Light eMTB meets motor power. With the R.X375 ULTRA, ROTWILD combine a powerful Shimano EP8 motor with a small 375 Wh battery, bringing together things that don’t belong together – until now. But can the super-light bike hold its own against the competition without running out of juice?

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For an overview of the test fleet head to the group test: The best eMTB of 2021 – 25 models in review

ROTWILD R.X375 ULTRA | Shimano EP8/375 Wh | 150/150 mm (f/r)
18.80 kg in size L | € 11,499 | Manufacturer’s website

Powerful motor, small battery. With the R.X375 ULTRA, ROTWILD deliberately buck the current trend of big batteries. They wanted to create a sporty trail eMTB that can replicate the agile handling of Light eMTBs and still provide ample motor power when required. The 85 Nm Shimano EP8 motor is the ideal basis for this concept. This is paired with a compact 375 Wh battery which can be removed from the side of the down tube within seconds. Several riding profiles and finely-tuned motor settings increase efficiency and thus allow for a relatively large range with reduced motor power. However, we prefered taking the R.X375 ULTRA for fast-paced evening laps on our local trails with full motor support. The drive system is neatly integrated into the elegant, lightweight carbon frame, which rolls on big 29” wheels. Other details such as the soft chainstay protector and clever cable routing that prevents the cables from rattling inside the frame, testify to the high quality standards of the brand.

The spec of the ROTWILD R.X375 ULTRA

ROTWILD rely on lightweight construction not only for the frame and battery but also for the spec of the € 11,499 R.X375 ULTRA. If it says XTR, you’ll get XTR: unlike many other manufacturers in this test, ROTWILD didn’t try to save a few pennies by throwing cheaper components into the mix! Only the small 180 mm rear brake rotor doesn’t fit the otherwise rosy picture. However, overzealous weight tuning can quickly become a problem: the thin casings of the Schwalbe Nobby Nic tires combined with the DT Swiss HXC 1200 SPLINE carbon wheelset could be a recipe for disaster. If you decide to run this combo, you better prepare yourself to deal with pinch flats and poor grip. That’s why ROTWILD delivered our test bike with a Magic Mary/Hans Dampf combo in the more robust Super Trail casing – they know us! Fast, aggressive riders should consider an even burlier rear tire with the bombproof Super Gravity casing. The supportive 150 mm FOX Factory suspension combines a DPS shock and 36 FIT4 fork. For the latter, we’d happily trade the lockout for the superior GRIP2 damper.

What a cockpit
ROTWILD rely exclusively on Shimano components. The I-Spec standard allows them to combine excellent ergonomics with a clean look. The clever cable management, where all EP8 cables run straight from the stem into the frame, rounds off the outstanding integration.
Small battery, top riding fun
The small, light 375 Wh battery gives the R.X375 ULTRA its great handling. The quick release system allows for super-fast battery changes but the elongated shape of the battery makes it hard to carry a spare in your backpack.
Problem area
The R.X375 comes equipped with shallow-profiled Schwalbe Nobby Nic tires in the thin Super Ground casing. For better grip and increased puncture protection, ROTWILD delivered our test bike with a Magic Mary/Hans Dampf combo in the Super Trail casing: your dealer should do the same!
Exemplary function with braking issues
Rotwild’s integration of the entire Shimano EP8 drive system is exemplary: inconspicuous, quiet, failsafe and ergonomic. Even the magnet of the speed sensor is neatly integrated into the 180 mm rear brake rotor. Unfortunately, the rotor is too small for how the ROTWILD will be ridden.

ROTWILD R.X375 ULTRA

€ 11,499

Specifications

Motor Shimano EP8 85 Nm
Battery IPU375 QR CARBON 375 Wh
Display Shimano EP800
Fork FOX 36 Factory FIT4 150 mm
Rear Shock FOX DPS Factory 150 mm
Seatpost EightPins NGS 2 individuell bis 230 mm
Brakes Shimano XTR M9120 200/180 mm
Drivetrain Shimano XTR 1x12 TBC
Stem ROTWILD S140 50 mm
Handlebar ROTWILD B220 Carbon 780 mm
Wheelset DT Swiss HXC1200 SPLINE 29"
Tires Schwalbe Magic Mary/Hans Dampf Super Ground 2.35"

Technical Data

Size S M L XL
Weight 18.80 kg
Perm. total weight 120 kg
Max. payload (rider/equipment) 101 kg
Trailer approval no
Kickstand mount yes


Integration doesn’t stop at the motor
While all other bikes on test rely on a pipe sliding inside another pipe, ROTWILD use a fully integrated Eightpins dropper. With adjustable travel of up to 230 mm, it allows riders of all sizes to have maximum freedom of movement, even with long seat tubes.
Very stiff
The R.X375 ULTRA has amongst the firmest and sportiest suspension in the test. While at slow speeds and with a passive riding style it offers little comfort and poor traction, an aggressive riding style and good skills will be rewarded with massive support and endless reserves.
Quiet as a mouse
The soft, ribbed chainstay protector is just one of many elaborate details on the ROTWILD frame. As a result, downhill the R.X375 ULTRA is quiet as a mouse, except for the typical rattling of the EP8 motor.

All our test riders measure around 1.85 m tall and felt immediately comfortable with the 475 mm (size L) reach. At 470 mm (size L), the seat tube is relatively long. Nevertheless, the EightPins seatpost lets you adjust the stroke and maximum extension of the dropper and adapt it to your needs. On the flats, the pedalling position is sporty. The steep seat tube angle positions the rider centrally on the bike but also creates a fair amount of pressure on your hands. Therefore, the R.X375 Ultra prefers riding up and down the hill rather than ambling around the lake.

Size S M L XL
Seat tube 410 mm 440 mm 470 mm 506 mm
Top tube 590 mm 610 mm 640 mm 667 mm
Head tube 110 mm 110 mm 130 mm 140 mm
Head angle 66.5° 66.5° 66.5° 66.5°
Seat angle 75.5° 75.5° 75.5° 75.5°
Chainstays 450 mm 450 mm 450 mm 450 mm
BB Drop 30 mm 30 mm 30 mm 30 mm
Wheelbase 1,184 mm 1,205 mm 1,237 mm 1,266 mm
Reach 430 mm 450 mm 475 mm 500 mm
Stack 618 mm 620 mm 636 mm 645 mm
Helmet SCOTT Vivo Plus | Glasses SCOTT Shield | Shorts SCOTT Trail vertic
Shoes Five Ten Kestrel Lace | Socks SCOTT Performance Crew | Gloves SCOTT Ridance

The ROTWILD R.X375 ULTRA on the trail

On flowing uphills, no other bike in this test was as much fun as the R.X375 ULTRA. While the battery might well run out of juice sooner, none of the Rotwild’s competitors managed to combine this much power with such lively handling. Here the approach is ‘drift into the corner and blast out of it on one wheel’ – and that’s UPHILL! Thanks to its supportive, efficient suspension and low weight, the ROTWILD feels more powerful than any other Shimano bike in this test. That being said, on technical terrain, it struggles to keep up with the strongest climbers in the test. On steep ramps, the R.X375 requires great physical effort to keep the front wheel tracking, while on loose terrain the supportive suspension and even the upgraded tires fail to generate enough traction.

On the trail, the concept of the small battery pays off: top riding fun for a short time!

Tuning tips: upgrade the tires to a more robust and grippier model immediately | bigger 200 mm rotor at the rear (make sure you get the version with a sensor magnet: RT-EM910)

Downhill, we get the same feeling as on the climbs. The R.X375 ULTRA combines the best of two worlds: it’s just as agile and nimble as an analogue trail bike, yet still as powerful as the most genuine all-rounders on test. With its supportive suspension and sporty handling, it feels in its element on flowing trails with jumps, berms and rollers. Regardless of your riding skills, the ROTWILD implements direction changes and spontaneous manoeuvres quickly and playfully – manuals, jumps and wheelies are lots of fun! However, on technical and winding trails, it demands good riding skills and attention. If you fail to spot your line and hesitate over obstacles, it will punish you with poor traction and considerable understeer. Aggressive riders who actively weight the front wheel in wide corners and prefer to gap trail obstacles rather than riding over them will have a blast onboard the R.X375 Ultra. Even on fast bike park tracks, you’re in good hands, because the supportive rear of the ROTWILD always offers sufficient reserves, dealing even with bigger hits without breaking a sweat. Only the fork forces you to pull the brakes sooner than with the more downhill-oriented bikes in the test.

Riding Characteristics

7

Agility

  1. sluggish
  2. playful

Stability

  1. nervous
  2. stable

Handling

  1. demanding
  2. balanced

Riding fun

  1. boring
  2. lively

Motor feeling

  1. digital
  2. natural

Motor power

  1. weak
  2. strong

Value for money

  1. poor
  2. top

Application

Forest road

1

Flow trail uphill

2

Flow trail downhill

3

Technical single trail uphill

4

Technical single trail downhill

5

Downhill tracks

6

Conclusion

The special battery concept of the elegant R.X375 ULTRA really works, allowing ROTWILD to combine the agile character and low weight of an analogue trail bike with the outstanding climbing qualities of powerful eMTB all-rounders. Aggressive and skilled riders will be able to push the R.X375 to the limit and have shed-loads of fun in the process. However, for beginners and touring riders, the bike is only suitable to a limited extent. While integration is exemplary, ROTWILD have taken the weight optimisation a little too far.

Tops

  • extravagant look
  • overall concept perfectly implemented
  • exemplary EP8 integration
  • very fast and agile

Flops

  • spec fails to match the area of application
  • no range extender, a spare battery is unwieldy long
  • requires active riding style

You can find out more about at rotwild.com

The test field

For an overview of the test fleet head to the group test: The best eMTB of 2021 – 25 models in review

All bikes in test: Cannondale Moterra Neo Carbon 1 (Click for review) | Canyon Spectral:ON CF 9 (Click for review) | CENTURION No Pogo F3600i (Click for review) | CUBE Stereo Hybrid 140 HPC SLT Nyon (Click for review) | CUBE Stereo Hybrid 160 C:62 SLT Kiox (Click for review) | Ducati TK-01 RR (Click for review) | FLYER Uproc6 9.50 (Click for review) | FOCUS JAM² 6.9 NINE (Click for review) | GIANT Trance X E+ 1 (Click for review) | Haibike AllMtn 7 (Click for review) | KTM Macina Kapoho Prestige (Click for review) | Lapierre Overvolt GLP 2 Team (Click for review) | MERIDA eONE-SIXTY 10K (Click for review) | Mondraker Crafty Carbon XR (Click for review) | Moustache Samedi 29 Trail 8 (Click for review) | ROTWILD R.X375 ULTRA | Santa Cruz Bullit X01 RSV Air (Click for review) | SCOTT Ransom eRIDE 910 (Click for review) | SIMPLON Rapcon PMAX (Click for review) | Specialized S-Works Turbo Levo (Click for review) | Specialized S-Works Turbo Levo SL (Click for review) | STEVENS E-Inception AM 9.7 GTF (Click for review) | Thömus Lightrider E2 Pro (Click for review) | Trek Rail 9.9 X01 (Click for review) | Whyte E-150 RS 29ER V1 (Click for review)


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Words: Felix Stix Photos: Various

About the author

Felix Stix

Felix is chief of testing and undoubtedly one of the best test riders in the world. With a degree in sports engineering, excellent mountain bike skills, his love of technology and as a certified bike guide, Felix has everything it takes to make comprehensive and fair assessments of bikes. His legendary group tests are internationally known and feared, though they tend to be a bit longer due to his love of detail and technical deep dives. Every year, he reviews around 100 bikes, specialising in the subject of tires, motors and suspension, before putting on his skis come winter! His know-how is incorporated into each of our reviews, ensuring the quality of our work stays high!