E-bikes are getting more and more popular these days, and for good reason. With an electric assist motor, you can ride farther, faster, and tackle more challenging terrain than you could on a traditional bike.
However, most e-bikes, especially higher-end models designed for off-road riding, can get very expensive very quickly. In this post, we experiment with converting an affordable city e-bike into a makeshift e-gravel bike on a budget.
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Introducing the Velotric Thunder ST1
The bike we’ll be modifying is the Thunder ST1 from Velotric. This Class 1 e-bike was designed primarily for city commuting and running errands around town. With its low step-through frame, puncture resistant tires, included lights, and basic but practical specs, it’s clear this bike was made for urban transportation.
However, with its lightweight aluminum frame tipping the scales at just 36 lbs total, we wondered if this bike could be converted into a more capable off-road machine. The Thunder ST1 normally retails for around $1,400, making it a very budget-friendly e-bike option. So we were curious to see just how far we could push its capabilities with some simple, relatively inexpensive mods.
Overview of Stock Specs
Before we get to the upgrades, let’s look at what the Velotric Thunder ST1 brings to the table in its stock form:
- Motor: 350W rear hub drive with 45Nm torque
- Battery: 36V 10.4Ah (estimated 280Wh)
- Range: Up to 52 miles per charge
- Top speed: 20 mph with pedal assist
- Pedal assist: 5 levels, torque sensor activation
- Gearing: 8-speed Shimano Altus
- Brakes: Tektro R280 hydraulic disc brakes
- Tires: Velo ThickStreet 26″ x 2.125” puncture resistant tires
- Extras: Integrated lights, phone app connectivity, throttle (on some models)
The 350W motor may seem small compared to higher-end e-MTBs, but it provides smooth, natural-feeling torque with the sensor activation. The battery is fixed to the frame rather than removable, but its 10.4Ah capacity combined with the efficient motor provides claimed range up to 52 miles, which is impressive for an urban e-bike.
The Altus 1×8 drivetrain, Tektro hydraulic brakes, and included lights round out the quality parts selection, while convenient extras like the phone app add nice value for the price. All in all, it’s a well-designed city bike for the price, if a bit heavy at 36 lbs.
Upgrading to Off-Road Capability
To transform the Thunder ST1 from a city slicker to a backroads explorer, we focused on three areas: the tires, handlebars, and pedals.
Wider, Grippier Tires
The first obvious limitation for off-road riding is the stock Velo ThickStreet tires. With their stiff, puncture resistant casing and shallow street tread, they’re simply not suited for trails.
We swapped them out for a set of 700c x 50mm WTB Raddler tires. The increased width and tread depth improve traction and suspension, while the supple casing absorbs bumps much better. Wider tires can also run at lower pressures, increasing comfort and control.
Going from 26” to 700c diameter wheels further improves rollover capability. The difference riding off road is night and day with these grippier, higher volume tires.
More Control with Wider Bars
The other issue is the narrow, curved city handlebars. These are fine for cruising around town, but offer poor control for off-road riding.
We replaced the stock bars with a wider straight alloy bar to provide more leverage and control over the front end. The backsweep places the hands in a natural position, while the wider 780mm width gives more steering authority when maneuvering through obstacles. It’s amazing how much more confident the front end handling feels now.
Proper Pedals for Traction
Finally, the stock plastic platform pedals were replaced with proper wide platform MTB pedals with removable metal pins for traction. Having proper grippy pedals is crucial for standing up and powering over loose climbs without your feet slipping off.
With these simple upgrades – quality off-road rubber, wider bars, and grippy pedals – the Thunder ST1 was transformed into a new kind of machine. Now it was time to hit some trails and see what it could really do.
Riding Impressions
To test out its new off-road chops, we took the Thunder ST1 gravel grinding and bikepacking. The results were impressive: this converted city e-bike handled adventures far beyond its intended realm.
Gravel Cruising
On local gravel and dirt paths, the difference from stock was remarkable. The new tires float over sand and mud patches, and soak up rocks and holes much more smoothly. The wider bars provide a feeling of front end control more like a proper mountain bike. Standing up to muscle through loose climbs is easy with the grippy pedals.
The 350W motor seemed plenty powerful for most moderate gravel terrain. On long inclines, switching to a higher power level would let you spin casually up all but the steepest pitches. The torque sensor activation means the power curve feels seamless and natural. With five assist levels plus a throttle on some models, there’s plenty of support when you need it.
In stock form, this bike would have felt sketchy and out of its element on loose gravel roads. Now it cruises through confidently, expanding the possibilities for adventure far from the city.
Bikepacking Potential
To further test its merits as an adventure machine, we loaded it up with bikepacking bags and gear for an overnight trip. The simple rear rack is just enough to strap a compact bag and tent on. A frame bag fits nicely in the main triangle. Add a handlebar roll with the sleeping bag and you’ve got ample gear capacity for lightweight overnighters.
The Thunder ST1 felt reassuringly stable and capable fully loaded on gravel roads and jeep tracks. The low gearing allowed tackling steep switchbacks when needed. The motor helps take the edge off long climbs with the extra weight. The wider tires and handling inspire confidence in loose terrain, even riding one-handed to snack or sip water.
While the lack of suspension does limit the technicality of trails it can handle, it’s surprisingly adept loaded down with camping gear. For bikepacking easier gravel routes, fire roads, and forest trails, it feels right at home.
Ride Experience and Tech Features
Beyond its surprising off-road acumen, there are a few other features that stand out after logging many miles on the Thunder ST1.
Natural Riding Feel
The torque sensor activation and smooth power curves result in very natural-feeling pedal assist. The bike offers five levels of support plus a throttle on some models. However, levels 2-3 felt ideal for most riding. You simply pedal normally, and it amplifies your efforts in a seamless way. There’s no added resistance when turned off either.
The smaller 350W motor might seem limited next to high-power e-MTBs, but actually provides a nicely balanced ride experience on mixed terrain. The power feels perfectly sufficient yet not overwhelming.
Overall, the pedal-assist system blends in naturally rather than feeling like it takes over. This enhances the cycling experience compared to more aggressive systems.
Refined Design
For the price, Velotric has clearly put care into the bike’s design and refinement. Everything from the clean internal cable routing to the integrated lighting system shows attention to detail often missing from budget e-bikes.
The aluminum frame with subtle sculpting around the motor looks nice and avoids the bulky boxed-in look of some hub motor bikes. The frame battery is sleekly integrated for a minimalist aesthetic. Even small touches like the secure charging port cover demonstrate thoughtful design.
Riding the Thunder ST1 doesn’t feel like you’re on an obvious “e-bike” – the refinement makes it simply feel like a quality bike. The ride quality exceeds expectations for the price.
Range and Charging
Velotric claims up to 52 miles of range from the 36V 10.4Ah integrated battery. Our mixed trail riding suggests 40-45 miles is realistic with varied terrain and assist levels. Either way, this is impressive range from a compact urban e-bike battery.
Charging time from empty is 5-6 hours using the standard 2A charger. So plugging it in after each ride keeps it conveniently topped up. The port is discreetly hidden near the motor. The battery locks into the downtube for security.
For an urban/suburban e-bike, this combination of range and charging makes daily use quite feasible without range anxiety, especially around town. The range is respectable for shorter recreational rides as well.
Phone Connectivity
The app connectivity is a nice premium feature for the price. After pairing with your phone via Bluetooth, the app shows battery status, speed, mileage, and even includes a basic GPS tracker.
The tracking looks handy for theft recovery, though seems a bit redundant given the range limitations of Bluetooth. Still, it’s a thoughtful inclusion, and being able to check mileage and battery level via app is convenient.
This gives you the high-tech feel without complex or expensive smart features. For a sub-$1500 e-bike designed for daily transportation, it hits a nice sweet spot.
Final Verdict
Considering its affordable price and city-focused design, the Velotric Thunder ST1 proved surprisingly capable when converted to a makeshift gravel/adventure e-bike. With some quality off-road tires, wider bars, and grippier pedals, it feels stable and confident on gravel roads and easier unpaved trails. While lacking suspension or ultra high power, it strikes an impressive balance for exploring backroads.
The low weight, natural pedal assist, quality design, and long battery range come together to create a very fun, versatile ride. With its budget price but surprising capability when modified, we can recommend the ST1 as an ideal platform for DIY e-gravel conversion and even bikepacking adventures.
If you want to turn an affordable, practical city e-bike into a more rugged all-rounder, the Velotric Thunder ST1 has proven itself well suited for the task. With some smart upgrades, you can unlock its potential beyond the urban jungle without breaking the bank.
