An aluminium replacement for the BBSHD's stock ring in two forms: a 42-tooth ring with a deep 20.5mm offset that pulls the chainline inboard on regular frames, and a 32–38 tooth fat-bike ring with an 8mm offset. Both use narrow-wide teeth to keep the chain on over rough ground.
The BBSHD bolts on where the old crankset was, but its stock chainring sits well outboard of where a bicycle's chainring would. On a regular 68–73mm bottom bracket, that pushes the chain line out toward the small cogs. In the big cogs the chain runs at a steep angle, grinds, and on rough ground it can walk off entirely.
CHAOZHU's 42T ring answers that with a 20.5mm offset. The teeth sit much closer to the frame than a flat ring would, pulling the chain in toward the middle of the cassette. That straighter line matters most in the gears you use for climbing, where the motor is pushing hardest.
Offset figures are not measured the same way by every maker, and frame shapes vary. The only reliable test is your own bike: shift to the largest and smallest cogs and look at the chain angle from behind. Measuring chainline, and offset rings side by side, are both in the BBSHD chainring guide.
The positive/negative tooth profile does the rest. Alternating wide and narrow teeth match the chain's inner and outer plates, which grips the chain better than a plain ring on a bike without a front derailleur.
| Spec | Value |
|---|---|
| Brand | CHAOZHU |
| Motor fit | Bafang (8FUN) BBSHD 48V/52V 1000W |
| Tooth count | 42T; fat-bike version in 32T, 34T, 36T, 38T |
| Offset | 20.5mm on the 42T; 8mm on the fat-bike version |
| Tooth profile | Positive/negative (narrow-wide) teeth |
| Chain compatibility | 6 to 11 speed |
| Material | 6061-T6 aluminium alloy |
| Finish options | Black, blue, red |
| Weight | 177 g (42T) |
| Fat-bike version fit | BBSHD and M625 mid-drives |
| Model name | Chain Ring 42T |
| Mounting | Bolts to the BBSHD drive in place of the stock ring |
| Included | Chainring |
Most BBSHD kits ship with a larger ring, commonly 44 or 46 teeth. That gearing is fine for fast road commuting, but on steep trails it leaves the motor lugging at low revs. A BBSHD pulling hard at low revs makes more heat and less power, which is exactly the condition that cooks controllers on long climbs.
Going to 42T gears the whole bike down. The motor spins faster for any given road speed, which keeps it in a more efficient range when the grade kicks up. Top speed drops a little in the smallest cog, which few trail riders miss.
| Ring | Ratio on 11T cog | Ratio on 42T cog | Change vs 46T |
|---|---|---|---|
| 46T | 4.18 | 1.10 | — |
| 44T | 4.00 | 1.05 | 4% lower |
| 42T | 3.82 | 1.00 | 9% lower |
| 36T | 3.27 | 0.86 | 22% lower |
A 9% drop is noticeable but not dramatic. It suits a rider who mixes road miles to the trailhead with climbing once there. If the rides are mostly steep singletrack, cargo hauling or towing, the smaller rings in the fat-bike version, or a 32–38T ring from another maker, go further.
At 177 g, the ring is light enough that weight is not a reason to choose it or avoid it. Gearing and chainline are what count.
The second CHAOZHU ring is a different part for a different bike. It comes in 32, 34, 36 and 38 teeth with an 8mm offset, and it is made to fit the BBSHD and Bafang's M625 on fat bikes. The shallower offset is deliberate: a fat bike's rear hub is much wider, so its cassette sits further out and needs the chain further out too.
Put the 42T's deep 20.5mm offset on a fat bike and the chain would angle inward to a cassette that sits outboard, causing the very rub it was meant to cure. The 8mm version keeps the chainline where a wide-hub bike needs it while still offering small, climbing-friendly sizes.
Fat bikes often use 100mm or 120mm bottom brackets, and the BBSHD fits both with the right mounting. The chainline on these frames depends on shell width, hub spacing and the tire's clearance at the chainstay, so check the ring against your own frame before a long ride. Shell widths and matching offsets for snow and sand frames sit in the BBSHD fat bike guide.
Small rings also help heat. A heavy fat bike on soft ground is one of the hardest loads a BBSHD sees, and a 32T or 34T ring lets the motor spin up instead of grinding at low revs.
CHAOZHU builds its rings from 6061-T6 aluminium. That makes them light and corrosion-resistant, but aluminium teeth wear faster than steel under a 1000W motor, especially with a dirty chain. Two other BBSHD rings take different approaches; pick by how you ride and how often you are willing to swap parts.
Pick CHAOZHU if chainline is your main problem on a regular frame, you want 42 teeth, and you prefer a clean, light ring in black, blue or red. Pick steel if you ride mostly cargo or winter commutes and would rather replace a ring rarely. Pick the Powallon if you ride in street clothes and want a guard.
Four checks settle whether it suits your bike:
Keep the chain clean and replace it before it stretches. A worn chain on an aluminium ring wears the teeth quickly, and the narrow-wide profile loses its grip when the teeth hook.
Order the BBSHD version for a BBSHD. BBS01 and BBS02 motors use a different chainring mount, so a BBSHD ring will not bolt on.
It moves the teeth inboard toward the frame, pulling the chainline toward the middle of the cassette on regular 68–73mm bottom brackets. That reduces chain angle, noise and drops in the low gears.
The 32–38T ring with the 8mm offset. Fat bikes have wider rear hubs, so the chain needs to sit further out than the 42T's deep offset allows.
CHAOZHU lists 6 to 11-speed chain compatibility. For 12-speed, pick a ring rated for it.
Against a 46T ring, a 42T is about 9% lower in every gear. Against a 44T, about 4% lower.
