I had a new chain and cassette fitted yesterday. But today, hills which I could easily climb two days ago are now horrendously challenging. What was a pleasure has just become a nightmare. Why is this happening? What should I do?
The bike is a Specialized Tricross, about 4 years old. Never had new rear cassette before, but has had new front cogs, new derailleur, and previously one new chain. The bike appears to work OK when on a rack. See my comment below, please.
Edit. Update with new information: Counted teeth as follows: front 50/30, rear 28/11. There are eight rear cogs. The front cogs were changed a year ago, so I have been accustomed, and the shop advised at the time, original size was now obsolete. It would seem that the rear cassette changed ten days ago is a different size to original, and it seems this may explain my struggling to ride with same positioning of gears as previously. Each of the numbers I have quoted here I counted twice. Seems a different size of cassette was fitted