Si wrote:Never had one before but my new road/gravel bike has one. I'm far from convinced.
I think I've only used the big ring about twice. The little ring is OK for road work but struggles at lower end off road on the steeper loose stuff. I'd imagine that it would also struggle on road fully loaded in the hills.
To my mind they've done it the wrong way around: rather than replicating a middle plus a big chain ring of a touring triple they should have done a middle plus a grannie. When I use my touring triple I rarely use the big ring, mostly in the middle but a bit in the grannie. I seem to spend all my time in little chain ring but on the smaller sprockets which is a recipe for wearing stuff out quicker.
But then I'm old and broken.....I remember when all I needed was a 52/42 and a big sprocket of 26....seemed to get me up the local Shropshire steep hills OK.
Might have to swap the chain rings for something smaller.
Modern MTB chainsets don't have the right chainline for a road bike. MTB is usually 50mm offset and a road bike likes 43.5mm. An MTB chainset on a road bike gives a very bent chainline on big ring to the larger sprockets. Small ring to big sprocket risks the chain unshipping then jamming agin the frame.
I like low gears too, even on the fast summer bike. I also like close ratio for the faster gears but have no need of 50X11 .. or 50X12. 50X13 is high enough for all except racing fellows. 50X14 is enough for me, even when sprinting for the village signs. (Look up the speeds you obtain for the various ratios, tyre sizes and cadences).
So, I have a 50-34 chainset and a 14-36 10-speed cassette. This gives a low ratio for the really steep heaves and a high enough top gear for sprinting or doing 30mph on the flat with the wind behind. The cassette is 14-15-16-17-19-21-24-28-32-36.... close ratio at the fast end with leg-easer gaps at the slow end. You have to disembowel and recombine two cassettes to get a 14-36 as no one sells a ready-made in those ratios.
You might need a compatible (same as STI road lever pull ratio) MTB rear derailleur, although the latest Shimano long-arm road mechs will probably take a 36 sprocket (they seem to be designed for a 34t maximum but usually have some extra capacity, in practice).
A bonus of these ratios is that I can stay in the big ring even at quite low speeds, as 50X32 is not too cross-chained. This is handy for the bumpy routes when the speed of a ride constantly goes from 10mph to 25mph and back again.