Chain and Chainring Requirements for Internal Gear Hubs

Rohloff · 3X3 · Revolute

The Short Answer

A 1/2“ x 3/32“, 8-speed (or “narrow” internal gear hub/e-bike) chain, paired with a 3/32“ single-speed chainring.

This is the baseline for all three systems, and for good reason: based on verbal confirmation, the manufacturer of 3X3 (H+B Hightech) requires the exact same specifications as Rohloff for compatibility and retrofit reasons. In short, if you know the Rohloff formula, you know the 3X3 formula as well.

The 1/8“ “thick” single-speed chain is a legacy of classic coaster-brake and old Sturmey-Archer setups. It is not suitable for modern, high-torque internal gear hubs.

Why?

The pitch on all bicycle chains is 1/2“ (12.7 mm); only the width varies, specifically in two dimensions:

Internal clearance (where the tooth sits): 1/8“=3.30 mm · 3/32“=2.38 mm · 11/128“=2.18 mm (9–12 speed)
External width (across pins): 6/7/8-speed 7.1–7.3 mm · 9-speed 6.5–6.8 mm · 10-speed 5.85–6.2 mm · 11-speed 5.5–5.7 mm · 12-speed ≈5.25 mm · 1/8“ single-speed 8.5–9.5 mm

Internal gear hubs do not have derailleur plates to squeeze between, so the external width is irrelevant. What matters is the internal clearance and the matching tooth thickness on the chainring and sprocket. This allows for a beefier, more durable chain under an internal gear hub than on a derailleur system.

Narrow-Wide: This feature is on the chainring, not the chain. Because the inner and outer links of a chain have different clearances, the NW chainring utilizes this by using alternating thick and thin teeth. It cannot be used with a front derailleur. While useful under an internal gear hub, proper chain tension (eccentric bottom bracket, sliding dropouts, or chain tensioner) and chainline are far more important.

Rohloff SPEEDHUB 500/14

Chain: Any 1/2“ x 3/32“ 8- and 9-speed chain works, but an 8-speed is recommended due to its thicker side plates. A 1/8“ chain will fit the sprocket (max 8.5 mm), but it is no stronger, not recommended, and will not fit through the chain tensioner.
Minimum gear ratio: Chainring-to-sprocket ratio ≥1.9 (for riders over 100 kg or tandems: ≥2.5). Valid 1.9 pairs include: 40:21 · 36:19 · 34:18 · 32:17 · 30:16 · 28:15.
Chainline: 54 mm; 57 mm with a splined sprocket.
Chain tensioner: Works exclusively with 1/2“ x 3/32“ and 1/2“ x 11/128“ chains. Tension capacity is 10 links; mounts to the derailleur hanger; lateral adjustment is done via spacers. Standard: Art. 8250 · DH Shorty: Art. 8245 (max 17T sprocket). There is no chainring size limit—both 30T and 32T work flawlessly with it. On full-suspension frames, the chain must be sized at full compression so rear wheel travel is not restricted.
Recommended chains: KMC X8 EPT / Shimano CN-HG40–HG71 / Connex 808 (non-e-bike) · KMC e1 EPT narrow or Z1eHX Narrow EPT (e-bike).

3X3 NINE / SIX (H+B Hightech)

Chain: Same as Rohloff—1/2“ x 3/32“, or an e-bike-rated version for e-bikes. The manufacturer confirmed that their requirements align with Rohloff for compatibility and retrofitting.
Factory documentation notes:
- NINE: 554% gear range, 250 Nm allowable input torque. SIX: 292% gear range and 160 Nm allowable torque. Both are grease-lubricated (no oil changes), shiftable at a standstill, and allow jumping multiple gears.
- Wear parts according to manufacturer: Sprocket, chain, chainring, belt, pulley, tensioner pulleys, cables, grip rubber, and brake rotors.
- A chain tensioner is required if the chain cannot be tensioned properly otherwise; without it, the chain may drop off the sprocket.
- Belt drive compatible if the frame supports it (Gates).
- The gear ratio is tuned via primary tooth counts; on e-bikes, manufacturer regulations regarding component replacement must be followed.
Allowable primary ratio calculation (to avoid exceeding 250 Nm at the rear wheel):

iprimary=250(rider mass [kg]×9.81)×(1000crank length [mm])+motor torque [Nm]
Max system weight: 250 kg. Not compatible with coaster brakes. Designed exclusively for rear wheel installation (intermediate drives require special approval).

Revolute HUB1 / HUB A8

Chain: Also 1/2“ x 3/32“. The HUB1 sprocket uses a standard 9-spline pattern known from HG cassette bodies (a standard derailleur sprocket)—hence it requires an 8-speed or e-bike “narrow” chain.
HUB1: 250 Nm input torque, ≈2 kg, oil-lubricated with a 5,000 km oil-change interval, standard 6-bolt disc mount, available in quick-release and thru-axle setups.
- The hub does not freewheel in reverse; therefore, a freewheel at the crankset is required to pedal backward—both on e-bikes and non-e-bikes.
HUB A8: Fully automatic sensor-based shifting, wireless and self-powered (no external power needed). Target cadence is adjustable via an app, with an optional wireless trigger.

Chainring Selection (For All Three Systems)

Use a 3/32“ single-speed chainring, preferably heavy-duty/steel for e-bike setups. A Narrow-Wide tooth profile is acceptable, but not mandatory.

30T or 32T? (Rohloff Example, Logic Applies to All)

Chainring	Sprocket	Ratio	Assessment
30T	15T	2.00	Well within limits
30T	16T	1.875	On the edge of factory spec
30T	17T	1.76	Not allowed
32T	16T	2.00	Well within limits
32T	17T	1.88	On the edge of factory spec
32T	18T	1.78	Not allowed

Given the choice, 32T is the safer option: you stay within limits even with a sprocket one size larger, and a higher tooth count wears down more slowly.

Bosch Gen 4 – Do You Need to Replace the Spider?

Two mounting types exist on BDU4XX motors (Performance Line, Performance Line CX, Cargo Line, Speed):

Direct Mount: One-piece chainring with lockring + O-ring; requires a Bosch spider tool.
Spider + 104 mm BCD Chainring: The chainring mounts to the spider via 4 bolts.

Regular vs. Boost: The spider comes in two chainline variants, differing by several millimeters. A Boost rear end on an e-MTB requires a Boost spider.

If in doubt about your existing spider:

Distance between center points of two adjacent holes: 73.5–74 mm → 104 mm BCD ( standard fit for any 104 mm single-speed chainring).
What varies by manufacturer: Which side (inner or outer surface) the chainring seats on and at what offset—this shifts the chainline, not the BCD. Buying a spider with known geometry is easier than reverse-engineering an OEM spider.
On e-bikes, altering the chainring tooth count changes the overall gear ratio; make sure to adhere to manufacturer guidelines for component replacement.

Measuring with a Caliper

Internal Clearance: 3.30 mm=1/8“ · 2.38 mm=3/32“ · 2.18 mm=9–12 speed.
External Width: See numbers listed above.
Wear: Measure with a chain wear tool. Replace at 0.75% for standard internal gear hub setups, or closer to **0.5%**on e-bikes.

Order List (Bike-Discount)

#	Item	Link
1	Chain – KMC Z1eHX EPT Narrow, 1/2 x 3/32“, with MissingLink	Bike-Discount Product Link
2	Spider – Miche E-Bike Spider Bosch MTB Boost Gen. 4, BCD 104 mm (with lockring)	Bike-Discount Product Link
3	Chainring 30T – Race Face Narrow Wide 104 mm, 30T	Bike-Discount Product Link
4	Chainring 32T – Same product, 32T version	Bike-Discount Product Link

Additions: Regular spider (for non-Boost frames) – Bike-Discount Link · Bosch system chainrings, lockrings, sprockets – Bike-Discount Category Link