We wrapped some wide elastic bands on each of the back wheels - works perfectly :D
We paid £45 for this in May. It’s a great little ride on toy for kids - battery lasts a good while too. Bit of a faff to put together but good value. They only use it on paving - the mod above sounds very sensible for grass use.
I hear these are shooting up in value now they've stopped making them! ;)
Thanks OP, purchased for my nephew :)
My unnoficial mod for hilly or otherwise slippy gardens. (Old bike tyre). Without it the car was barely useable as it is 1 wheel drive. Goes anywhere now!