ride height a bit as it seemed the chassis bottomed out on one or the other bump.
