Ultra wide ratio 2x9 transmission.

[Jurassic]

I recently re-assembled an old fat bike using a 1x9 transmission (Sunrace 11-40 cassette with a 30t NW chainring) and it seems to work very well so far. This has set me thinking that it might be an idea to lower the bottom gear on my bikepacking bike which has a 2x9 transmission (currently a 11-34 cassette) and I was wondering whether to try getting another 11-40 cassette instead of going for 11-36. The rear mech is an XT Shadow medium cage (9speed) and I know I might need to use a range extender. Has anyone tried building an ultra wide ratio 2x transmission? Any advice? FWIW I've never regretted lowering the gearing on a bike (especially when carrying luggage).

[Richpips]

Worth a go, but I think if the chain is long enough to run big-big then the derailleur won’t take up the chain slack in small-small.

[whitestone]

What's the capacity on the derailleur and what's the gap between chainrings? As Rich says it'll be the derailleur that will limit you, Shimano are conservative (with a small 'c') regarding their derailleur capacities but I've pushed 2T past it with no problem and I wouldn't expect 4T to be of concern but that might depend on the derailleur.

[ScotRoutes]

I'd take the Shimano rear mech specifications with a pinch pf salt. On my Amazon, I'm using an Ultegra rear mech with a published capacity of 39T but it's handling 45T just fine. It'll do big-big and small-small too.

[Jurassic]

Yeah I had wondered whether having the chain long enough to go big/big would leave it too slack on small/small. I might nick the 11-40 off the fat bike and mock it up and see, that way I don't end up buying anything until I know whether it'll work or not (it'd also allow me to know whether I need a goat link thing as well). Thanks folks.

[gairym]

I'll check on my Solaris when I get home tomorrow but I'm running a 2x setup and in my head it's 11sp with an 11-42T out back (but I could be totally wrong).

Watch this space.....