Trek Marlin 5 Gen 3 Upgrades: What to Do First and What to Skip

The Trek Marlin 5 Gen 3 is a good hardtail, although there are many problems we can talk about. But in my opinion, there are two things that you should upgrade. One is that it doesn’t come with a dropper post, and the other is the fork.

However, considering its price range, I’m pretty satisfied with this bike. So, in this article, I’ll talk about Trek Marlin 5 Gen 3 upgrades, and I’ll try to keep the total cost under $500.

Because if we spend more than that, the cost will get much closer to the price of the Marlin 5 itself. So, we’re not going to go with such a big budget.

What the Marlin 5 Gen 3 Comes With

If you bought your Trek Marlin 5 Gen 3 after 2024, you’ll get these specifications:

• Fork: SR Suntour XCT 30 (coil spring, 100mm travel, no rebound adjustment)
• Drivetrain: Shimano CUES U4000, 9-speed LINKGLIDE, 11-46 cassette
• Brakes: Shimano MT200 hydraulic
• Wheels: Bontrager Connection rims with 2.2-inch wire-bead tires
• Dropper: not included from the factory

When it comes to geometry and other specifications, it’s good. It has a 66.5-degree head angle, 2.4-inch tire clearance at both the front and rear, and internal dropper routing built into the frame. This will make installing a dropper post cleaner later.

But one more thing I want to tell you is that it has a LINKGLIDE cassette, which is designed to work with compatible CUES LINKGLIDE drivetrain components.

So, LINKGLIDE and standard Shimano HG cassettes may look similar, but you shouldn’t assume they’re interchangeable within the drivetrain.

When replacing worn-out parts, make sure you choose compatible CUES components.

Swap the SR Suntour XCT 30 for a Fork With Rebound Adjustment

The Marlin 5 Gen 3 comes with an SR Suntour XCT 30, which is pretty decent for a bike that costs less than a thousand dollars.

It’s good for smooth singletrack, and you can even avoid upgrading if that’s where you are going to ride most of the time.

However, the problem I found is that it has no rebound adjustment or air pressure adjustment, so you can’t tune it to your weight or control how quickly it returns after hitting an obstacle.

And here are a few things you need to remember about your bike before choosing a replacement fork.

• Straight 1-1/8-inch steerer: The Marlin 5 Gen 3 has a straight head tube, not a tapered one. So, you want to make sure the replacement fork has a compatible straight steerer. In most modern forks, you will get tapered steerers.
• 9x100mm quick-release front axle: Your bike uses a 100mm quick-release front hub, not a 15mm thru-axle or Boost 110mm spacing. So, you need a replacement fork that supports your existing front wheel.

Make sure both specifications match before ordering a replacement fork.

My two recommendations are the RockShox Judy Silver TK Solo Air and the RockShox Recon Silver RL.

Both are available in straight-steerer, 9x100mm quick-release versions, with different travel options.

The Judy Silver TK Solo Air is a good upgrade if you want an air spring that you can adjust to your weight. The Recon Silver RL is another option, with 32mm stanchions compared with the Judy’s 30mm.

One fork I’d avoid is the Judy Gold RL, because most versions you’ll find have a tapered steerer and Boost 15x110mm spacing.

These won’t fit your bike, and you will need a headset conversion and a new front wheel.

Add a 31.6mm Dropper Post

The Trek Marlin 5 Gen 3 comes with an internal dropper post routing system built into the frame from the start, with the cable running through the downtube and seat tube. That’s why the installation looks so clean. The cockpit stays clean, and you won’t have to deal with external housing.

But yes, routing the housing will take more work because you may need to remove the bottom bracket to thread it through the frame.

You’ll need a 31.6mm seatpost, but the travel you choose will depend on your frame size, saddle height, and available insertion depth.

Don’t choose a dropper just because someone recommends 150mm for your frame size.

If you’re not sure, you should measure it yourself.

Check how much of the seatpost can fit inside the frame and how much length you need to reach your normal saddle height.

Also, compare the dropper’s total length and minimum insertion requirements before ordering.

So, here are a few recommendations that you can consider.

• PNW Coast: A good option if you want a dropper with built-in suspension. It has 40mm of additional suspension travel and is available in a 31.6mm diameter with 120mm dropper travel. You can also choose an internally routed version for the Marlin 5 Gen 3.
• OneUp V3: Get it if you need a more conventional dropper post with different travel options. It has a 31.6mm version and is worth considering if you want to get the most travel that your frame and saddle height will allow.

By the way, if you can’t operate the remote that comes with your dropper post comfortably, you can upgrade to a Wolf Tooth Remote or an RNW Loam Lever.

Both are designed to improve operation, but make sure you choose the correct mounting option for your bike’s dropper post.

Connection Rims Are Not Tubeless-Ready, So Choose Better Tires Instead

The Marlin 5 Gen 3 doesn’t come with tubeless-ready rims. It has Bontrager Connection rims, so you can’t set up tubeless tires on the stock wheels.

Although I recommend going tubeless because you don’t have to worry as much about punctures, and small punctures can often be fixed easily with sealant, you’ll need tubeless-compatible rims to do that.

So, if you want to keep your stock wheels, you can still upgrade to better clincher tires and use inner tubes.

The stock tires are 2.4 inches wide. You don’t need to increase their width. Instead, you can choose better tires with a folding bead, improved grip and more sidewall protection.

I recommend the WTB Trail Boss 2.4 TCS. It offers good grip and rolls reasonably fast.

For dry and faster trails, you can also consider Maxxis Ardent 2.4 EXO tires. You can use them on both the front and rear wheels.

Replace the VP-536 Nylon Pedals With Metal-Pin Flats While You’re at It

The Marlin 5 comes with VP-536 nylon pedals, which are fine for basic riding, but they don’t offer enough grip when you’re riding in muddy areas, and your feet can slip a lot.

That’s why you can consider different types of pedals, such as metal-pin flat pedals.

Personally, I recommend OneUp Composite pedals for almost every generation or series of Trek Marlin, whether it’s the Marlin 7, 5, 4 or 6. They have a large platform and enough metal pins to keep your feet in place, even on rough trails.

But if you want full alloy pedals, you can also consider the Deity Tmac or Chromag Scarab, although they’ll cost more.

Along with that, you can also get Ergon GA3 or Race Face Half Nelson grips.

What you get with Marlin 5 is the stock Bontrager grips, which are thin and don’t absorb vibration very well on rougher trails.

But these options can make your hands feel more comfortable, especially during longer rides. The Ergon GA3 has a small wing that supports your palm, which can help reduce pressure on longer rides.

Do not Upgrade the Drivetrain

We’ve talked about several things that you can upgrade on the Marlin 5 Gen 3, and these upgrades can add up to a lot of money.

I don’t think you should spend $400, $500, or more on a bike that costs less than $1,000.

So, in my opinion, don’t upgrade the drivetrain because you already get a CUES U4000 1×9 drivetrain with a 11-46 gear range. This is enough for most trails, and you can use it on almost every type of trail. It’s durable and offers good performance as well.

When the cassette wears out, you can replace it with a CUES LINKGLIDE-compatible 9-speed cassette, such as the Shimano CS-LG400-9 or CS-LG300-9.

One chain upgrade I can recommend, especially if you ride in wet or muddy conditions, is the Shimano CN-LG500 LINKGLIDE chain.

It’s designed for this drivetrain and is a good replacement when your stock chain wears out.

But again, if you want to upgrade, you can. My first recommendation, however, is to avoid spending money on the drivetrain.

FAQ

Does the Trek Marlin 5 Gen 3 have internal dropper routing?
Yes, and it’s one of the best things about the Gen 3. The cable runs through the downtube and seat tube.

What fork fits the Trek Marlin 5 Gen 3?
RockShox Judy Silver TK Solo Air and Recon Silver RL are good options, plus they’re compatible.

Tapered or Boost forks won’t fit without a headset conversion adapter and a new front wheel.

Can I run a 12-speed drivetrain on the Marlin 5 Gen 3?
Actually, the rear hub has an HG freehub body, so SRAM Eagle HG cassettes like the PG-1210 are compatible.

Shimano’s 12-speed Deore and above use Microspline and won’t fit the stock hub without swapping the wheel.

So you’ll have to go for a full SRAM drivetrain swap, which is costly.

What tire clearance does the Marlin 5 Gen 3 have?
Up to 2.4 inches, and stock tires are 2.2-inch wire bead.

If you move to a 2.35 or 2.4-inch folding-bead tire, it’ll be a direct improvement with no clearance issues on 27.5 or 29-inch wheel sizes depending on frame size.

What’s the head tube spec on the Marlin 5 Gen 3?
It’s straight 1-1/8 inch, semi-integrated, and not tapered.