Can I replace Shimano Claris crankset FC-2450, 50/34t for Shimano 105 53/39t?
The FC-2450 uses a Octalink bottom bracket. A newer 105 crankset would be a Hollowtech II, so at the minimum you'd need a new bottom bracket. You'll also need to make sure you can position the front derailleur for the change in teeth (probably can), and probably get a new chain to account for the extra teeth.
That being said, if you want a bit of change in gearing, changing the cassette rather than the crankset is probably easier and cheaper.
If you goal is to change the gearing, better options are to change the cassette or just the chainrings rather than the whole crank-set.
If you are looking for a cheap crank upgrade, and have noticed that there are lots of lightly used Shimano 105 FC-5600 53/39 double cranksets out there for sale because many people changed to a 52/36 mid compact or 50/34 compact crankset, there are some things you should consider.
- Changing to 53/39 will mess up your gearing.
- You'll need a new chain which adds to the cost.
- Claris to 105 is a big jump - the progression being Claris, Sora, Tiagra, 105. You won't really gain any benefit because the rest of the bike will still be at Claris level.
You will probably be better off upgrading shifters and derailleurs - or - saving up for a whole new upgraded bike.