Schlumpf High Speed Drive: 2-Speed Gearing for E-Bikes

On a high-power e-bike, gearing is everything. Make too much torque in the wrong gear and you either spin out at speed or bog down on a climb. The Schlumpf High Speed Drive solves that problem elegantly by building a two-speed gearbox directly into the bottom bracket — effectively doubling your gear range without adding a single cog. Here's how it works and why it's such a natural fit for powerful builds.

What is a Schlumpf drive?

Schlumpf is a Swiss-engineered planetary gearbox that lives inside the crank spindle. With a tap of your heel on a button at the end of the crank axle, you shift between two internal ratios: a direct 1:1 drive and an overdrive (or underdrive, depending on the model). It's essentially a second transmission hidden where your cranks already are — no extra derailleur, no extra chain.

The High Speed Drive provides a 1.65x overdrive, letting you keep pedaling productively at higher speeds instead of spinning uselessly once the bike is moving quickly.

Why it matters on a high-power e-bike

Powerful e-bikes have a wide operating window — from crawling up technical climbs to cruising at high speed. A conventional cassette can struggle to cover both ends well. The Schlumpf drive effectively multiplies your existing gearing:

• Direct mode keeps your normal gearing for climbing and technical terrain, where you want torque and control.
• Overdrive mode raises your top gear so you can continue contributing power at speed rather than pedaling air.

The result is a usable pedaling cadence across a far broader speed range — exactly what a torquey, fast e-bike needs.

Clean, durable, and low-maintenance

Because the gearbox is sealed inside the bottom bracket, it's protected from mud, water, and impacts — a real advantage over exposed derailleur setups on aggressive off-road bikes. There's no extra chain to manage and shifting works whether you're pedaling hard, coasting, or even stopped, which is genuinely useful in stop-and-go or technical situations.

Pairing the Schlumpf with an HPC build

A high-speed gearbox only shines when it's matched to the right crankset and a bike that can use the range. Our cranksets and crank arms are chosen to complement high-power drivetrains, and models across the Revolution lineup are built to take full advantage of wide-range gearing at speed. On the pedal-forward side, a bike like the Trailblazer benefits from broad gearing for everything from steep enduro climbs to fast fire-road descents.

You can learn more about the gearbox itself directly from the manufacturer at Schlumpf.

Is a 2-speed drive right for you?

If you ride terrain that swings between steep, technical climbs and high-speed sections — and you want to keep pedaling meaningfully at both ends — a Schlumpf High Speed Drive is one of the cleanest ways to widen your range. It adds mechanical simplicity where a bigger cassette or a second derailleur would add clutter.

Explore HPC cranksets and 2-speed drives to dial in the gearing on your next high-power build.