Trek Fuel+ MX 9.9

A flagship e-MTB for lively, assisted trail days

The Trek Fuel+ MX 9.9 is for the rider who wants a serious helping hand on the climbs without losing the active, responsive feel that makes a good trail bike fun to throw around. It is Trek's flagship mixed-wheel Fuel+ model, pairing a mid-power TQ HPR60 motor with a removable 580 Wh battery, 160 mm front and 150 mm rear suspension, and a descending-focused carbon build. The official UK RRP is £10,300, placing it firmly in premium territory, and current offers appear below.

It suits committed intermediate to expert riders particularly well, whether that means squeezing in another loop after work, linking trail centres on a big weekend ride, or taking on steep natural descents and jump lines. The motor provides 60 Nm, 350 W of published power and up to 200% support. That is enough to take the sting out of repeated climbs while keeping the riding input central, rather than delivering the dominant shove associated with the strongest full-power e-MTBs.

The current Fuel+ MX 9.9 build

The current UK model is the Fuel+ MX 9.9 X0 AXS Gen 2. Its standard specification is lavish: Fox Factory suspension, SRAM X0 Eagle AXS Transmission shifting, SRAM Maven Silver brakes, carbon wheels and a Fox Transfer Neo wireless dropper. It is a build intended to arrive ready for demanding riding rather than prompt a shopping list of performance upgrades.

Retailer year suffixes do not automatically mean a different frame generation, so the Fuel+ Gen 2 and X0 AXS build names are the useful identifiers. Customised Project One orders can have different equipment from the standard bike, however. Pedals are not included, so factor in a suitable flat or clipless pair from the outset.

Fuel+ Gen 2: more battery, more ways to set it up

Fuel+ Gen 2 is the successor to the Fuel EXe Gen 1 platform, with the model name changing from Fuel EXe to Fuel+. The new chassis brings the 60 Nm TQ HPR60 motor, a removable 580 Wh battery and a colour display on this 9.9. Battery removal is a genuinely useful everyday advantage when the bike lives in a shed or garage but charging is easier indoors. Trek publishes a charging time of about three to four hours for the main battery.

There is room to stretch the day further with the optional 160 Wh Range Extender. It is not supplied with the bike, and needs the approved side-load cage, retention strap and connection cable, but it gives occasional long-route riders extra capacity without making every shorter outing carry the extra battery.

The Gen 2 frame can also be reconfigured between EX, MX and LX formats. That adaptability is useful, although changing from MX is not a casual rear-wheel swap. It requires the matching rocker link, lower shock mount, wheel and suspension arrangement, while a change in rear-wheel diameter also needs a Trek retailer to update the e-system. Choose the MX layout because it suits your riding now, then treat conversion as a considered future project rather than a quick tweak.

Why the MX format feels eager on the way down

The OCLV Mountain Carbon frame uses Trek's ABP suspension layout and runs an MX rocker link and lower shock mount in its stock form. A 160 mm Fox 36 Factory fork works with 150 mm of rear-wheel travel from the 205 mm x 60 mm Fox Float X Factory shock. There is substantial scope here for rough, steep and demanding trail riding, with a progression adjustment available to tune the suspension feel.

Every size has a 29-inch front wheel and 27.5-inch rear wheel. The large front wheel is there to help it hold a line over roots and rocks, while the smaller rear gives more clearance and should make the bike easier to rotate through tight turns or lift on a jump. Trek positions MX as its more agile option than the full-29-inch EX and LX arrangements. The nominal 64.2-degree head angle adds reassuring composure, while size-specific proportions and chainstays help the handling remain balanced from S through XXL.

The stock tyres underline that intention. A MaxxGrip Assegai up front and a MaxxGrip DoubleDown-casing Minion DHR II at the rear prioritise grip and impact protection when the trail is wet, loose or properly rocky. They will feel slower on mellow woodland loops and long surfaced links, so a faster-rolling replacement can make sense once the original rubber is worn if that becomes the bike's regular work.

Premium kit where it matters

Fox's 36 Factory GRIP X2 fork and Float X Factory shock offer a highly adjustable, supportive suspension package for riders who enjoy setting a bike up carefully. SRAM Maven Silver four-piston brakes with 200 mm HS2 rotors provide the stopping hardware to match, while the carbon Bontrager Line Pro 30 wheels help support the bike's lighter, more responsive brief. Trek claims 19.02 kg for a size M fitted tubeless with sealant and no inner tubes.

SRAM X0 Eagle AXS Transmission gives the bike wireless 1x12 shifting with a 10-52T cassette and 32T chainring. It removes a mechanical gear cable and is designed to shift under load when correctly set up, but it also adds another battery to the charging routine. The Fox Transfer Neo dropper is wireless too. Keep both component batteries topped up before a big ride and carry a spare AXS battery when being caught short would spoil the day.

Looking after a high-end electric trail bike

Regular care is part of owning a bike at this level, especially after wet UK rides. Clean grit from around the pivots and suspension, inspect the replaceable chainstay guard, and dry the charging contacts before charging. Tubeless sealant needs maintaining, while suspension, brake pads and rotors will need normal attention as the miles and descending build up.

Chain contact with the replaceable guard in the 10T sprocket can occur and is not automatically a sign that the drivetrain is out of line. Inspect the guard for wear and replace it when needed rather than letting it become a small problem that turns into an expensive cosmetic one. The removable battery, electronic drivetrain, wireless dropper and TQ system also make a Trek/TQ-capable workshop a valuable part of long-term ownership.

What changed from Fuel EXe Gen 1 to Fuel+ Gen 2

The previous Fuel EXe Gen 1 platform used a 50 Nm TQ HPR50 motor, 360 Wh battery, monochrome display, 140 mm rear travel, a 150 mm fork and two 29-inch wheels. Fuel+ Gen 2 moves to 60 Nm, a 580 Wh battery and the configurable EX, MX and LX frame system. For a rider weighing up an older Fuel EXe against this bike, the larger removable battery and MX-specific handling are the headline changes, alongside the more adaptable chassis architecture.