Originally Posted by
dvai
Is a new bike. Sirrus X5.0
Has a 40T single ring on the front and a Shimano SLX M7100, SGS, 12-speed rear Derailleur. The cassette on the rear is 11-51t.
What would be the easiest way to improve speed?
Change the cassette? If yes, which ratios?
And would a large cage rear derailleur accommodate that cassette?
What about her speed on the bike are you wanting to improve? If you are a stronger rider and are wanting her to equal your speed, then she is either going to have to get stronger legs or an e-bike.
As long as she doesn't have the same power to weight ratio as you she will always be slower for most things.