Help picking a motor

Hi,
I’m new to robotics and am currently making an around A4 size wheeled robot with two motors and one castor (my first robot). It currently weighs around 800g, although this will change. The motors I was using originally were just cheap yellow motors, but I’ve found them not powerful or fast enough, and so am looking for two replacement motors. I need DC motors with gearboxes that can be powered on batteries providing 9v.
Ideally, as well, I’d like them to be a reasonable price - around £10 - £15 each maximum.
As I don’t know the statistics of my current motors, and know very little about choosing motors, I was wondering if anybody on here could give me any guidance on which are the best motors to pick?
Much thanks,
Dulcie

Hi Dulcie,

We have two nice dynamic tools that might come helpful for you:
Drive Motor Sizing Tool
Drive Motor Sizing Tutorial

About your current motors, do you have any information about the wheel that you have ?
They might or not be compatible with the new motor but we can try to make them work with an adapter.

We have some nice “low cost” gear motors HERE. But have plenty of other brands as well.

All the best,

My current wheels are just cheap yellow ones that came with the motors, and I haven’t found them that good either, so I was planning on buying new wheels once I’d picked the motors.
Thanks,
Dulcie