Cool. Well, as a 50t sproc will cost around £45 give or take, i've decided Mr Yamaha actually didnt get it too far wrong with 15/48, im getting 54mpg with a 50 mile a day commute through central london.
Now i'm trying to gt the best deal/VFM for a chain/sprox kit, but DID seems to be coming up around £100 which is a bit steep for me