Is Trek 3900 Mountain Bike A Good Bike? [Trek 3900 Review]

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The Trek 3900 is a mountain bike in the Trek 3 series. In 2005, it was only $329.99. It falls under the category of low-cost mountain bikes. But it’s a mountain bike that will be with riders for the next ten years. It is worthwhile to spend the time learning about it.

Trek 3900
Trek 3900 2012

In the past, we’ve seen a lot of low-cost bikes put in a lot of effort in terms of price/performance and durability. And the Trek 3900’s durability is unquestionable.

Below, I’ll go over the descents and climbs of this mountain bike, as well as its component features and comparisons to other mountain bikes. Giving you a bird’s-eye view of the Trek 3900.


Trek 3900 bike
Image source: singletracks

To be more specific, the Trek 3900 alpha isn’t a particularly fast mountain bike. It’s designed for normal mountain riding, but because mountain riding can’t be avoided, long descents are included. With only 70mm of fork travel, the Trek 3900 is prone to bottoming out if you come across large rocks or roots on the descent.

The 2.0″ tires deflected easily during the descent, which was a little uncomfortable. The difficulty is further reduced, and the trail’s descending surface is much more comfortable. This is also a once-in-a-lifetime riding opportunity.


The Trek 3900 excels on hill surfaces, and in hilly areas with high and low rolling terrain, gripping the grips can climb small slopes of about 20° very quickly, and with the 3X8 drivetrain, it’s not easy to strain.

It is not always a good experience to want a fast and painful slope; after all, the 26″ tires will always feel a little lacking in transmission when compared to the current 27.5″.

Of course, another important reason is the weight of the body; if you complain about this, you are being unreasonable; after all, it can do more than $300 stacked out of the accessories. As a result, it will only climb on less technically difficult trails.

General pavement

When riding on normal brick-laying or hard-packed surfaces, the Trek 3900 performs reasonably well in comparison to most cheap mountain bikes. The 3X8 drivetrain has a wide enough range of shifts. It’s also very difficult to encounter difficult terrain when riding on city streets.

Trek 3900 Mountain Bike
Image source: singletracks

The park’s wooded areas provide the best opportunity for the Trek 3 series 3900 to perform well, easily passing through cobblestone surfaces or surfaces with some potholes while not interfering with the rider’s ability to ride the entire bike.

The muddy dirt, as long as it’s not too soft and you don’t run out of kinetic energy pedaling, is perhaps the highlight of this mountain bike.

Component Features

Alpha Silver Aluminium frame

Trek 3900 alpha aluminum
Trek Mountain Bike

The Trek 3900 mountainbike is less bulky thanks to the Alpha Silver Aluminium with the semi-integrated head tube, and the double oval downtube with integrated corner stays adds style to the overall design. It is also designed with a greater emphasis on the down tube’s role as a support when climbing ramps.

The slight bulge in the rear insert also allows for larger tire size. A wider 2.2″-2.4″ tire, which is compatible with the Trek 3900 frame, may be considered for more mountain riding. Flat welds have not lost the soul of a good mountain bike.

The 3X8 drivetrain

The older 3X7 drivetrain has fewer gearing options than the 3X8 drivetrain. This is still lagging behind the latest Trek mountain bikes. However, given the asking price, it’s a good value match for the accessories. While many riders consider the Shimano Altus and Shimano Acera M360 to be low-end, they must admit that they are durable.

When it comes to climbing, the right gearing can make or break your ride. In an entry-level mountain bike, a 3X8 drivetrain is still considered a relatively high configuration. The alloy guide wheels, too, don’t feel cheap, and the smooth movement contributes to the ease of use and simplicity.

If you don’t think it’s too much to go after full mountain bike performance, the Trek 3900 drivetrain is a better choice at this price point.

Tektro linear-pull brakes

The Tektro linear-pull brakes are on the low end of the spectrum, and while they are the bike’s mainstay, I couldn’t brake well on fast descents. That is the disadvantage of these brakes.

Of course, if your primary purpose for purchasing it is not strenuous mountain biking, the Trek 3900 brakes are superior. The simple and straightforward rim brakes make riding on flat roads very comfortable, and the mechanical operation and crisp braking that requires some travel also allow you to ride more freely on trails or forest roads. This component isn’t ideal, but with its upgraded Trek 3900 Disc, these annoyances can be avoided.

Fork in the front The Trek 3900 has a fork with only 70mm of travel, the InSync Grind 1. This is adequate for general mountain riding, but not so much when the difficulty level increases. A shock fork with such a short travel is only found on entry-level mountain bikes for youth riding.

And the fork travel on the Trek 820 mountain bike currently on the market is only 75mm, which is slightly more than that but still insufficient for trail riding. As a result, it is appropriate for general trail or rough road riding, and the shock absorption effect of the fork is excellent and will not fail to function.

Tires and wheels

The Bontrager LT3 tires are the same as those used on the Trek 800, which was released at the same time. 26″x2.0″ tires have a greater increase in handling flexibility and provide excellent traction on normal surfaces, but not necessarily in wooded areas after rain.

However, the grip on rough terrain is compromised. Although I prefer wide tires, many Trek 3900 owners have complained about the original size being narrower. Of course, this is upgradeable; as previously stated, it can be the widest and support 2.4″ tires, making your ride on the wet ground a better experience.

Rack and fender mounts

The Trek 3900 can be outfitted with racks and fenders to transform it into a short-distance commuter. Better storage space is required for touring rides. This could be a reason to consider riders who use it primarily for commuting rather than difficult mountain rides.

Other versions of the Trek 3900

Trek 3900 Disc

The original cheap rim brakes have been abandoned in favor of a more cost-effective mechanical disc brake. The rest of the kit doesn’t change much.

Trek 3900 mountain bike Specs

FrameAlpha White Aluminum w/semi-integrated head tube, bi-oval down tube w/integrated gusset, rack and fender mounts, disc compatible dropouts, replaceable derailleur hanger
HeadsetVP-A68-TK, 1-1/8″ semi-cartridge, sealed
StemBontrager Approved, 25 degree
HandlebarBontrager Approved Riser, 30mm rise
SaddleBontrager SSR
SeatpostBontrager SSR, 31.6mm, 20mm offset
PedalsWellgo nylon platform


Rear DerailleurShimano M360
Front DerailleurShimano C051
CrankShimano M191, 42/34/24
ShiftersShimano EF50, 8 speed
CassetteSRAM PG830 11-32, 8 speed
BrakesTektro V w/Shimano EF50 levers


RimsFormula Alloy FM31 hubs; Bontrager 550 rims w/brushed sidewalls
TiresBontrager LT-3, 26×2.0″


  • How much does the Trek 3900 mountain bike weigh?

Trek 3900 mountain bike has an estimated body weight of 32 lbs (14.5 Kg)

  • What frame sizes are available for the Trek 3900 mountain bike?

There are 13, 16, 18, 19.5, 21 and 22.5″ frames.

  • What is the value of Trek 3900 mountain bike?

The estimate is around $60 when the bike is in relatively good condition.

What do we like about it?

  • Affordable price to make it easier for beginners to get
  • Lightweight aluminum frame
  • 3X8 drivetrain with wider shifting range
  • Rack and fenders can be installed for commuters’ needs

What we don’t like about it?

  • 70mm shock fork, not suitable for intense mountain riding
  • Narrower tires for nimble handling, but some grip is lost

Comparison Table

BicycleFrame materialWheel sizeSpeed NumberPrice
Trek 820 mountain bikeTrek Custom Steel26-Inch21Click View
Trek Marlin 6 mountain bikeAluminum27.5-29 Inch10Click View
SANTA CRUZ 5010Carbon27.5in x 2.4in12Click View
Schwinn Bonafide Mens Mountain BikeCarbon Fiber2924Click View
Gravity FSX 1.0 Full Suspension Mountain BikeAluminum26-Inch24Click View


Trek 820 mountain bike vs Trek 3900

Trek 820
Trek 820

Despite the fact that the Trek 3900 has been discontinued, it still offers more benefits than any other mountain bike in the same price range. I compared the Trek 820 mountain bike to the Trek 3900 here. There are numerous distinctions between them.

The Trek 820 has a steel frame, SR Suntour shock fork with 75mm travel, and a 3X7 drivetrain. They all have the same thing, of course: alloy cable pull brakes and 26×2.00″ tires. The Trek 820 is a good alternative to the Trek 3900. It is slightly heavier by 2 pounds and has a standard 3X7 drivetrain with an extremely loosehead tube angle for comfortable mountain riding.

So, when comparing the two, I prefer the ruggedness of the Trek 820, and its use is more suited to the needs of commuter riders. One of the best sports is perhaps the occasional mountain ride.

Learn more: Is The Trek 820 Mountain Bike Really Suitable For Newbies?

Trek Marlin 6 mountain bike vs Trek 3900

Trek Marlin 6 mountain bike
Trek Marlin 6 mountain bike

In terms of accessories, the Trek Marlin 6 is a little more modern than the Trek 3900. Starting with the extremely popular body color scheme, the smooth and clean internal alignment, and the comfortable head tube angle, it is the body design that mountain riders adore.

If you want to become an adventurous everyday rider, the Trek Marlin 6 is ideal. The Trek Marlin 6 has a 100mm (80mm on some frames) travel fork, making it the entry-level shock fork for trail riding when compared to the Trek 3900. There are also safer and more efficient hydraulic disc brakes available, which allow for quick braking with a flick of the finger.

The now-popular 1X10 drivetrain eliminates the obsolete front derailleur chainstay, allowing entry-level riders to ride without feeling the complexity of the setup and be more confident mountain riding and challenging technical trails.

The Trek Marlin 6 costs less than $1000 but outperforms the Trek 3900 in a variety of configurations. The Trek Marlin 6 mountain bike is well worth a look if you want to be an everyday adventurer in mountain riding.

Learn more: Is Trek Marlin 6 Worth Buying? [Trek Marlin 6 Review] 2022

SANTA CRUZ 5010 vs Trek 3900


The Trek 3900’s configuration leaves avid trail riders tasteless and ready to try a high-end trail mountain bike. In fact, the comparison of these two mountain bikes just made me more conscious of how big the gap is between a professional cross-country mountain bike and a casual “toy”.

With the SANTA CRUZ 5010 Carbon CC X01 Eagle Mountain Bike, you get the Carbon CC frame, VPP Suspension, RockShox Super Deluxe Ultimate Rear Shock, 140mm travel, RockShox Pike Ultimate Fork, 140mm, Front Travel, SRAM G2 RSC 4-piston hydraulic disc brake, and more.

You can learn more by clicking on the links below. With these crushing high-end configurations, your off-road experience is about more than just accommodating the bike’s configuration; it’s about enjoying the entire off-road experience.

You can even compete in off-road and endurance races. If you’re hoping for a race like this, the SANTA CRUZ 5010 might just help you win.

Learn more: 2022 Santa Cruz 5010 X01 Review – Napoleon’s Heroism

Final Verdict (4.5/5)

At a low price for entry-level mountain riding needs, the Trek 3900 is a mountain bike stacked with relatively low to mid-range accessories for the time. Able to ride in normal mountain terrain. More than anything else commuter riders would prefer them.

All in all the Trek 3900 is a very good entry-level mountain bike. Rating: (4.5/5)

If you want to see more Trek bikes reviews, follow us as we’ll bring you more evaluations.

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