Rivian's TM-B electric bike

Original Article ↗ Hacker News Discussion ↗

Design & Feature Set

  • Many like the idea of a premium, full‑suspension commuter / cargo e-bike with modular top frame, swappable accessories, and a well‑designed battery system (swappable packs, USB‑C charging, some pack-level utility power).
  • Others say it feels like a car-company fantasy bike: lots of tech (touchscreen, NFC lock, GPS, app integration, smart helmet with speakers) layered onto something that “looks like what non‑cyclists think a good bike is.”

Pedal‑by‑Wire Drivetrain & Regeneration

  • The “pedal‑by‑wire” system (pedals drive a generator, not the wheel) is the most controversial aspect.
  • Supporters see potential for:
    • More comfortable, constant pedaling cadence independent of speed.
    • Rich software control (programmable resistance, power curves, stationary/exercise-bike mode).
  • Critics argue:
    • It throws away the key advantage of bicycles: ultra‑efficient, simple mechanical drivetrains.
    • Efficiency losses (generator → battery → motor) and lack of a mechanical fallback mean if electronics fail or battery is flat, the “bike” is effectively dead weight.
    • Pedals appear largely regulatory (to qualify as an e-bike rather than a moped) rather than functional.
  • Regen braking is seen by some as nice for pad wear and modest range extension; others call it pointless complexity on such a light vehicle.

Brakes, Controls & Safety

  • Broad agreement that hydraulic disc brakes are appropriate and near “table stakes” for a heavy, powerful e-bike.
  • Debate over touchscreens and full-touch controls: some see them as fragile, distracting, and unreliable in rain; others note such consoles are already common on e-bikes.
  • The connected helmet with audio and noise cancellation worries riders who already feel vulnerable in mixed traffic.

Price, Market & Comparisons

  • $4,500 polarizes the thread. Defenders compare it to high-end Bosch-equipped or cargo e-bikes; detractors compare it to cheaper Chinese e-bikes, DIY conversions, or even small electric motorcycles with more power.
  • Many doubt the styling and spec justify the price; others think there is already a proven $4k+ e-bike segment it can slot into.

Weight, Range & Performance Skepticism

  • The claimed ~800 Wh / 100-mile range is widely viewed as optimistic except at low speeds with substantial pedaling.
  • Rivian’s omission of weight in specs is read as a red flag; commenters expect 80–100 lb and warn that such mass is unmanageable for apartment dwellers and unpleasant to pedal unassisted.
  • Some question whether a 750 W–class system with pedal‑by‑wire will handle very steep hills as well as a traditional mid‑drive where human power adds directly to the wheel.

Regulation, Legality & “Is It a Bike?”

  • Discussion around US Class 1/2/3 rules, top speeds, and throttles; some confusion over whether Class 3 can legally include a 20 mph throttle plus 28 mph pedal assist.
  • Several note the pedals seem primarily there to stay in e‑bike regulatory categories (bike lanes, no license/insurance) despite motorcycle-like behavior.
  • Concerns that fast, heavy “e-bikes” are increasingly de facto low‑speed motorcycles, raising conflict with pedestrians and traditional cyclists.

Repairability & Proprietary Systems

  • Many prefer e-bikes from traditional bicycle makers using mostly standard parts (Bosch/Bafang mid‑drives, common brakes, wheels, chains) for serviceability and parts availability.
  • Rivian’s highly integrated, proprietary drivetrain and electronics raise worries about long‑term maintenance, firmware/DRM lock‑in, and what happens if the company discontinues support.

Micromobility Context & Use Cases

  • Some are genuinely excited to see more serious micromobility options, including the cargo “quad” and modular kid/cargo setups.
  • Others think car makers consistently overcomplicate e‑bikes and ignore the virtues of simple, lightweight, easily repairable bicycles.
  • Safety and infrastructure are recurring themes: without better protected bike lanes and clearer rules for fast e‑bikes, several expect more regulation, restrictions on trails, and possible licensing requirements.