But a major orthopedic surgery this past spring made big differences in Tim's legs, and now he's striving to walk better than ever before.
Tim's objectives for his summer at Bay Cliff Health Camp are easy for him to explain.
"My goals are to walk straighter and to walk without any assistance," said Tim.
Tim spends at least an hour every day with Bay Cliff physical therapist Christy Osborn. She has already seen big differences in Tim since he arrived this summer, which was just one day his casts from surgery were removed.
"When he came, he could walk 20 feet," recalled Osborn. "Now we're three weeks in, and he's walking 450 feet."
Tim's exercises include leg raises and heel slides. He feels loose and well rested after a good day of therapy and tight and sore after a less than stellar day. No matter the result of each session, Tim's optimism keeps him going.
"The way I motivate myself is to keep pushing harder on the therapy," he said.
In the week ahead, Tim will spend more time walking when he's not in his therapy sessions. He focuses on how well he walks instead of distance.
Osborn explained more goals of his therapy.
"Using his arms less because he's putting a lot of pressure through his arms right now, so we want him to be using his legs more," she said. "He has a really nice quality with how he walks."
Tim shows that he can hold that quality for longer distances, building up to the summer's ultimate goal.
"We're hoping by the time camp's done, he'll be good to go without his walker," Osborn said.
On your TV6 Morning News, we will follow Tim throughout the rest of his summer at Bay Cliff, tracking his progress and learning more about this teenager who is inspiring others with his perseverance.