Hey stretch. Well, if you’re running 48:14 you’re pretty much running a suitable track gearing anyway - roughly 90 inches - so if you’re capable of riding that on the street then you can keep it the way you have it. Most people recommend somewhere around 70 inches for normal street riding.
I don’t want to doubt what you’re saying but that’s pretty extreme, are you sure you’re riding 48:14, if i’d have noticed that when we were at the track i would have stolen your bike for a spin.
you wont get any faster with a bigger ratio than that, if anything you may get faster with a smaller ratio and some practice spinning.
Smaller ratio = acceleration.
usually I run a ratio about the same as yours but I went on a long distance ride the other day with 48:18, went down one hill at a bit over 60kph and was spinning with a cadence of 178RPM, I think you should just concentrate on booting your cadence, at ~180RPM with your ratio you should be able to get up to ~80kph, good luck stopping though!
Re the wearing out cranks, make sure your BB has the correct taper for the cranks, if it is different your cranks will loosen