Originally Posted by
dsbrantjr
If your bottom bracket (that axle between the cranks) is loose, why not just replace that? Replacing working components with new ones in anticipation of future resale will gain you little if anything, if you do eventually resell it.
the 4500 is a HT2 crank, if the axle is FUBAR, then the whole crank is, the BB may still be fine.
For replacing the crank, if the OP wants to go with 5800, it will work, just as a R3000 (Sora 9 speed) or 4700 (Tiagra 10 speedd) will, with the current BB.