Originally Posted by
dvai
My wife bought a Sirrus X5.0.
Has a 40T crank. The rear cassette is 11-51T
I wonder if switching that 40T to a 42T would make a big difference in terms of speed. We don't live in an area with lots of hills.
Thoughts?
Spinning out a 40x11 on flat roads is not as easy as people think.
With the stock 38mm tires, 80rpm in the 40x11 = 23.81mph. 100rpm = 29.76rpm
If you upsize to a 42T, those numbers will go up to 24.91mph and 31.23mph.
I run a 44T on my 1x CX bike for summer gravel/dirt becuase I was occasionally spinning out the stock 40T (with an 11-32 cassette) when hammering in group rides, big tailwinds, descents, etc.
I can't imagine spending enough time at those speeds on a Sirrus to warrant swapping to a larger ring, but that bike also has a massive 11-51 12sp cassette, so even with a 44T there would still be plenty of low-end gearing for any small hills.