Rockrider’s E-ST100 is, on paper at least, a £999 electric hardtail mountain bike designed for mixed terrain.
While the rear-hub motor and battery provide decent propulsion and range, the rest of the bike finds its limits when you encounter technical trails.
Conservative geometry and components concessions in order to hit that keen price point hold it back.
It lacks stability on rougher or steeper sections, which undermines confidence – not helped by the lack of power from the brakes and traction from the tyres.
However, keep the terrain more level and the ground smoother, and the E-ST100 is comfortable to ride. While it may not be an all-terrain trail-tamer, it is a comfortable bike to get the miles in on.
Rockrider E-ST100 frame
The Rockrider’s frame is made from 6061 hydroformed aluminium tubes.
The seatstays and top tube feature aggressive curved profiles; I don’t mind the seatstays' aesthetic, but the top tube’s hump is divisive.
The chainstays are asymmetrical to give sufficient chainring clearance while keeping them short.
The down tube also features substantial forming to accommodate the battery, but not to house it internally. Instead, it sits proud in its housing, meaning there’s no mistaking this for a non-electric bike.
A straight head tube with a 44mm internal diameter features up-front with semi-integrated cups. While the fork doesn’t have a tapered steerer tube, you can fit a fork with one down the line.
Other neat features include pannier rack mounts and external cable routing hidden under a lengthy down tube protector. This is neat and shows external routing can be almost as clean as internal routing.
Rockrider E-ST100 geometry
While the E-ST100 is aggressively priced, its geometry isn’t so sharp.
Designed around a 100mm-travel fork and 27.5in wheels, the numbers are conservative. The head angle is a moderate 68 degrees, while the seat angle is a relaxed 73 degrees.
Perhaps the biggest outlier is the reach measurement, with my size-large test bike’s figure reading a minuscule 429mm. The chainstays are short too, at 430mm. All in all, the wheelbase adds up to 1,145mm.
| | XS | S | M | L | XL |
|---|---|---|---|---|---|
| Head tube angle (degrees) | 69.5 | 69.5 | 69.5 | 69.5 | 69.5 |
| Chainstay (mm) | 429.3 | 430 | 430 | 430 | 430 |
| Seat tube (mm) | 346 | 361 | 373 | 417 | 498 |
| Top tube (mm) | 533.2 | 557.5 | 573.3 | 616.6 | 636.3 |
| Head tube (mm) | 100 | 110 | 130 | 140 | 160 |
| Bottom bracket drop (mm) | 25 | 43 | 43 | 43 | 43 |
| Bottom bracket height (mm) | 298.5 | 305.5 | 305.5 | 305.5 | 305.5 |
| Wheelbase (mm) | 1035 | 1054 | 1071 | 1115 | 1136 |
| Stack (mm) | 559 | 587 | 606 | 615 | 634 |
| Reach (mm) | 361 | 378 | 388 | 429 | 443 |
Rockrider E-ST100 specifications
To include a motor and battery, Rockrider has inevitably cut some spec corners, and the E-ST100 is not as well-equipped as non-motorised hardtail mountain bikes costing £1,000.
The fork is a basic SR Suntour XCT30 with 30mm stanchions and 100mm of travel. A quick-release skewer, rather than a thru-axle, holds the 27.5in wheel in place.
The rear hub, containing the motor, is bolted into the rear dropouts.
The Rockrider-branded wheels are wrapped with Rockrider All Terrain 2.25in tyres, although these are not tubeless-compatible.
Microshift and KMC largely take care of the eight-speed drivetrain, including the derailleur, chain and a cassette with 11-34t range.
Tektro’s TKD68 mechanical disc brakes are teamed with 180mm rotors front and rear.
Rockrider E-ST100 ride impressions
I tested the E-ST100 on a range of trails, varying from fire roads and gravel paths through to lower-graded blue and red mountain bike trails around my local trail centres in Bristol and the Forest of Dean.
To test the bike's everyday usability in a more urban environment, I also used it for a handful of short commutes.
Conditions were mostly dry, with a few rainy rides thrown in for good measure.
Rockrider E-ST100 climbing performance
Heading uphill, the E-ST100 is a decent performer given the price. It has its limits, though.
The geometry puts you in an upright position, despite the lengthy 80mm stem and fairly slack 73-degree seat tube angle.
It's certainly comfortable, but feels out of its comfort zone when things get technical.
Keeping the front wheel planted is a challenge on steeper, rougher climbs. Its geometry is a reminder of why the trend for steeper seat angles has boomed. This isn’t helped by the rearward weight bias, caused by the rear-hub motor. The result is a slightly wayward feel.
The All Terrain tyres roll quickly though and, on smoother climbs, the bike trucks along at speed.
The hard-compound, low-volume tyres struggle for traction; more voluminous tyres with a slightly softer compound would help, without detracting too much from the bike's rolling speed. It would also improve comfort thanks to the ability to run lower tyre pressures.
Given the wheels are tubeless-ready, it's a real shame the stock tyres aren’t as well.
The Microshift drivetrain offers decent performance; it's smooth enough clicking from gear to gear. The shifters aren’t the most ergonomically designed though, making it a stretch to reach them without adjusting your grip on the bar.
The limiting factor is the cassette’s narrow gear range. Combine the eight-speed unit’s meagre 11-34t spread and 32T chainring, and steeper climbs become a struggle, even with the help of the motor.
A wider-range cassette wouldn’t bump the price up too much, but would open up its capabilities to deal better with the steeps.
On smoother, flatter climbs, then, the E-ST100 is a competent companion, but steep and technical climbs are not its forte.
Motor performance, battery life and urban riding
The rear-hub motor is a strong performer, offering up a claimed 240W of maximum assistance and 42Nm of torque, with three assistance modes to choose from. This is combined with a 380Wh battery.
The Rockrider powers along in the higher ‘2’ and ‘3’ levels of assistance comfortably. On all but the steepest sections, it has enough poke to keep the speed up. It’s relatively quiet and the power delivery is smooth.
It won’t keep pace with more expensive, full-power electric mountain bikes but, for the price, it's impressive.
The LCD display gives ample information and the controls are easy to use. Its location makes it easy to switch between modes and turn the motor on or off, with the soft-touch rubber buttons.
The 380Wh battery provides an impressive range. In comparative testing, the Rockrider covered 30km and 600m of climbing in the middle ‘2’ mode and still had two of the five bars of indicated battery life remaining.
Rockrider E-ST100 descending performance
The E-ST100 rolls along flatter, less technical terrain with reasonable confidence. However, as soon as you start to encounter more technical trail features, it struggles.
While I didn’t lose the chain when descending, no clutch on the derailleur and no frame protection means there's a lot of chain rattle on rough terrain.
The basic SR Suntour fork has a pronounced top-out and, with no rebound-damping adjustment, it fires back at you from compressions. What’s more, with 30mm stanchions and a quick-release axle, they can feel flexy.
A lack of bite from the brakes and tyres compounds the issue. While the brakes have mid-sized 180mm rotors, the mechanical Tektro calipers lack the power needed to keep the speed of this 22.2kg machine in check on steep descents.
The own-branded All Terrain tyres have a hard rubber compound. There is also limited volume and cushioning from the narrow 2.2in width. I irreparably damaged the rear tyre on a mellow blue trail while testing at Ashton Court in Bristol.
The head angle is fairly steep, while the reach and wheelbase are short. Together the stability, and thus your confidence, isn’t as high as bikes with more progressive geometry.
The placement of the motor in the rear hub also means a large portion of the bike's weight is positioned right over its rear end, rather than centred around the middle where you want it. This is particularly noticeable when airborne; the rear end comes back down to earth rapidly.
On mellower terrain, things are better.
Here, the E-ST100 is a comfortable place to be; the aluminium frame itself is not overly harsh, and the grips and saddle are fairly comfortable.
The tyres roll quickly enough. When not pushing hard on technical terrain, they have acceptable levels of grip on hardpark, tarmac and loose gravel.
On less technical singletrack, you can work around the geometry and spec foibles, and still have fun.
Overall, it’s best treated like an MBT-style electric hybrid, rather than a true beginner's or budget electric mountain bike.
It can handle a variety of, if not all, terrain types, as long as it doesn’t get too steep or technical.
Rockrider E-ST100 urban and commuting performance
The Rockrider makes light work of the daily commute.
It rolls quickly along tarmac, with minimal noise coming from the tyres. While they are small-volume for true off-road use, on tarmac, they provide decent cushioning. They provide acceptable grip too.
The brakes still lack bite and the limited gear range is a hindrance on steeper urban climbs, but that won’t be an issue for everyone.
It’s a decent commuting companion, although I believe it would be even more able to perform duties here with larger 29in wheels.
