Shimano to Rohloff put to the test: Do e-bikes need different gear systems?

BIKE's take on e-bike gear systems

The short answer is: yes, e-bikes need different gear systems. Due to the high load on the chain, standard bicycle gear systems can be ready for the scrap heap after just a few hundred kilometres. Gear systems specially optimised for e-bikes (Shimano Linkglide, SRAM Transmission) and low-maintenance derailleurs perform significantly better. You should steer clear of the combination of a powerful mid-drive motor and a traditional Hyperglide groupset such as Deore or XT!

It’s a familiar scenario for many cyclists: you pop your bike in for a quick service and, before you know it, you’re out several hundred euros. The bike shop tells you the chain and cassette need replacing. The customer is baffled: ‘But it’s got a good XT groupset on it, and besides, the bike’s only done a few hundred kilometres!’ Discontent is inevitable, as BIKE reported.

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The hard truth is that both sides may be right. The bike shop correctly identified the wear and tear and replaced the parts as required, although the customer is also right in saying that high-quality components were fitted in the first place. There are many possible causes, and riding without shifting gears properly can play a part. However, from our long-term e-bike tests we know that even riders who shift gears correctly can quickly push delicate drivetrains to their wear limits.

Many manufacturers fit the wrong circuits

The problem is that e-bikes are often fitted with gear systems that aren’t actually designed for them. After all, a wide range of gears, a crisp shifting feel and a light weight are clear selling points. SRAM’s first proper e-bike drivetrain, the EX1, with just eight gears (reviewed here) was therefore a complete flop, despite its high fatigue strength.

However, gear manufacturers have since adapted and now offer special e-bike gear systems that also feature a wide range of gears. Shimano’s Linkglide system, which is primarily used on Cues, features more robust components and shifts deliberately more slowly to significantly increase the gear system’s durability. Our favourite is SRAM’s Direct Mount Transmission series, which shifts particularly smoothly even under heavy load on the chain.

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The special case of the in-hub motor

However, the location of the motor is also crucial. Many city bikes and e-gravel bikes use hub motors in the rear wheel. In this case, the motor’s power is transmitted directly to the rear wheel. The drivetrain is subjected only to the rider’s pedalling force. In this case, you can safely opt for conventional lightweight gear systems such as Shimano’s Hyperglide (GRX, XT and the like). They engage slightly faster and save weight.

The situation is different with mid-frame motors, such as the Bosch CX and PX models. Here, the full motor power is transmitted to the rear wheel via a chain or belt, alongside the rider’s pedalling effort. Anyone who has ever tried to change gears on an e-bike like this under full load knows what that can lead to. Anything is possible, right up to a broken chain. For e-bikes with a mid-drive motor, we therefore recommend special e-bike gear systems that can cope with the motor’s high power output.

And what about gear changes?

Most gear systems are equally well suited to e-bikes. The reason is that, as a rule, gear changes are not made under load in this context. This prevents excessive wear and tear. Furthermore, belts or chains always run perfectly in line, rather than at a significant angle as is the case with derailleur systems. Rohloff, Nexus, Pinion, 3x3 and the like are therefore a good and durable option, even on e-bikes. The downside is the often higher price.

These circuits are fully compatible with e-bikes

• Shimano Linkglide: All Cues models, Linkglide versions of Deore and XT (note: rare)
• Shimano hub gears: Nexus and others in their electric versions
• SRAM drivetrain: Eagle 70, Eagle 90, S1000, GX, XO, XX – the T-Type versions with direct mount
• Manual gearbox: Rohloff, Pinion, 3x3 and others

We would not (!) recommend these circuits for e-bikes

• Shimano Hyperglide: Deore, XT, GRX – not even the new versions with Hyperglide+
• SRAM non-T-Type: SX, NX, GX, XO, XX – the older versions without direct mount

E-bike gear systems: pros and cons

Strengths

• Smoother gear changes, even with a load on the chain
• Longer service life, especially for e-bikes
• Comparable in price to traditional circuits

Weaknesses

• A few less gears and a bit more weight