KOOLUX X9 Pro Review, Dual Battery Fat Tyre E-Bike Tested

If you need an electric bike that can handle rough terrain and go the distance, the KOOLUX X9 Pro might catch your eye. It offers dual batteries, chunky fat tyres, and a powerful 750W motor. But is it the right choice for UK riders?

We put the X9 Pro through its paces on potholed city streets, muddy bridleways, and gravel paths. In this review, we share everything you need to know before buying. We cover range, comfort, UK law, and how it stacks up against other fat tyre e-bikes in our store.

Unboxing and First Impressions

Our KOOLUX X9 Pro arrived in a large cardboard box with sturdy foam padding. The bike came partly assembled. We needed to attach the front wheel, handlebars, pedals, and seat. The manual was clear, and we had the bike ready in under 30 minutes.

The first thing you notice is the thick, aggressive tyres. They measure 4 inches wide and give the bike a rugged look. The frame is aluminium and feels solid. The paint finish is glossy, with Koolux branding neatly applied. We tested the black and red colourway, and it turned heads on the street.

What’s in the Box?

Inside, we found the bike, two battery packs, a standard UK charger, pedals, tools, and a basic manual. The batteries were partially charged, so we topped them up before riding. All components were well protected, and there were no scratches or missing parts.

Build Quality and Design

The welds on the frame are neat, and the cable routing is largely internal for a clean look. The bike feels heavy at over 30 kg, but that is expected with dual batteries and a fat tyre setup. The kickstand is sturdy, and the saddle has a comfortable shape with decent padding.

Overall, for a bike at this price point, the build quality impressed us. It is not a sleek commuter, but a tough workhorse ready for adventure. We also own the Koolux X9 Mini, and the Pro feels like its bigger, more capable sibling.

Key Specifications and Tech

The KOOLUX X9 Pro is built around a 750W rear hub motor. That is far more than the UK’s legal limit for an Electrically Assisted Pedal Cycle (EAPC). We will cover the legal side later, but it’s important to know upfront. The motor peaks at around 1000W and provides strong acceleration.

Power comes from two removable 48V lithium batteries. Each has a 12.8Ah capacity, giving a combined 24.5Ah. That is roughly 1200Wh of energy. On paper, that should deliver an impressive range. The bike uses a cadence sensor, so the motor kicks in as soon as you turn the pedals.

Motor and Battery Power

The 750W motor is not subtle. In the highest assist level, the bike surges forward with little effort. You can climb steep hills without breaking a sweat. The throttle is also fitted, though we will touch on its legality on UK roads in a moment. The motor is relatively quiet, with a faint whine under load.

The dual batteries sit behind the seat tube and on the down tube. They can be used together or one at a time. A handlebar switch lets you choose which battery to draw from first. This is handy if you want to save one for the return journey. Charging both from empty takes around 10 hours.

Fat Tyres and Suspension

The X9 Pro uses CST 20x4.0-inch tyres. These balloon-like tyres run at low pressure, soaking up bumps and providing loads of grip. We found them excellent on loose gravel and damp grass. On tarmac, they hum a little but roll surprisingly well.

The bike has front suspension forks with around 60mm of travel. They take the edge off potholes but are not designed for heavy off-road jumps. The seat post is not suspension, but the squishy tyres and padded saddle mean you rarely feel jarred. If you are used to a skinny-tyre city bike, the ride comfort here is night and day.

Range Test: How Far Can You Go?

We tested the range in three scenarios. First, in the highest assist with lots of throttle, we managed around 30 miles. That may not sound enormous, but it was on steep, muddy trails. In eco mode and pedalling gently on flat cycle paths, we got over 70 miles. This matches the claimed 60–80 miles.

For most riders, that means you can commute all week on a single charge. Or enjoy a long weekend adventure without range anxiety. Carrying a spare battery is not needed because the two batteries are already on board.

Real-World Range with Dual Batteries

On a mixed ride of 40% trail, 60% road, using assist level 3 out of 5, we covered 45 miles before the first battery drained. That left the second battery at about 60%. So with careful management, you can easily reach 60 miles. The LED display shows battery level for each pack, so you always know where you stand.

Bear in mind that range drops in cold weather, with heavy riders, or on very hilly routes. Still, the X9 Pro’s dual batteries address the biggest worry most e-bike buyers have: running out of juice. Compare this to the single‑battery Vitilan T7 Pro, where you might need to carry an extra charger.

Charging Time and Battery Care

Each battery takes around 5 hours to charge from empty. With one charger, you are looking at a full 10 hours to recharge both. We recommend charging overnight. The batteries can be removed and charged indoors, which is safer and better for battery health in a cold UK garage.

Like all lithium batteries, you should avoid leaving them fully drained for long periods. A partial charge is best for storage. Biktron offers a one‑year battery warranty, which is standard. If you ride daily, the batteries should last 500–800 charge cycles before noticeable degradation.

Ride Comfort and Handling

The X9 Pro is a big bike. It is tall and wide, so smaller riders might find it cumbersome. The seat height can be adjusted, but the standover height is fixed. We found it comfortable for anyone above 5ft 7in. The wide handlebars give you loads of control.

With the fat tyres, the bike feels planted. Corners are stable, and it tracks straight even at 20 mph (on private land). The weight means low‑speed manoeuvres need more effort, but the motor helps as soon as you start pedalling.

On Tarmac: City Commuting

Around town, the X9 Pro turns heads but does not filter through traffic like a slim hybrid. You will feel bumps less, though. The throttle lets you zip away from lights quickly, but remember that using it on public roads is not legal if the bike exceeds 15.5 mph. We kept assist at level 2 for a smooth city ride.

The bike is so comfortable that you might take the long way home. The upright riding position gives good visibility. Just watch out for door‑zone cycling, as the wide tyres need a bit more space.

Off-Road: Trails and Gravel

On forest fire roads and gravel tracks, the X9 Pro shines. The fat tyres float over loose stones and grip on climbs. We tackled a 15% gradient in assist 4, and it powered up without hesitation. The cadence sensor responds quickly, though there is a brief delay on steep hills before the motor engages.

On really rough, rooty trails, the front fork works hard, but the rigid rear can feel bouncy. This is not a full‑suspension mountain bike, so stick to bridleways and towpaths. For true singletrack, you might prefer a lighter e‑hardtail. But as a versatile explorer, the X9 Pro is a hoot.

Brakes, Lights, and Safety Features

Stopping power comes from mechanical disc brakes with 160mm rotors. They are adequate for most conditions but require more lever effort than hydraulic brakes. In the wet, they worked fine after a few squeezes to clear the pads. You can upgrade the pads if you ride in hilly areas.

Integrated lights are a welcome feature. The front LED is bright enough for unlit lanes, and the rear light doubles as a brake light. We appreciate that you do not need to clip on extra lights. The bike also has a horn and reflectors, helping you be seen.

• 160mm mechanical disc brakes front and rear
• Bright LED headlight with 3 modes
• Rear brake light activated by brake levers
• Side reflectors and wheel reflectors
• Loud electric horn

UK E-Bike Law and Licence Rules

There is a big elephant in the room with the KOOLUX X9 Pro: its 750W motor and throttle. Under current UK law, an EAPC must have a motor no more than 250W, assist only up to 15.5 mph, and the throttle must stop above 3.7 mph unless it only operates while pedalling. The X9 Pro exceeds these rules.

This means, strictly, it cannot be ridden on public roads, cycle paths, or anywhere with public access as an EAPC. It would be classed as a moped, requiring registration, insurance, a driving licence, and a crash helmet. The bike is sold for off‑road use on private land with permission. You can read the full rules on Gov.uk.

Is the KOOLUX X9 Pro Road-Legal?

No, in its standard form it is not road‑legal in the UK. Some riders choose to restrict the power via settings, but that may not be enough to comply fully. We urge you to understand the law before buying. Many customers enjoy this bike on private estates, farms, or while camping. It is also popular for off‑road leisure.

If you need a strictly road‑legal fat tyre e‑bike, Biktron offers options with 250W motors. Check our Mountain Bikes collection for compliant models. Always check the latest regulations on legislation.gov.uk.

Who Should Buy the KOOLUX X9 Pro?

This bike suits riders who have large gardens, farmland, or access to private tracks. It is also a candidate if you enjoy off‑road adventures at country parks or dedicated trails where motor vehicles are allowed. The dual batteries make it excellent for long days exploring.

If you plan to ride mostly on public roads, we recommend looking at legal alternatives. The same fun can be had with a 250W fat tyre bike, you just trade some top speed for peace of mind.

Best Use Cases

• Exploring private farmland or estates
• Off‑road leisure in areas without public access
• Camping trips where you can ride around the site
• Beach riding (saltwater requires extra care)
• Snowy conditions where fat tyres excel

Comparisons to Other Biktron Bikes

If you want similar off‑road ability but need road legality, consider the ENGWE X26 Dual Battery Electric Bike. It has a 250W motor and complies with UK law. For a lighter, folding fat tyre bike, the KOOLUX X10 Folding Electric Bike is a cracker. And for pure cargo capacity, the KOOLUX X7 Cargo Electric Bike might be your match.

Our all guides hub compares many models side by side, including the popular AAIRSK range if you are on a tighter budget. See our AAIRSK brand verdict for more.

Our Verdict: Pros and Cons

The KOOLUX X9 Pro is a grin‑inducing machine with immense torque and incredible comfort. Its dual‑battery range is a game changer for long rides. The build quality is solid, and it comes with thoughtful extras like integrated lights.

However, its 750W motor means it sits in a legal grey zone. If you stick to private land, it is brilliant. But if you need a daily driver for UK roads, this is not the one. The weight and size also make storage a challenge if you live in a flat.

Pros:

• Huge range from dual batteries
• Plush ride thanks to fat tyres
• Powerful motor tackles steep hills
• Integrated lights and horn
• Sturdy build

Cons:

• Not UK road‑legal without modification
• Heavy to lift and manoeuvre
• Mechanical brakes could be better
• Cadence sensor has slight lag

Overall, for the right person, the KOOLUX X9 Pro offers a thrilling ride that no road‑legal e‑bike can match. Just make sure you understand the rules before you buy. If you are ready, grab the KOOLUX X9 Pro here and start your off‑road adventures.