Hi. I only use my Dawes Kovert on the street now, but it's very slow because of the gear ratios and the fat knobleys. I was wondering if it's worth changing the tyres and gears. I only use the 3 or 4 of the fastest gears. It's got 7 cogs on the wheel and 2 on the crank. Or should i just get a new bike? Any advise would be welcome, like 'what tyres' or 'how to do the gears'. Thanks