The front wheels of Roomba Discoveries collect hair and eventually stop turning. This undoubtedly affects performance, particularly cleaning time before recharge, but more importantly, it really bothers me when a robot isn't working at its peak.
Here, I show how to remove and clean the front wheel. This is a surprisingly complex task and will take some time. My Roomba sat on the kitchen counter for a few days as I devoted half an hour here and there to figuring it out. If you are lucky, it is possible to accomplish this without removing Roomba's cover; I was not lucky and had to remove the top cover and bumper. If you're not prepared to spend some time, and potentially remove Roomba's covers, don't start.
I probably sent more time on this project than I would have spent sweeping the floors for the next year. But, that's not the point, is it? I'll watch Roomba work for nearly as long as it would take me to do the same job. I've seen other people do this too, so I know I'm not alone. Cleaning, servicing, and ensuring perfect operation of a Roomba is a way to constructively harness obsessive compulsive behavior.