Friend is considering building up a SIR9 or a KM. We were trying to figure out the frame weights of each and it is was worth the extra money for the SIR9. Going to be used for bikepacking (geared) and trail use (mix of geared and SS).
It's really hard to pass on the Karate Monkey imo. I just picked up a new Gnot Boost frameset and built it up fixed gear for local trails. The KM has somehow managed to get better every version but stay in the lower end of the price range. This newest version rides amazing, completely different than the older Surlys. I was reluctant at first because I had ridden older versions and wasn't a fan of how stiff the Surlys rode. The new one actually rides extremely well. Couple that with the fact that if you build up a frame set (the black version) it comes with mounts for literally any bikepacking gear you could ever imagine. It's an insanely versatile bike.
The SIR9s ride really well, but if your buddy is going to be using it for bikepacking I wouldn't even consider it next to the KM.
Here is my 2 pennies, I will never buy another Niner, I have several different Niner hardtails since 2010, OG MCR, 2 SIRs (gen 1 and 2), One 9 Scandium, One 9 RDO, 2 Air 9 Carbon. With the exception of the MCR all ran SS. MCR broke, both SIRs broke, ONE Scandium broke, all right after the warranty, while i really liked the ride of the bikes i think the QC for Niner sucks. I still have my Original Air9 Carbon with matching Tang fork it is now my bar bike, still ride my One9 RDO on occasion but I pretty much just ride my new Karate Monkey, I just built it with a Fox 34 at 130 170 dropper, XT brakes, I9 wheels. Bottom line is I think KM would much better suit his needs.
Can't chime in on the SIR9 with anything but what I've read and going from warranty on Niner's to the "springy" description a lot used to describe the SIR9, I wouldn't take the risk. The Monkey is cheap and so versatile, as said, has all the mounting points you could ever want for bike packing and they're know to withstand nearly anything, ideal bike packing frame IMHO.
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