@tmarkson
First of all - thanks for such a detailed reply, I was worried that no one would ever reply 
What size are we talking about? Do you want to ride this larger robot? Any requirements for runtime and terrain capabilities?
Yes I would like to build a rideable one. I think the runtime should be at least 30 minutes for it to be any fun. And it should be able to run on any hard surface - I don't think I will ride it in any terrain except maybe grass.
I haven't tried to simulate the robot yet, but I have done some basic calculations with a total mass of 90kg and a wheel radius of 8cm. You can see them in the attached pdf.
I haven't done any drawings of the robot yet, but I will try to do it and then - with your help hopefully - calculate the specs of the robot 
I won't do it this week, as I'm very bussy at school, but next week I will try to make a drawing and then do some calculations.
I think that 8inch diameter wheels are a bit to small, I was thinking about more like 15inch - maybe I will just use wheel tires. Or what do you think?
Thanks for the advice regarding wires, connectors etc.
I will suddenly make it fit inside a enclose, as you can seriously get hurt it it suddenly fall over if a wire gets pulled out. Right now I thinking about making a custom PCB for my balancing robot too, so i looks more finished, and just not like a prototype.
I actually had to email robotmarkedplace, because they hadn't validated my account after a week.
@MarkT
Thank you for your advice - especially on those silicone insulated cables. I were also thinking about using XT60 connectors, as I have heard many good things about them - I'm currently changing those tamiya connectors on my mini balancing robot.
You are totally right, but I just thought 90rpm sounded very slow compared to those motors (Pololu - 30:1 Metal Gearmotor 37Dx52L mm 12V with 64 CPR Encoder (No End Cap)) I used for my mini balancing robot, as they had a run speed of 350rpm.
Regards
Lauszus
Calculations.pdf (14.9 KB)