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Bike models › Hybrid

Trek FX 2 Gen 4: specs, upgrades and what fits

A light aluminum fitness hybrid with a simple 1x9 Shimano CUES drivetrain, hydraulic disc brakes and mounts for a rack and fenders. Best for: Fitness rides and commuting.

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My take, from the specs

A light, easy fitness hybrid for commuting and rides, about 12.1 kg, with hydraulic disc brakes that stop well in the wet. The Shimano CUES 1x9 with an 11-46 cassette is simple and has a very low gear for hills, and there are mounts for a rack and fenders. Tires top out at about 40 mm, so it is not built for rough trails.

Sizes: XS: 4′10″–5′1″ (147–155 cm) · S: 5′1″–5′5″ (155–165 cm) · M: 5′5″–5′9″ (165–175 cm) · L: 5′9″–6′1″ (175–186 cm) · XL: 6′1″–6′6″ (186–197 cm)

Stock specs

TypeHybrid
Year2026
Price when new$850
Sold atTrek dealers / trekbikes.com
Wheels700c × 35 mm tires
Gears1×9 · 40T · 11–46T
BrakesTektro HD-R280 hydraulic disc, flat mount
ForkTrek FX Alloy, flat-mount disc, 410mm axle-to-crown
Rear derailleurShimano CUES RD-U4000
ShifterShimano CUES U4000, 9-speed
CrankProWheel Pro alloy, 170mm
Bottom bracketGeneric Sealed cartridge, 68mm
AxlesQuick release
Seatpost27.2 mm
Weight26.7 lb (12.1 kg)
SizesXS, S, M, L, XL
Stock colorsCarbon Dark Grey, Fjord Blue, Fury Red

Upgrade limits

How far each part can go on this frame, and why. Measure your own bike to confirm the estimated ones.

PartLimitWhy
Widest tire (current wheel size)40 mmNo measurement yet. Estimate from owner reports and frame design. Your 20 mm internal rims suit roughly 29–52 mm tires.
Other wheel sizes650b up to ~47 mmDisc brakes don't care where the rim sits, so a 650b wheel with a fatter tire fits. A 650b × 47 is about the outer size of a 700 × 28, so the bottom bracket sits about 12 mm lower than on 700 × 40 (watch pedal strikes).
TubelessNot recommendedTubeless needs a rim built to seal (bead hook + channel) and tubeless-ready tires.
Valve typeSchraderDecides which tubes and pump heads fit. Presta tubes fit Schrader rims with a grommet; not the other way.
Replacement wheelsQuick release · 100/135 mm · 6-bolt discAny wheel matching axle type, spacing and brake mount fits. Rear also needs the right freehub.
Biggest rear cog46T (now 46T)Set by the rear derailleur (Shimano CUES RD-U4000): max low sprocket 46T, total capacity 35T. A hanger extender can add a few teeth (hit-or-miss on non-Shadow derailleurs); a new derailleur is the reliable way to get more.
Front gears1x (40T)One ring, no front derailleur. Adding a front derailleur needs a mount on the seat tube and a 2x crankset, so most riders change the ring size or cassette instead.
Chainring sizeUp to 44T (now 40T)Estimated from similar frames. Measure the chainring-to-chainstay gap to confirm. Check whether your ring is bolted or riveted. Spindle length (? mm) sets chainline; a big change in ring size may need a different BB spindle.
Gear count upgrades9-speed (HG body)Shimano HG 8/9/10-speed freehub: takes 8, 9 or 10-speed cassettes, Shimano 11-speed MTB and CUES/LinkGlide cassettes (7-speed needs a 4.5 mm spacer; most 11/12-speed road cassettes need an 11-speed road freehub, though the 11-34 HG700/HG800 fit). Shifter,…
Cranks & bottom bracketSquare taper · 68 mm shell · ? mm spindleAny square-taper crankset fits with the right spindle length. Upgrading to Hollowtech II needs a new BB (same threaded shell).
Pedal thread9/16" × 20Every adult multi-piece crank uses 9/16". One-piece kids/cruiser cranks use 1/2".
Brake padsTEKTRO E10Disc pads only fit calipers with the matching shape.
Rotor size160/160 mm now · front 160 (flat mount: check fork)6-bolt rotors. Going bigger needs a caliper adapter: flat-mount adapter, and many flat-mount forks are rated 160 mm max. Most steel forks allow 180 mm; check the fork if a max rotor is printed on it.
Caliper upgradesHydraulic systemHydraulic: match the brand of lever and caliper.
Stems & bars1-1/8 steerer · 31.8 mm bar clampAny stem for a 1-1/8 steerer with a 31.8 mm clamp fits. You can cut a bar narrower but not wider.
Drop-bar conversionPossible with modsNeeds road brake/shift levers (microSHIFT R8 makes 8-speed ones that pull Shimano 8-speed cable correctly), a drop bar, tape, and road-pull brake calipers because road levers pull less cable. Usually $250+.
Seatposts27.2 mm27.2 mm is the most common size: suspension posts and external-cable dropper posts are easy to find. Internal droppers need internal routing the frame does not have.
Racks, fenders, bottlesRack ✓ · Fender ✓ · 2 bottle · Fork cargo ✓Threaded eyelets at the dropouts and seat stays take a rack and fenders. Fork leg mounts take cargo cages.
Max load (rider + cargo)300 lbWheels are usually the weak point under heavy loads. Stay under this with rider plus luggage.

Best upgrades by area

Three options that fit the Trek FX 2 Gen 4 as-is in each area, from budget to best. ★ marks the one most worth the money. How we pick. Typical US prices, checked October 2026. They change often: check the price at the store.

AreaGoodBetterBest
TiresContinental Contact Urban 700x40 (40-622) wire (pair)
$$$ ★ Our pick
WTB Byway 700x40 (pair)
$$$
Schwalbe Marathon Almotion 700x38 (40-622) V-Guard Addix (pair)
$$$
Brake padsTektro E10.11 resin disc pads (2 sets)
$ ★ Our pick
Kool-Stop D620S sintered disc pads, Shimano B01S / Tektro E10.11 shape (2 pairs)
$$
SwissStop Disc 15 RS organic disc pads, Shimano B-type / Tektro E10.11 shape (2 pairs)
$$
Grips & tapeBudget ergonomic lock-on grips
$
Ergon GP1 ergonomic grips
$$ ★ Our pick
Ergon GP5 ergonomic grips with built-in bar ends (S or L)
$$$
SaddleWTB Volt saddle
$$
Fizik Terra Argo X5 saddle (150 or 160 mm)
$$$
Ergon SR Allroad Core Comp saddle (men's or women's)
$$$ ★ Our pick
PedalsRace Face Chester composite flat pedals
$$ ★ Our pick
Crankbrothers Stamp 2 aluminum flat pedals (small or large)
$$$
OneUp Components Aluminum flat pedals
$$$
ChainShimano CN-HG601-11 11-speed chain (fits CUES 9/10/11, 116 links)
$$
Shimano CN-LG500 LinkGlide chain (CUES 9/10/11, 126 links)
$$ ★ Our pick
Shimano CN-HG901-11 11-speed chain (XTR/Dura-Ace, SIL-TEC, 116 links)
$$
CassetteShimano CUES CS-LG400-9 LinkGlide cassette 11–36
$$ ★ Our pick
Shimano CUES CS-LG300-9 LinkGlide cassette 11–36
$$
—
RotorsShimano SM-RT56 160 mm 6-bolt rotor (1 rotor)
$ ★ Our pick
Galfer Wave 160 mm 6-bolt rotor, 1.8 mm (1 rotor)
$$
Shimano SM-RT86 Ice-Tech 160 mm 6-bolt rotor (1 rotor)
$$
Chainring & crankSquare-taper 1x narrow-wide crankset 44T 175 mm
$$ ★ Our pick
Shimano CUES FC-U4000-1 square-taper 1x crankset 40T
$$
Velo Orange Single Ring crankset with narrow-wide 42T (110 BCD, square taper)
$$$
SeatpostSuspension seatpost 27.2 mm (budget)
$$ ★ Our pick
Redshift ShockStop suspension seatpost 27.2
$$$$
Cirrus Kinekt 2.1 Aluminum suspension seatpost 27.2 mm (LR or XR spring)
$$$$
Bar & stem35° rise 60 mm stem
$ ★ Our pick
Redshift ShockStop suspension stem 31.8 (±6° or +30°)
$$$
Redshift ShockStop PRO suspension stem 31.8 (±6°)
$$$$
LightsPlanet Bike Beamer 200 + Blinky Squared USB light set
$$ ★ Our pick
Cygolite Metro Plus 800 + Hotshot Pro 150 USB light set
$$$
Trek (Bontrager) Ion Pro RT + Flare RT light set
$$$
Racks, bags & fendersTopeak Explorer rear rack (disc mount)
$$ ★ Our pick
Topeak Super Tourist DX Tubular rear rack (disc)
$$$
Tubus Disco steel rear rack for disc brakes (26" or 28"/700c)
$$$
WheelsWeinmann Zac19 700c 6-bolt disc rear wheel, QR 135, 36H, HG 8–10 speed
$$$ ★ Our pick
Shimano / DT Swiss R500 700c disc wheelset, QR 100/135, Center Lock, HG + 2 Shimano SM-RT54 160 mm Center Lock rotors
$$$$
HUNT 4 Season Gravel Disc X-Wide wheelset (QR 100/135, HG, Center Lock) + 2 Shimano SM-RT64 160 mm Center Lock rotors
$$$$

Upgrades that fit as-is

Tires

Tubes

Gearing

Brakes

Comfort

Control

Utility

Drivetrain

Wheels

Fits with small changes (31)

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Buying one used? Fair prices

Worked out from the price new ($850), age and condition, not live market data. If it needs tires, a chain or brakes, take off what fixing them would cost.

Condition1 year old3 years old5 years old
Like new$480–$630$390–$510$315–$415
Good$420–$555$340–$450$275–$365
Fair$345–$455$280–$370$225–$300
Needs work$265–$350$215–$280$175–$230

See what these really sold for on eBay · Other used bike prices

Articles about this bike

Geometry (size M)

Stack594°
Reach393 mm
Head angle71°
Seat angle74°
Chainstay447°
BB drop65 mm
Wheelbase1070 mm
Head tube165 mm
Seat tube420 mm
Standover754°

Compare with

Sources: The Bike Shop: 2026 FX 2 Stepover Gen 4 specs + geometry · Schellers: Trek FX 2 Stepover Gen 4 (crankset, standover, price) · Gear West: Trek FX 2 Gen 4 (max tire 700x40, bar widths, max chainring)