Motorcycle Acronyms | WTF do they mean?

Have you ever been left baffled by some clever-dick salesman reeling off a bunch of letters? Or flummoxed by a web post or magazine article because everything’s DRL this and TFT that? Well you won’t be the only one. So to help shed some light on the confusing motorcycle acronyms that are slowly taking over the industry, here’s a glossary of all the ones we can think of. If there are any we’ve missed, let us know…

DOHC/SOHC

Double Overhead Cam/Single Overhead Cam.

In simple terms, cams are the things in your engine that open and close your inlet and exhaust valves. Most modern bike engines have a camshaft to operate the inlet valves and a separate one to operate the exhaust valves; so ‘double’ overhead cam (sometimes called ‘dual’).

Some engines still do have a single overhead cam. That just means the exhaust cam lobe and the inlet cam lobe are all on the same shaft.

It’s ‘overhead’ because the cams are directly driving the cams from above, rather than having a complicated system of pushrods and levers.

TDC

Top Dead Centre

This one isn’t really that important for the normal everyday motorcyclist. TDC refers to the point when the piston is at the very top of it’s stroke. It’s important when you’re building engines, tuning engines, checking your valve timing or anything like that.

RPM

Revs Per Minute

The amount of times your engine rotates in one minute. In other words, the unit of measurement used to describe engine speed.

BHP/HP/PS

Brake Horsepower/Horsepower/Pferdestärke

Annoyingly, manufacturers tend to talk about power figures in whichever one of these they feel like. And although they’re similar, they’re not the same.

‘Power’ is always the same; it’s the measurement of work divided by time (with work being force multiplied by distance). But we all already knew that.

Brake horsepower is the measure of power when measured using a dynamometer (often at the back wheel), so includes all the frictional losses associated with gearboxes and final drives.

Horsepower technically refers to the theoretical amount of power an engine can make, and is calculated, rather than measured, so it’s not really relevant. A lot of manufacturers will talk about HP figures though, which have usually been measured at the crank.

Pferdestärke is the German word for horsepower. Pferde is horse. Stärke is power. PS is actually a metric measurement of power (HP is imperial), so 1PS is slightly different to 1HP. In fact, 1PS is about 1.01HP.

Nm/ft-lbs

Newton-meters/Foot-pounds

Again, annoyingly, some manufacturers use the metric (Nm) and some use the imperial (ft-lbs) units for engine torque. Torque, being a turning force.

1Nm is the amount of turning force you’d have at a fulcrum (pivot) if you applied 1 newton of force on a 1 meter lever.

1 foot-pound is the amount of turning force you’d have if you applied one pound of force with a foot-long lever.

1Nm equals about 0.74ft-lbs

CC

Cubic Centimetres

This is an engines capacity, or swept-volume, in cubic centimetres, or CC³ . It’s the area of the cylinder bore, multiplied by the length of the piston stroke, multiplied by the number of cylinders. More CC means a ‘bigger’ engine and the potential for more power.

IMU

Inertial Measurement Unit

These little babies are responsible for measuring the attitude of your bike, at any given time. Most modern, reasonably high spec bikes will have a 6-axis IMU, capable of measuring up-down, backwards-forward, right-left acceleration, as well as roll, yaw and pitch.

It’ll feed all this info into the bikes ECU which’ll then decide how much throttle, braking etc. it wants to let you have.

ECU

Engine Control Unit/Electronic Control Unit

These have been around for a long time, but nowadays they are more and more advanced with some bikes having several ECUs. The ECU is a computer that controls everything from the ignition timing to the traction control, and all the other electronic rider aids.

TC/TCS/DTC

Traction Control/Traction Control System/Dynamic Traction Control

Traction control is an electronic rider aid that limits the amount of power you can have, if the bikes computer thinks the back wheel is spinning, or is about to spin.

The problem is, it’s often called different things. For example DTC could mean Dynamic Traction Control (BMW terminology), but it could also mean Ducati Traction Control. Just remember, if it’s an acronym with TC in it somewhere, it’s probably referring to Traction Control.

ABS

Antilocking Brake System

Since 2013, ABS has been mandatory on all bikes over 125cc in the UK. If your brakes lock up, the ABS system releases them for you. The idea is, it’ll stop you crashing. The reality is, it quite often causes crashes.

TFT

Thin Film Transistor

This is a type of LCD (Liquid Chrystal Display) that a lot of modern bikes use as a dashboard. They are very trick, very bright, and allow you to see a ton of info on the dash.

DRL

Daytime Running Lights

For some reason, all the manufacturers bang on about these, as though they are a massive selling point. In reality, they’re just sidelights that you can’t turn off. Big wow.

LED

Light-Emitting Diode.

An LED is a bit like an old fashioned filament light bulb, but better in every single way. They last longer, run cooler, use less energy and are brighter. Lots of modern bikes use them for headlights, tail lights and everything in between.

DCT

Dual Clutch Transmission

This is a technology that a lot of Honda adventure or touring models come with the option of. To put it simply, it’s a semi-automatic gearbox.

TPMS

Tyre Pressure Monitoring System

This is a system that measures the air pressure in your tyres, believe it or not. It’s starting to appear on ore and more bikes, and will let you know, usually by a warning icon on the dash, if your tyre pressures are outside a pre-set window.

PSI

Pounds per square inch

PSI is a unit of measurement for pressure. In motorcycling it’s often used when talking about tyre pressures but really can be used to measure anything which has a pressure; like checking a fuel pump or pressure testing an engine.

EFI

Electronic Fuel Injection

Most modern bikes are ‘fuel injected’, rather than carburetted. This means the bikes fuelling is controlled using a fuel pump and some computer algorithms, rather than carburettor and a simple throttle cable.

RBW

Ride By Wire

Usually in relation to the throttle, this is where actuation of a particular control is achieved electronically (using a wire), rather than a mechanical cable.

OBD/OBD-II

Onboard Diagnostics/Onboard Diagnostics 2

Sometimes called ‘Onboard Data’, OBD is an electronic system that allows access to a bike’s (or a car’s) computer, usually to diagnose any faults. OBD-II is just the latest version of it.

There will be an OBD-II port somewhere on the bike (if it’s compatible), which if you have the correct equipment, you can connect to and see the status of all the electronic components. It’s also possible to tune various parameters within certain components, again, provided you have the correct equipment.

USD (forks)

Upside-Down (forks)

Upside-down forks are actually more common than ‘traditional’ forks these days. If you look at any modern sportsbike, it will have USD forks. It is where the inner stanchion tube is at the lower end (attached to the front wheel spindle) and the outer tube is at the top (attached to the top and bottom yolk.

Traditional forks worked the other way round.

USD forks tend to be better because you have less ‘un-sprung’ weight; that’s weight that you can’t control with the suspension.

RSU

Rear Suspension Unit

This isn’t specific to any type of rear suspension unit, but tends to mean a spring and strut type shock absorber.

DOT

Department of Transport

If you see this, it just means that a certain product has been approved by the Department of Transport. It will quite often be followed by a number which’ll relate to the particular standards it has passed. For example DOT 4 brake fluid will be a step up from DOT 3. DOT 3 brake fluid will boil easier.

OE/OEM

Original Equipment/Original Equipment Manufacturer

Original equipment is all the parts you get on a standard, showroom spec bike. And an original equipment manufacturer is the company that makes them. The OEM isn’t necessarily the bike manufacturer (Kawasaki, Honda, Ducati, etc), the OEM can be a company that makes a specific part for a standard bike; Brembo, for example, who make the stock brakes for plenty of road bikes.

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