AAIRSK X5 20" Fat Tyre Electric Mountain Bike
SKU: F36202In Stock
SPEED15.5 Mph
RANGE37 Miles
MOTOR250W
BATTERY15Ah
CHARGING5.5 Hours
WEIGHT77 lbs
Adjustable Cycle Helmet£38.99
Front and Rear Light Set£44.99
This Model Is Fully Compliant With UK Road Regulations
This bike is built to comply with UK Electrically Assisted Pedal Cycle (EAPC) regulations, meaning it can be used on public roads and cycle paths without registration, tax, or a licence. Motor assistance is limited to 250W and cuts off at 15.5 mph (25 km/h).
See UK LegislationThis one carries 720 Wh of battery. The maker quotes 37 mi; in mixed riding with some hills, expect nearer 28 mi. A full charge costs about £0.20. Across a year that is roughly £978.00 less than making the same journeys by car, so the bike pays for itself in about 8 months. Everything here is worked out from this bike's own specification. Estimates, not promises: the assumptions are printed underneath.
Range you can expect
| Low assist, flat roads | 37 mi |
|---|---|
| Mixed riding, some hills | 28 mi |
| Full assist, loaded or hilly | 20 mi |
| Riding time on a charge | 2 h 23 min |
What it costs to run
| A full charge | £0.20 |
|---|---|
| Every 100 miles | £0.54 |
| Electricity for a year | £12.00 |
| The same year by car | £990.00 |
| You keep | £978.00 |
| Pays for itself in | 8 months |
Worked out from the specification
| Battery energy | 720 Wh |
|---|---|
| Energy per mile | 19.5 Wh |
| Charger output | 2.7 A |
| Power to weight | 7.2 W/kg |
| You can carry | 441 lb |
Based on £0.245 per kWh, £0.45 per mile to run a small car, and 2,200 miles a year. Charging is costed at the socket, not at the battery.
Carries more than ninety-eight percent of our range
The AAIRSK X5 has one of the highest rated payloads we sell. If you are a larger rider, or you carry tools, shopping or a child seat, this is a frame built with that in mind rather than one that merely tolerates it.
It costs less than three quarters of our catalogue, and of the eighty twenty-inch bikes we stock only seven are cheaper.
Four-inch tyres change what counts as a road
Run at low pressure, tyres this wide turn gravel, wet grass, sand and broken tarmac into ordinary surfaces. The contact patch is large and the bike does not dart when the ground changes under it.
They also work as suspension, which is why the ride stays comfortable on a rigid steel frame.
Small wheels, low frame, easy to get on
Twenty-inch wheels keep the standover height down, so swinging a leg over is easy even with the bike loaded and even with a rack on the back.
For a heavy bike that is not a detail. Mounting and dismounting is where most low-speed accidents happen.
Road legal, so there is nothing to arrange
The motor is 250W and assistance stops at the legal limit, which makes this an electrically assisted pedal cycle in the UK: no licence, no tax, no insurance, no registration.
You can ride it on roads and cycle paths from the day it arrives.
A battery sized for the weight it moves
Fifteen amp-hours at forty-eight volts sits above the middle of our range, which it needs to: fat tyres and a heavy frame use more energy per mile than a light bike on narrow tyres.
The panel below shows the energy it holds and what that works out at per mile.
Steel, and honestly heavy
The frame is steel and the bike is among the heavier ones we sell. That weight is the payload rating; a frame rated to carry this much cannot be light.
Treat it as a bike you ride from where it is stored. On the flat it wheels easily. Stairs are a different matter.
Brakes sized for a loaded bike
Mechanical discs front and rear, and worth keeping properly adjusted on a bike that may be carrying thirty kilos of rider and cargo beyond its own weight.
They are simple, cheap to maintain, and serviceable by any shop or by you.
Charging fits an evening
From empty it takes most of an evening, so the natural rhythm is plugging in when you get home rather than planning around a charge.
Top it up rather than running it flat and the pack will last longer.
What to do before the first ride
It arrives largely assembled. Allow twenty minutes.
- Fit the front wheel, handlebar and pedals
- Set the saddle so your leg is nearly straight at the bottom of the stroke
- Set tyre pressure: soft for grip, firmer for range on tarmac
- Check both brakes before you load it
- Charge to full once before commuting on it
Where it earns its keep
This is a load carrier that happens to look like a mountain bike. A rider who is heavier than average, or who does the weekly shop by bike, gets more out of this frame than out of anything else at the price.
If that is not you, the extra weight is just extra weight.
Not for a long tarmac commute
Fat tyres cost you range and effort on smooth road. If your route is ten flat miles each way, a narrow-tyred bike will go further on the same battery and feel quicker doing it.
The quoted range is modest for the size of the bike and drops further when you ride hard or carry a load. There is no suspension beyond the tyres, and the steel frame is not light. All of that is the price of the payload.
- BRAND
- Aairsk
- CATEGORY
- Fat Tire
- MOTOR POWER
- 250W
- RANGE
- 37 Miles
- SPEED
- 15.5 Mph
- BATTERY
- 15Ah
- WEIGHT
- 77 lbs
- CHARGING TIME
- 5.5 Hours
- BRAKE SYSTEM
- Mechanical Disc
- FRAME MATERIAL
- Steel
- MAXIMUM LOAD
- 441 lbs
- INPUT VOLTAGE
- 48V
- TIRE SIZE
- 20 inch
- TORQUE
- N/A
The AAIRSK X5 20" Fat Tyre Electric Mountain Bike states 250W, 37 Miles and 15.5 Mph, and below it is set against the DYU FF500 20 Inch Fat Tire Folding Electric Bike. Every figure the two disagree on is marked. Choose a different bike to compare it with whichever one you are also considering.
8 of 12 specifications differ. View DYU FF500 20 Inch Fat Tire Folding Electric Bike
- Are the electric bikes brand new?
- Yes. All electric bikes sold by BikTron are brand new, factory-sealed, and sourced directly from authorised manufacturers and official distributors.
- How do I choose the right electric bike for me?
- Pick a bike based on how you plan to ride. City bikes are great for commuting, folding bikes work well if you need compact storage, mountain bikes handle hills and mixed terrain, and cargo bikes are ideal for carrying shopping or loads. If you are not sure, our Bike Quiz can help.
- Are the batteries original and certified?
- Yes. Every electric bike battery is brand new and original from the manufacturer, with full safety certification and performance testing.
- Are the bikes tested before shipping?
- Yes. Each e-bike goes through a quality check before dispatch, covering electronics, brakes, motor response, and battery performance.
- Do electric bikes come with a warranty?
- Yes. All electric bikes from BikTron include a manufacturer warranty. Duration depends on the brand and model. Most bikes include a 12-month warranty as standard.
- How long does delivery take?
- Standard UK delivery usually takes 2 to 7 business days. Remote areas may take a little longer. You will receive a tracking link by email once your order is dispatched.
- Which payment methods do you accept?
- We accept Visa, Mastercard, PayPal, Apple Pay, Google Pay, and Klarna buy-now-pay-later. All payments are processed securely.
- Can I return my electric bike?
- Yes. You can ride the bike and still return it. Tell us within 30 days of delivery and we book the courier and collect it from your door. Contact us first and we will guide you through the process.
- Do the bikes need assembly?
- Most electric bikes arrive 85 to 90 per cent pre-assembled. You will usually need to attach the handlebars, pedals, and adjust the seat. A basic tool set is often included.
- Are BikTron electric bikes legal to ride in the UK?
- Yes. All bikes sold by BikTron that meet UK EAPC rules (250W motor, max 15.5 mph assisted speed, pedal-assisted only) are fully road-legal. You do not need a licence, tax, or insurance to ride them on public roads. Riders must be at least 14 years old.
- What about the electric scooters?
- Those are different, and the law treats them differently. A privately owned e-scooter cannot legally be ridden on a public road, pavement or cycle lane in the UK, whoever sold it. We sell ours for private land use only, with the landowner's permission, and every scooter product page says so. If you want something you can ride to work, choose an electric bike.
Secure checkout and fast UK delivery on every order.
- Free standard UK delivery on most bikes — 2 to 7 business days
- Express delivery may be available on request
- Full tracking included with every order
- Pay securely with Visa, Mastercard, PayPal, Apple Pay, Google Pay, or Klarna
- 0% finance available through Klarna at checkout
Before you order:
- Delivery is to UK mainland addresses — some remote areas may have a small surcharge
- Most bikes arrive 85–90% pre-assembled and include basic tools for setup
- If you are unsure about sizing or specs, contact us before you buy
Full details at Payment & Shipping.
Simple and fair terms so you can buy with confidence.
- 30-day return window — if the bike is not right for you, send it back
- Ride it. It needs to come back clean, undamaged and complete, with the charger, tools and manual
- A refund or replacement is issued after we receive and check the return
Please note:
- For a change of mind we book the collection and deduct its cost from your refund, and we tell you the amount before we book it
- If we sent the wrong item or it arrived faulty, we cover return shipping in full
- All bikes include a 12-month manufacturer warranty as standard
Full details at Returns & Refunds and Warranty.
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18+, UK residents. Credit subject to status. Terms apply.
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Helpful reading
Guides and reviews to help you decide.
ReviewAAIRSK X5 Review, 20 Inch Fat Tyre Electric Bike UK
The AAIRSK X5 is a chunky 20 inch fat tyre electric bike costing £649. Here is our take on comfort, range and build quality based on its published specifications.
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ReviewAAIRSK GT300 Review, Is the Cheapest AAIRSK Good Enough?
Honest AAIRSK GT300 review for UK buyers. We look at what the £499 electric mountain bike gets right, where it cuts corners, and who should buy it.
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