Mark
Do I take it you're using Gibson wheels for this? If so be very careful when soldering shorting wires to the back of the tyres as the Gibson centres distort very, very quickly with any form of heat near them. I know, heat...plastic...duh, but the speed of distortion can be quite amazing! Done it, been there, got the T-shirt. I ended up using a cold wet tissue as a heat sink around the join. The only reason I didn't in the first place was because I was originally using Sharman Wheels and their nylon centres were very resilient to heat.
Good luck
Tony