Upgrading basic MTB (Trek Marlin 6) for "type 2 fun" gravel rides?

I have a Ti gravel bike with GRX Di2…I absolutely love it but I can’t bring myself to take it on any really gnarly gravel rides. It wasn’t cheap and with parts availability being what it is, I don’t want to risk trashing the derailleur or worse in muddy/gnarly “type 2 fun” rides. I was signed up for unPAved, for example, but couldn’t make it due to a family commitment. After seeing the mud and route I’m glad I didn’t ride it to be honest.

I bought a Trek Marlin 6 this year for easy bike trail/neighborhood rides with my son and he has a matching Precaliber 20. I’m thinking of possibly adding some upgrades (tubeless wheels, maybe 1x drivetrain) so I can still ride with him but also use it on rough gravel rides without worrying quite so much about breaking something!

I’m sure some would say it’s not worth upgrading or maybe buying a different bike, but I love that we match when we ride and it gets my son excited to get out on his bike! I think the 135mm QR rear hub limits alot of what I can do. I also know it’ll never be light, but I’m OK with that since I’m 6’5" and well north of 200 lbs.

Any advice? The 2x8 groupset actually works well, but I’d love to have a dropper and the convenience of 1x. can I get a 1x10 or 1x11 groupset to work with this bike? Is the fork suitable for more than easy bike trail rides?

I should add…I’ll won’t be doing any “proper” mountain biking with this. I broke my finger riding a MTB last year, and my wife will make me sleep in the garage if anything like that happens again!

I’d think that you can ride this bike on most of the gravel you’d want to ride a bike on. 29” wheels, 100mm suspension fork, room for 2.2 inch tires - it’s basically the equivalent of an XC hardtail from a few years ago.

The dropper post is a key upgrade! And it will work with this bike - I think you’ll probably want a dropper with external cables (not internal). I’d lean towards going to the LBS to get one unless you definitely know which model you want and have installed drivetrains before.

I personally think tubeless wheels can wait until you find yourself consistently riding stuff that is super-bumpy, and/or you do two consecutive gravel rides where you flat on the current wheels.

1x is really nice. However, the drivetrain is a wear item, so I’d say ride it until you’ve worn out the cassette and chainring, then replace it.
Your bike has the Shimano HG free hub body, so you can put up to a 10-speed road or 11-speed Shimano MTB drivetrain on it. I’m not sure about SRAM.
When you put the drivetrain on, you’ll need to put on:

  • Chainring
  • Cassette
  • Chain
  • Rear derailleur
  • Shifter for the rear

That’s why I’d suggest waiting until you wear it out or until you’ve dropped the chain in a couple of rides in a row.


Awesome…thanks for all the tips! One thing that seemed convenient about 1x is that the dropper lever could replace the left shifter. Would it be clunky to have a dropper and shift lever there?

I haven’t installed a full drive train, but I have swapped shifter cables, a bottom bracket, and replaced a derailleur successfully. I think I could manage it…but I hear you on the wear and cost concerns!!!

Glad to hear this bike could be up to the task though. With “good” bikes being so expensive, I wasn’t sure what was realistic to expect from a modestly priced one.

“Good” just means the right material, geometry, and components for what you want to do with it.
“Expensive” means that it’s probably really lightweight.

There are several different kinds of dropper levers - one that replaces the left-hand shifter, one that is an “on-top” version - so you can use it with your lever. If you look closely at your handlebar and at some of the images of dropper levers, you’ll get a sense of where it will get positioned.

There’s no harm in replacing the drivetrain and the dropper at the same time - it’s just that you can still get the value out of the drivetrain before replacing it.

Sorry - one other thing you’ll need to replace when you go to 1x - the crankset. You’ll want to have a chainline that’s optimized for 1x - so your 1x chainring would be positioned halfway between the small and big chainrings on your current crankset (when you look down at it from the saddle).

Something else to consider - ride the bike as-is on progressively more interesting gravel. You’ll know the places where a dropper would make you feel more comfortable (because you’ll either need to get behind the seat, or because you feel like you’re perched too high on the bike during a descent).

My one question for you - have you identified the gravel that you’ll need this for? If so, go for it? If you just “want to be prepared” - it’s totally fine to ride the bike as-is, until you have a ride where you were clearly wishing for the upgrades…

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I want to do unPAved next year…even just for that, based on the pics I saw from this year, it would be good to ride the Marlin vs my current gravel bike. I’m more worried about completing these rides safely rather than trying to race them. I’m sure 2.2" tires would give me some confidence.

I think the dropper is a must. I’ve done a few rides this year where descending was terrifying because I couldn’t get low enough. I have alot of seatpost showing since I’m so tall.

I think you have your answer… :slight_smile:

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:star_struck: I think so!! :star_struck:

I really appreciate the help. Just wanted to make sure I wasn’t (too) crazy.

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