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Rotwild R.EX Ultra on testOnly 21.6 kg - super-light e-bike with a long range

Adrian Kaether

 · 29.11.2024

Light or full power? The Rotwild R.EX shows that opposites are not automatically mutually exclusive.
Photo: Max Fuchs
At 21.6 kilograms, the Rotwild R.EX competes with many a light e-bike. And that's despite the powerful Shimano motor and large 800-capacity battery. However, the price of the Ultra model is also steep. Can the premium all-mountain bike from Dieburg justify this on the trail?
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Few e-MTBs have attracted so much attention this year like the new race enduro Rotwild R.EXC with the wild rear triangle à la banana swingarm. And Since testing the R.EXC Pro at the latest, we know that: The bike is also a real hit on the trail. But not everyone needs a race enduro right away. That's why the R.EX trail version has been available since Eurobike. Slightly less suspension travel and a record-breaking low weight promise maximum riding fun on the trail. The thick battery with practical quick-release is almost as much a part of Rotwild as the deer on the head tube.

Rotwild R.EX Ultra: Shimano EP801 // 820 Wh // 160/150 mm // 29/27.5 inch // 21.6 kg // 11490 Euro.Photo: Max FuchsRotwild R.EX Ultra: Shimano EP801 // 820 Wh // 160/150 mm // 29/27.5 inch // 21.6 kg // 11490 Euro.

The facts about the Rotwild R.EX Ultra

  • Motor: Shimano EP801, 85 Nm max. torque
  • Battery: 820 Wh (removable)
  • Frame material: Carbon
  • Suspension travel: 160/150 mm
  • Wheel size: 29/27.5 inch (Mullet)
  • Frame sizes: S, M, L, XL
  • Price: 11,490 euros
  • Weight: 21.6 kg (test bike in size L, EMTB measurement)
  • Permissible total weight: 130 (manufacturer's specification)
  • Manufacturer's warranty: 5 years
  • Special features: Quick-release battery with carbon outer shell

The Shimano EP801 in the Rotwild

Since the update to the Shimano EP801, the Japanese drive delivers even more peak power, making it one of the lightest and most powerful drives on the market. The special feature of the Shimano: the motor releases its full power even when the rider pedals moderately. This means you can shoot up easy forest road climbs particularly quickly.

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The Shimano EP801 is the lightest drivetrain in the 85 Newton metre class and still delivers high peak performance. In terms of modulation, some competitors are now ahead of it.Photo: Max FuchsThe Shimano EP801 is the lightest drivetrain in the 85 Newton metre class and still delivers high peak performance. In terms of modulation, some competitors are now ahead of it.

On technical trails, however, it sometimes lacks acceleration before key sections. In addition, the Shimano motor is not very stable at speed and rattles downhill. New: Thanks to the new race software the Shimano can be adjusted more to the rider's personal preferences. A caster can also be selected here. This helps the Rotwild to overcome technical obstacles and uphill steps more easily.

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>> In the test: The Shimano EP801 in the lab and in practice

In the R.EX, Rotwild relies on a battery specially developed for the bike with a whopping 820 watt hours. Thanks to the carbon outer casing, the battery is super light at just 3.65 kilograms. For comparison: Bosch's 800 weighs four kilograms, the 750 even weighed 4.35 kilograms. The battery on the Rotwild is also very easy to remove from the bike. Charging the battery away from the bike is therefore no problem at all.

The Rotwild battery simply folds out to the side at the touch of a button. This is one of the best solutions on the market and makes off-bike charging or battery replacement particularly easy.Photo: Max FuchsThe Rotwild battery simply folds out to the side at the touch of a button. This is one of the best solutions on the market and makes off-bike charging or battery replacement particularly easy.

The geometry

In addition to its super-low weight, the Rotwild has extremely short chainstays. So the absolute trail rocket? Not quite. Because the low front and the seat post with a lot of setback significantly defuse the actually successful geometry values. As a result, the dimensions are more suited to sporty flatland tours than nasty all-mountain terrain. Nevertheless, since the geometry is actually modern, the R.EX can easily be made a little more potent with other components. Only the long seat tube cannot be changed and has to fit the rider's size.

EMTB measurements at a glance (frame size L)

  • Seat tube length: 468 mm
  • Wheelbase: 1260 mm
  • Reach: 489 mm
  • Stack: 633 mm
  • Steering angle: 64 degrees
  • Seat angle: 76.7 degrees
  • Chainstay length: 436 mm
The seat tube is long. The actually long Eightpins seatpost can only utilise its advantages to a limited extent. A strong setback also flattens the seat angle uncomfortably and, in combination with the low front end, makes for a stretched riding position uphill.Photo: Max FuchsThe seat tube is long. The actually long Eightpins seatpost can only utilise its advantages to a limited extent. A strong setback also flattens the seat angle uncomfortably and, in combination with the low front end, makes for a stretched riding position uphill.

The equipment of the Rotwild R.EX Ultra

The top-of-the-range Ultra model comes with particularly sophisticated equipment. Fox Factory suspension, carbon wheels and XT Di2 gears leave nothing to be desired. In our equipment rating, this results in real top values.

  • Fork / shock: Fox 36 Factory GripX / Float X Factory
  • Gear system: Shimano XT Di2 (12-speed)
  • Brakes: Shimano XT
  • Wheels: Crankbrothers Synthesis Enduro Carbon
  • Tyres: Schwalbe Magic Mary Superground, Hans Dampf Supertrail; 29 x 2.4 / 27.5 x 2.6

Practical test: How the Rotwild R.EX Ultra rides

We are therefore excited to start the uphill with the lightweight speedster. In Boost mode, the Shimano unleashes its full power even with a gentle pedal stroke. The competition has to stretch a little to keep up on the forest road. A whopping 16.6 km/h average in the range test speaks for itself.

Traction at the rear is good, but in terms of modulation, the Japanese motor has lagged noticeably behind its main competitor since the update to the new CX. The stretched riding position and short chainstays also make it difficult to control the R.EX on demanding climbs. The typical Rotwild seatpost with its strong setback is primarily to blame. This is supposed to take the strain off your wrists on flat terrain. In our eyes, however, this is outdated for such a modern bike.

With the Shimano EP801 and low weight, the Rotwild R.EX outpaces many a rival, especially when pedalling gently on tours.Photo: Max FuchsWith the Shimano EP801 and low weight, the Rotwild R.EX outpaces many a rival, especially when pedalling gently on tours.The strong seatpost setback and short chainstays make the Rotwild a little challenging to ride uphill.Photo: Max FuchsThe strong seatpost setback and short chainstays make the Rotwild a little challenging to ride uphill.

Light on its feet! But also strong downhill?

Unfortunately, we also noticed a few small things on the downhill that have often bothered us on Hessian bikes. The seat tube is too long, so the powerful Eightpins dropper post can't really play to its advantage. With flat handlebars, few spacers and a short head tube, the front end is unusually low for a bike in this travel class. As a result, you don't feel optimally integrated into the bike on descents. None of the testers were able to find a good riding position straight away.

On flatter trails, the Rotwild is in its element and shines with lively and light-footed handling.Photo: Max FuchsOn flatter trails, the Rotwild is in its element and shines with lively and light-footed handling.In demanding terrain, the pilot must know what he is doing. The Rotwild reacts a little bitchily to riding errors. There is also room for improvement in the rear suspension and riding position.Photo: Max FuchsIn demanding terrain, the pilot must know what he is doing. The Rotwild reacts a little bitchily to riding errors. There is also room for improvement in the rear suspension and riding position.

Strong on the other hand: The low (wheel) weight and short chainstays give the R.EX agile handling. The bike is in its element on flat and winding trails. It's a lot of fun to ride! Unfortunately, the rear suspension offers a little less counter-pressure even with a firm setup. The big brother R.EXC is in a different league here. If the downhill trails become steeper and more demanding, there is no real riding confidence. The low front end and the chassis, which feels stiff, often cause riding errors with a noticeable loss of direction. It's a shame that the Rotwild rattles much more on the descents than we would like from a bike in this price range.

Seat position, reach height and service friendliness at a glance: For the reach height, the black arrow shows the altitude metres with unthrottled assistance, the grey arrow shows the additional altitude metres on the last few percent in a throttled emergency mode.Photo: BIKE TestabteilungSeat position, reach height and service friendliness at a glance: For the reach height, the black arrow shows the altitude metres with unthrottled assistance, the grey arrow shows the additional altitude metres on the last few percent in a throttled emergency mode.

BIKE review of the Rotwild R.EX Ultra (E-MTB)

Strengths

  • Low weight
  • Top battery removal
  • Light on your feet on flat trails

Weaknesses

  • Geometry not balanced
  • Rear triangle releases suspension travel too easily
  • Too quickly overwhelmed in difficult terrain
Strong equipment and good range: For an all-mountain bike with top parts, however, the downhill performance could be significantly better.Photo: BIKE TestabteilungStrong equipment and good range: For an all-mountain bike with top parts, however, the downhill performance could be significantly better.

BIKE review of the Rotwild R.EX Ultra

The Rotwild R.EX Ultra shines with top equipment, high-quality chassis and super-low weight despite a lot of motor power and practical battery removal. On flatter trails, the bike is lively and direct, but lacks reserves on steep descents. This makes the bike more of a fast tourer than a true all-mountain pro. Overall, the geometry and suspension didn't seem quite balanced to us. - Adrian Kaether, BIKE Editor for Test & Technology
Adrian Kaether is test editor at BIKE.Photo: Georg GrieshaberAdrian Kaether is test editor at BIKE.
Adrian Kaether

Adrian Kaether's favourite thing to do is ride mountain bikes on bumpy enduro trails. The tech expert and bike tester knows all about Newton metres and watt hours, high and low-speed damping. As test manager at MYBIKE, Adrian also likes to think outside the box and tests cargo bikes and step-through bikes as well as the latest (e-)MTBs.

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