Hi guys - it's my first post so please go easy on me.

OK, 55 year old guy in Sandhurst England who enjoys getting out on his bikes, I have a Giant CRS3 for general road and tow path use and a 12 year old Scott Vail for when I want a bit of off road fun. Just so that you are aware, Sandhurst is in the Blackwater Valley so there are some excellent flat roads, but lots of steep hills up the valley sides.

It's the Giant though where my question lies. This is a stock, off the shelf bike, with Shimano M151 crankset (28/38/48) and SRAM PG380 11-28 Cassette. The bottom end gearing is fine but I am looking to increase the top end gearing to bring it more in line with a road bike (rather than buying another bike which would not go down well believe me), so my question therefore is whether to change the crankset or the cassette?

Clearly I am not looking to spend big money on this because I may as well buy a second hand road bike, so any suggestions would be appreciated.

Thanks

Ian