Crank geometry & Q-factor
MIRANDA / CRANK GEOMETRY
The correct motor interface is the starting point. The right crank pair also needs the correct shape on each side of your bike.
Start with the complete reference on both existing cranks. Keep the length, interface and full geometry codes together, including any letters or prefixes.
Why the two sides can be different.
Left and right mean the sides of the bike when you are riding it. The right side is the chainring side. Some bikes use a motor or spindle mounted off the frame centreline. The crank pair may need different profiles to put the pedals in their intended positions.
01 / THE PRINCIPLE
Centred mounting, matching profiles
Equal crank outreach can suit a centred assembly. The exact profile still depends on the motor, spindle and frame; a centred motor does not automatically mean Q:16.
02 / THE PRINCIPLE
Shifted mounting, same profiles
A motor or spindle mounted to one side can move the pedal positions off centre when equal crank profiles are used. A wide enough pair can still be in the wrong lateral position.
03 / THE PRINCIPLE
Shifted mounting, different profiles
Different left and right crank outreach can restore the intended pedal positions. Match the specified pair for your bike, including the correct profile on each side.
Schematic views from behind the bike, not to scale. Red dashed line: frame centre. The drawings explain a principle; they do not prescribe a Q-code for a particular bike. Judge the mounting geometry, rather than the outside shape of the motor cover.
A Q-code is not the bike's total Q-factor.
Q:16 is a Miranda crank-geometry designation. It does not mean that the assembled bike has a 16 mm Q-factor. Total Q-factor is the lateral distance between the outer crank faces where the pedals seat. DBC is the distance between the inner crank faces shown in the assembly drawing.
Neither the total width nor DBC alone tells you whether each crank is in the correct position relative to the frame. Check the complete left/right setup and frame clearance.
Keep the complete code.
Q:16, 55Q:16 and Q:16-UC are different Delta catalogue geometries even though all contain “16”. FB and other prefixes or suffixes are part of the reference too.
| Full profile | Dimension A | Dimension D |
|---|---|---|
| Q:16 | 16.1 mm | 30.2 mm |
| 55Q:16 | 16.1 mm | 35.7 mm |
| Q:16-UC | 16.1 mm | 42.0 mm |
A and D are dimensions in the original Delta drawing, not a home-measurement recipe. These examples do not transfer automatically to other crank models.
Choose your pair in three steps.
- Read both cranks.Photograph the inner face of the left and right crank, including all markings, length and any part codes. Keep each photo labelled left or right. The Miranda FAQ identifies the right crank by an R engraved on its inside.
- Match the whole reference.Confirm the motor or spindle interface, crank model, length and full geometry code for both sides. A mixed label such as Q:8/Q:16 is a pair specification, not a range. Do not treat Q:8/Q:16 and Q:16/Q:8 as interchangeable, or assume the slash order identifies the sides unless the product reference says so. Numbers on another brand's cranks do not automatically translate to Miranda Q-codes.
- Confirm the new assembly.For an unchanged bike with a correct existing pair, the exact replacement reference is the strongest starting point. If the length, crank shape, motor or frame has changed, check the intended pedal positions and crank-to-frame clearance on both sides throughout a full rotation, using the bicycle and component manufacturers' specifications.
No readable code? Here is the next step.
Send Miranda the details below. Clear photos are useful for identifying the parts; a side-on bike photo alone cannot establish an exact Q-profile.
- Bike brand, model and year, if known.
- Motor model and complete drive-unit reference.
- Left crank: brand, length and every readable marking.
- Right crank: brand, length and every readable marking.
- Photos of both inner crank faces, the motor label and each crank next to the frame.
- What has changed from the original setup.
What should a mechanic measure if the references are missing?
A mechanic can establish the frame centre plane and record the lateral position of each pedal-seating face separately. The frame centre must be established correctly; the motor-cover edge is not a datum.
Record left and right positions, total Q-factor, DBC and the closest crank-to-frame clearance through a full rotation. Equal-looking gaps to the chainstays are not a reliable substitute: the frame itself can be asymmetric.
These measurements support a comparison with the exact crank and motor drawings. They do not, by themselves, produce a universal “choose Q:16” rule. Fit the specified fixing hardware and follow the installation instructions for the exact assembly.
Technical references
- Miranda 2026 catalogue: Delta geometry, PDF page 15 ↗
- Miranda 2026 catalogue: motor tables and Q-factor / DBC, PDF pages 29-30 ↗
- Miranda: Delta technical geometry ↗
- Miranda store: crank identification and fitting FAQs ↗
Reviewed 1 November 2026. This guide helps identify the correct geometry; the exact bike, crank and motor references determine the final assembly.
Miranda & Irmão, also known as Miranda Bike Parts, is a company with over 75 years of existence, producing cranksets, brakes, levers, grips and reflectors, currently being the european manufacturer of premium bicycle drivetrain components, for ebikes, MTB, EMTB, road, trekking, commuting, and city bikes.
First established as an individual business in 1940, it became a family-owned company by 1950, manufacturing headlamps, rear lamps, and air pumps.
By the 1960's, Miranda was on its path to success, having increased its industrial area thus widely developing its manufacturing capabilities, and expanding to a new range of products such as motorcycle hydraulic brakes, speedometers. grips, switches, and klaxons.
The introduction of plastic injection technology, in 1978, brought a new surge of development to this already striving company. Later on, the 90's Miranda installed the equipment and technology of cold-forged aluminum.
Nowadays, Miranda has extended production to a new range of bicycle brakes and cranksets, and has been progressively going into the medium and high-end market of bicycle components.
Miranda is now supplying most of the European top brand bicycles and exporting to a wide range of countries, enlarging every year a strong reputation of the quality maker and a reliable industrial partner.
