I think you are better off with a 10th car. Obviously something supported by the local market is best, and a name brand will have more long-term value. Avoid the RTRs with powerful motors - a silvercan is plenty for first-time driver. Tamiya DT-02 series comes to mind, and if you buy kits then you could make building and maintaining the car part of the project...
18th don't really work outside unless the surface is immaculate; electrics are a bit of a nuisance at times - even if you find one that takes a 10th servo, you are still running with non-standard batteries and motors; tyres can be a nuisance too, especially if there isn't the local availability.
I own a couple of Mini Inferno STs and they are fun in the garden with the standard motor and fairly reliable, but I'm not sure they would be a very satisfying racer, they don't really steer and the drivetrain slips away most of the power.
|