mGYDY BBSHD Chainring

Offset, or dish, is the distance between the ring's mounting face and its teeth. Fat bike rings often use a shallow dish, around 8 mm, to keep the chain outboard for wide rear ends. Deep-dish rings of 20 mm or more pull the chain well inboard for narrow frames. A 12 mm ring sits between those two families.

That middle depth is useful because the stock BBSHD ring lands outboard on many standard frames. A moderate offset can bring the chain closer to the middle of the cassette without going as far as the deepest rings. mGYDY also names fat snow bikes as a use, so the ring covers a wide spread of frames; the tape measure decides where yours lands.

Each maker measures offset from its own reference, so compare by measuring the fitted ring, not by trusting a number across brands. Measure from the frame centre to the teeth and match it to the middle cog within a few millimetres.

Speed in any gear is cadence times ratio times wheel circumference. At 90 rpm on an 11T cog, the four sizes give these top-gear speeds.

The small end is about heat as much as gearing. A BBSHD climbing on a big ring turns slowly under high current, and that heats windings and controller quickly. Each step down in ring size keeps the motor spinning faster up the same grade.

• 32T: steep trails, cargo, towing, heavy riders on 48V.
• 34T: hilly singletrack with some road between trailheads.
• 36T: hilly commuting; the most balanced choice for mixed use.
• 38T: commuters who climb often but still want road pace.

All four sizes also go easier on the nylon primary gear inside the drive, which sees its worst loads at low speed and high torque. That failure mode is traced in the nylon gear guide.

mGYDY machines the ring from 6061/7075 aluminium and gives it T6 heat treatment, the standard process that brings both alloys to their high-strength state. 7075 is the harder of the two grades and resists tooth wear better; 6061 is tougher and easier to machine. The ring is sandblasted and anodised, a surface treatment that adds corrosion resistance and a hard skin.

CNC-cut teeth are meant to mesh smoothly with the chain, which cuts noise and wear. The ring is rated for 7- to 12-speed chains, a wide range that covers old 7-speed freewheels through current 12-speed cassettes.

• 7–9 speed: wider chains, common on budget conversions and hub gears.
• 10–11 speed: most mid-range 1x trail drivetrains.
• 12 speed: modern wide-range cassettes; check the chain sits squarely on the teeth.

Even hard-anodised 7075 is a wear part on a mid-drive. Chains stretch, and a stretched chain rides up the teeth until they hook.

1. Check chain wear with a gauge at regular intervals.
2. Replace the chain before it passes the wear limit.
3. Inspect the teeth for a shark-fin profile when you swap chains.
4. Replace ring and chain together if a new chain skips under power.

A gear sensor that briefly cuts motor power during shifts also protects the teeth, since shifting under full load is one of the harshest moments a ring sees.

The ring is described with a standard 104BCD mounting design. Work out how the ring will attach on your motor: with the stock ring off, count and measure the fixing points and compare them with the ring's holes. If your drive has a 104BCD spider fitted, the pattern will match directly. BBS01 and BBS02 motors use a different spline and are not listed.

If the holes line up only with force, stop there. Filing or drilling a chainring changes how the load passes through it, and a cracked ring under 1000W is a crash waiting to happen. A ring that seats flat, with every bolt threading in by hand, is the sign of a correct fit.

Installation takes the standard tools:

1. Remove the drive-side crank arm with a matching crank puller.
2. Take off the stock ring or adapter.
3. Fit the mGYDY ring with medium-strength threadlocker on each bolt, tightened in a star pattern with a torque wrench.
4. Refit the crank, shorten the chain and check chainline in every cog.

Moving from a 46T stock ring to 36T removes roughly two to three inner-plus-outer link pairs. Crank and chain steps run in order in the BBSHD install guide.

• Fat bike with a wide rear end: the ebsenopower 8 mm offset ring.
• Need a 104BCD face first: the Cicony 104BCD adapter.
• Want 40T–42T instead: see the BBSHD chainring guide.