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KMC Z7 Chain (6/7/8-Speed)

Name: KMC Z7 Chain (6/7/8-Speed)
Brand: KMC

The KMC Z7 (formerly labeled Z51) is the standard replacement chain for 6-, 7- and 8-speed drivetrains, which covers most hub-motor e-bikes. It is an inexpensive chain that includes a reusable quick link, so installation needs only a chain breaker to size it. On an e-bike the chain carries only your pedaling load with a hub motor, so a basic chain like this lasts well; with a mid-drive you should step up to an e-bike-rated chain. Measure your old chain for length and replace the freewheel if the old chain was badly worn.

7-speed hub-motor e-bikesBudget drivetrain refreshesRiders who want a quick-link install

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Key considerations

Count your rear cogs: Z7 is for 6/7/8 speed only
Size to the old chain or by the big-big method
Replace freewheel/cassette if the old chain was stretched past 0.75%
Includes a quick link; keep a spare on the bike

Pros

Cheap and widely available
Quick link included
Adequate for hub-motor loads

Considerations

Not rated for mid-drive torque
Basic corrosion resistance

Features & specifications

Speeds	6/7/8

Specifications are manufacturer-published figures or our own notes; confirm on the current listing before purchase.

Compatibility notes

6, 7 and 8-speed derailleur drivetrains; hub-motor e-bikes — for mid-drives choose an e-bike-rated chain

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Similar alternatives

All e-bike chains →

FreewheelsFeatured

Shimano MF-TZ500 7-Speed Freewheel 14-28T

Most rear hub-motor e-bikes use a thread-on freewheel rather than a cassette, and the 7-speed Shimano MF-TZ500 (successor to the TZ-31) is the one that comes on a huge share of them. It screws onto the motor's threaded boss and comes off with a standard Shimano freewheel remover. The 14-28 range is conservative: fine for flat commuting and assisted riding, limiting if you want to pedal fast downhill. When the freewheel starts skipping or the pawls stick, replacing it is a cheap twenty-minute job if you have the tool.

Best for: 7-speed hub-motor e-bikes with a thread-on freewheel · Fixing a skipping or sticky freewheel · Like-for-like replacements

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E-Bike Chains

KMC e8 E-Bike Chain (8-Speed)

KMC's e-series chains are built for the extra torque a mid-drive motor puts through the drivetrain, with thicker, stronger plates and pins than a standard chain of the same speed. The e8 is the 8-speed version and also works on most 7-speed systems with 7-speed cog spacing. If you have a Bafang BBS02, BBSHD or a production mid-drive bike (Bosch, Shimano STEPS, Bafang M-series) with an 8-speed cassette, this is the chain to buy when the old one measures worn. It will not make a hub-motor bike faster, but it will not hurt either.

Best for: Mid-drive e-bikes with 8-speed cassettes · BBS02/BBSHD conversions · Heavy riders who break standard chains

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Derailleurs

Shimano Tourney RD-TY300 6/7-Speed Rear Derailleur

The Tourney TY300 is the derailleur on an enormous number of 7-speed e-bikes, and it is what you buy when the original gets bent by a fall or a stick. It is cheap, easy to set up, and available in a few mounting styles: a direct-mount version with a bracket (claw) for bikes without a hanger and a standard-hanger version. Before ordering, look at how your old derailleur attaches. It shifts fine for a 7-speed hub-motor bike and pairs with the stock thumb or trigger shifters; just expect to replace the cable at the same time.

Best for: 7-speed hub-motor e-bikes with a bent or broken derailleur · Budget like-for-like replacements · Riders who want a part that matches the stock shifter

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