Mel,

I generally like to have the front tires just touch the track to help reduce some of the drag on the guide just a little bit.  It’s a fine balance.  If you have the tires riding up and all the pressure on the guide you might be slightly slower because of the friction/drag.

I agree with Russell’s statement – If it ain’t broke, don’t fix it.  Many a slot car racer has fallen victim to messing with their car too much and watching the performance go backwards.

Best of luck with it!

Marty