Originally Posted by elemental

Are you doing this because you want new cranks or because you want a larger gear ratio? If it's the second, 38T is fine, you could just get a smaller cog and save a lot of money. I have a bike set up 39/17 right now, and while I wouldn't use it for serious road riding, it's perfect for cruising downtown. Ask BMX riders, small drivetrains are stylish:



[Obligatory sentence about marginally increased drag/chain wear on smaller drivetrain using misapplied and misremembered high school physics]