Over time, my great assistant has worn. When it perform duty, it left black mark on the floor. Checking the part at aliexpress.com, it cost almost 1/4 from original price. And since the battery life also left around 40 min, so i decide to removed all the rubber on the wheel both left and right.
I use paint scrapper to remove all the rubber wheel. This the only tool i need.
After all are removed, doing some test run, and the great thing it still can walk,i mean rolling. but its bit slippery and can notice it cant rolling over carpet anymore.just on floor. But its ok for me as long as it can help me with the sweeping work.