Some advice needed, I've managed to get a mate to come road cycling with me, he's a mountain biker and is just getting the hand of the shifters, bars and riding position, so I'm letting him use my winter/spare bike, which is a Raleigh Sprint http://www.evanscycles.com/products/raleigh/sprint-2010-road-bike-ec023528
The problem he's having is keeping spinning up some of the hills i ride even on the 25 gear, so i want to make it easier on him so that he doesn't just give up on me and i'm back to riding solo
So my thought is to change the cassette, but without changing anything else, so here's where i'm stuck, how big can i go without changing derailleurs and shifters
Could i just switch out the 12-25 for this 11-30 http://www.ebay.co.uk/itm/Shimano-Altus-8-Speed-Bike-Cassette-11-30-CSHG...
or can i go even bigger? as i've see this 11-32 http://www.ebay.co.uk/itm/380362834060?ssPageName=STRK:MEWAX:IT&_trksid=...
Just want to give him as much range as possible without costing me a fortune, ideas please