Reddit mentions of SHIMANO RD-M591 Deore SGS Rear Derailleur (9-Speed, Long Cage, Black)

It's a great bike for the price. For what it's worth, I've done plenty of loaded touring in mountains with similar gear ratios (compact crank with 11-28t cassette). Others will say your lowest gear ratio (1.2) isn't low enough for mountainous touring. Depends on your strength and how much you're carrying.

To get it lower, you can buy an 11-34t cassette which will bring you down to a 1.0 ratio.

However, I'm not sure the derailleur it comes with will fit an 11-34t cassette. If it doesn't, you'll need a mountain bike rear derailleur like this.

In short, you're looking at $30 or $70 to upgrade to a traditional low touring gear ratio, not including labor.

Make sure you get a 9 speed or lower MTB derailleur. Unlike road derailleurs, Shimano has a different pull ratio on their 10 speed MTB derailleurs. If you buy a 10 speed derailleur, it won't be compatible with your shifters.

Something like this Deore M591 should drop right on

This Alivio model should also work, and is a bit cheaper

Either one of those should allow up to a 34 tooth cassette on the small chainring. Just make sure you don't shift to it on the large chainring unless your chain is sized correctly.

I scored this Rockhopper for $50! Now I’m looking to modernize pretty much the whole thing. Please critique my build list below. Would you get anything different, or better, or maybe anything else that would be better value? Did I miss anything? Do you think all of this will work together? It will be my adventure bike for bike packing, gravel, off road touring.

FOMTOR 25.4 stem 60mm 35 Degree Bike Handlebar Stem Riserhttps://www.amazon.com/gp/product/B07G71CZG6

UPANBIKE Road Mountain Bike Bicycle Stem Riser Adapter 1 1/8" φ22.2mm https://www.amazon.com/gp/product/B071LLR8PR

Action 1-1/8" W/Adjuster Black Cable Hanger Fronthttps://www.amazon.com/gp/product/B06XCSKWCQ

KMC X9L 9 Speed Chain Gold Coatedhttps://www.amazon.com/dp/B0789HPV7M

Wheel Set 26 x 1.5, Mavic x M117, Deore M530 9Sp Hub, Blk SS Spokes, 32Hhttps://www.amazon.com/dp/B0033H53VI

Shimano Deore 9-Speed Mountain Bicycle Rear Derailleur - RD-M591https://www.amazon.com/dp/B003OWPRLI

Maxxis DTH 26 X 2.15 60A Kevlar Blackhttps://www.amazon.com/dp/B004XIT4YS

XCSOURCE MTB Mountain Bike Crankset Aluminum Bicycle Crank Sprocket and Bottom Bracket Kit 170mm CS400https://www.amazon.com/dp/B01LWXUV7I

RaceFace 104mm Single Chain Ringhttps://www.amazon.com/dp/B00D3FG6ZW

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Edit: Adding Shifters and Cassette

SHIMANO Deore SL-M590 9-Speed Shift Lever
https://www.amazon.com/dp/B00IKVJF8Y/

JGbike Sunrace 8 9 10 Speed MTB Cassette 11-40T 1 Wide Ratio Including 22mm Extender - for SRAM Shimano-Type splined freehub Body
https://www.amazon.com/dp/B01MRLWHEO

This is tempting then. If all I need to do is drop this in and tension it, I'm probably going to do that vs anything else. Seems like it'll be quite a worthwhile upgrade especially if I can use my existing shifter, chain and cassette !