sloar 

I’m doing a minor upgrade on my 2020 Marlin 5. I want to leave it 3x7 because I don’t want to change much. So what is my options on a rear derailleur upgrade? I’m switching to a new Deore front derailleur. I’m seeing nice XT and Deore rear derailleurs but they list as 1x or 2x . Will they work on a 3x? Thanks

veganbikes

So 3x7 on a modern bike is certainly not worth upgrading, the rest of the parts on the bike are not really ideal for a mountain bike.

Deore is going to be 10 speed or now 11 speed and XT is going to be 11 speed or 12 speed it is going to be incompatible with 7 speed (which originally came out in the late 80s early 90s).

Run the bike into the ground and find a bike with the components you want. Look for something with a proper air fork and ideally thru-axles and all the modern stuff that is common now and then you have a good option for upgrades.

Darth Lefty 

Pretty much any 7-8-9 speed Shimano MTB derailleur will work. But it's not going to change your bike any. Get a better fork. Or tires, grips, saddle.

xroadcharlie

I agree with Darth. Unless you are having problems with the rear derailleur, I wouldn't change it. It looks like your bike has Shimano's bottom of the line Tourney rear derailleur. Don't let that fool. Even there low end gear performs just fine, better then some models from other brands costing much more. That's why they are so popular.

I had the Tourney rear derailleur on my comfort bike and it worked flawlessly until clumsy me stepped on it. The dealer replaced it with the sturdier Altus model, Which I'd recommend only if yours gets damaged.

Murray Missile 

I'm a little late to the party but you can use any long cage 7. 8 or 9 speed Shimano compatible RD, the 10 speed RD's however use a slightly different cable pull and won't work correctly on anything but a 10 speed. I've read that the 2020's had the frame holes for internal dropper post cable routing, is this correct? I have a 2021 Marlin 5 and it has the hole at the front of the down tube but not the other holes, I think you had to step up to the Marlin 7 in 2021 to get the other holes. I'm doing some upgrades to mine as well......

I got mine as a trade in on an old truck. Guy bought it during the COVID panic and had set it up like a hybrid with a big fat Serfas "sofa" for a saddle and a Deda stem riser, cell phone holder, computer, lights, etc. He then proceded to ride it a few times and then let it sit for the next 2 years so it is still like new. I didn't need it but it's my size and I love the Metallic Copper or whatever Trek calls it and after 12 years I'd had enough of the truck so a deal was made. It's nice frame but with WalMart level components, but at least it has a freehub and not a freewheel!

I just happened to have quite an accumulation of new parts from other projects that changed directions along the way which included an FSA Afterburner 42-32-22 10 Spd triple crankset & MegaExo BB; Deore XT 3X10 front & rear deraiileurs (I'm old, I need a triple), SRAM 10 speed cassette and a SRAM 10 Spd chain. I took one look at the 3X7 Tourney on that nice frame and knew I had found a home for my 10 speed parts. After one quick test ride across my relatuively flat back yard I also knew a better fork was in order as well. I'm 67 years old as of today and just had both knees replaced recently so my off road activities are going to be pretty mild, no jumps to speak of and nothing technical so I don't need too much in the line of suspension but something better than the XCE28 that came on it. I picked up a Suntour XCR32 with air suspension and remote lockout. There are better shocks but it fit the budget and is "good enough" for my intended use, actually a bit more than I need truth be told but I can live with that.

I got the bike just a few days before my first knee surgery back in June and I am just now getting where I can ride a bike again so nothing had been done to the Marlin. Yesterday I finally pulled the stem riser and put an Adamo Prologue saddle on it and took it for a short ride, it felt MUCH better with just those simple changes, except for that gawd awful mushy fork. The Bontrager wheels are OK for the short term but eventually I want to run larger tires so wider rims will be needed. I'm just getting into building my own wheels so I picked up a set of Deore hubs and SunRingle MTX-33 29 inch rims to build a new set of wheels for it. The Tektro hydraulic brakes are OK but my OCD compelled me to pick up a set of Deore M6120 4 piston front and M6100 2 piston rear hydraulic discs. It will see gravel with some serious downhills and I'm a bit of a Clydesdale so I want GOOD brakes...... I would have liked to have a Deore XT crankset too but I have the FSA and it looks good on the bike so it stays, for now. I hope to get everything changed over this Winter but I have a couple of other builds I need to finish up first.

Are these upgrades economically practical or even necessary? Oh, hell no! The whole project is entirely illogical but I have the parts, the bike and the time and I'm having fun.


As received:

sloar 

I got the bike pretty cheap, bought it off the original owner that rode it once and out it up. I ended up cutting the handlebars down a bit, upgrading the fork to a Rockshox Recon, Deore RD and Sora FD, IXF cranks with their external bottom bracket, Rockbro pedals and a new chain. I cut about 5lbs off, living in central Indiana which is flat 3x7 gears work fine. So far I’m pretty happy with the setup.

Murray Missile 

Nice looking bike. I'm in extreme West Central Illinois where the prairie ends and the roling hills of the Mississippi River Valley begin. Depending on which road I take out of town I can have nice flat terrain with only small hills or nothing but up and down for miles and while some of the hills while maybe not long by some standards they're pretty steep. Somebody a few decades younger could manage them with a 3X7 or a good 1X or 2X but not me, not now anyway. I used to do it on my '97 Trek 820 rigid MTB with the stock 3X7 Altus group but that was back in 1997, these days I need more gears LOL. I still have the old 820, it's full 3X9 Deore XT now though, always was a sucker for puttin' lipstick on pigs LOL. I need to get it out and rinse the dust and cobwebs off it, it's been a few years since I've ridden it, I think I'll go do that right now.

Darth Lefty 

Sora FD is shifting ok with the MTB shifter? As a longtime Shimergo enthusiast I'm interested in this stuff

sloar 

Shifts fine, it doesn’t trim so setting up took a awhile to get it just right.