Originally Posted by
TurbineBlade
Or you could just leave it as it is and coast downhills at 25-30 mph instead of 35-40 (or whatever). I rarely ever need gears higher than 80" or so and suspect that many commuters don't either.....unless you are griding your knees away at slow cadences (poor technique) or just really enjoy flying down hills (which I no longer do since having a bad accident during a race).
Just a thought -- whatever you like.
Since the OP is specifically looking for ways to increase his speed, I'm inclined to agree that the gearing on his bike is too low. My rigid framed MTB from the 90's has a 48 T large chainring so I was surprised that his bike only has a 42. Obviously it was designed for comfort more than speed which is fine, -unless you want more speed.
20 mph at 90 rpm just isn't enough if you care at all about going fast.