ita ll depends on drivers skill, and what type of trails you want too do, as for too big, i definatly believe there is such a thing as too big, IMO anything that can stuff bigger than 40" tires is tooo big. my friend has a rock crawlwer jeep, d60 front and rear, with 40's and can do anything. as for too small well yea that exsits too but we wont go there :)