Technical glossary

Marking in millimetres

Often used for road or city tires.

A marking in millimetres can be expressed as follows on a tire:

Example: 650x32A (32-590)

What does that mean?

The first number (650) denotes the overall diameter of the tire in millimetres.

The second number (32) denotes the tire section in millimetres.

The letter A indicates a 590 mm rim.

The numbers in brackets (32-590) correspond to the ETRTO marking, which is explained above.

Marking in inches

Mainly used for MTB, City and Gravel bikes.

A marking in inches can be expressed as follows on a tire:

Example: 26*1 3/8 1 1/4 (32590)

What does that mean?

The first number (26) indicates the overall diameter of the tire in inches.

The second number (1 3/8) denotes the tire height in inches and fractions of inches.

The third number (1 1/4) gives the tire section in inches and fractions of inches.

The numbers in brackets (32*590) correspond to the ETRTO marking, which is explained above.

Special case of marking in inches:

Example : 29x2,40

What does that mean?

The first number (29) denotes the tire's overall diameter in inches.

The second number (2,40) is the overall cross-section.

Below, in alphabetical order, you will find simple definitions of technical cycling terms.

B >

Bar: this is a unit of pressure generally used for tires. In English-speaking countries, PSI is the unit most often used. Michelin provides you with tire pressure tables for your bike in Bars and PSI.

C >

CO2 cartridge: very useful in case of emergency, this small cartridge, about the size of a thumb, is most often used as a substitute for a pump to inflate your bicycle tires. It usually requires a specific adaptor to plug onto the valve and release the air.

Compressor: a compressor (or air compressor) is an inflation device often available from petrol stations. Mainly intended for cars, it can also be used to adjust the pressure of a bicycle if its tires are Schrader valve-equipped and the compressor has specific settings for cyclists.

E >

E-25 / E-50 bikes: E-25 bicycles are electric engine assisted bicycle, with assistance until 25km/h. E-50 bicycles are are electric engine assisted bicycle, with assistance until 50km/h.

ETRTO : European tire and Rim Technical Organization. This is the organisation responsible for defining tire standards at European level.

F >

Flexible bead (FB) - or Foldable Bead: Invented and perfected by Michelin, they are made of aramide (e.g. Kevlar®). They are lighter and allow the tire to be folded.

G >

Gum Wall (GW) sidewall is coated with a layer of rubber to give it stiffness and protect it. Advantage : resistance to sidewall tears.

Gum-x: MICHELIN GUM-X Compound is designed to optimize grip and rolling speed. It’s adapted to each category in which you will find it in MICHELIN ranges.

M >

Magi-X: MICHELIN MAGI-X Compound is designed to give maximum grip with no compromise. This compound is adapted to each category in which you will find it in Michelin ranges.

MTB: This is simply an abbreviation commonly used to designate Mountain Bikes.

O >

Overlap: Central part of the casing.

P >

Presta valve: it is smaller than a Schrader valve and requires unscrewing the shell to inflate. See our article on tire valves.

Protek Max: This is Michelin's puncture-proof inner tube. The combination of liquid sealant, specific square shape and butyl technology ensures excellent pressure hold. More information about MICHELIN Protek Max.

PSI (Pounds per Square Inch): A unit of pressure generally used in English-speaking countries, particularly for tires. Bar is the other pressure measurement unit most often used in other countries. Michelin provides you with tire pressure tables for your bike in PSI and Bars.

R >

Rolling resistance: it is the friction generated by tire contact with the ground. Along with air resistance, and gravity if you're going uphill, it's one of the main factors that makes cycling more difficult. Read our article about Rolling Resistance.

S >

Sealant: tire sealant is a self-sealing liquid that is injected in tubeless-ready bicycle tires or in tubular inner tubes. It can plug punctures without stopping to ride. Read our article "How to use bike tire sealant".

Section: Width of the inflated tire from sidewall to sidewall.

Shore is a unit of measurement ranging from 0 to 100. This unit measures the hardness of elastic products. (From 0 soft to 100 hard).

Shrader valve (standard): the Shrader has become a standard. It's the same size as a car tire valve, so you can adjust the pressure at a service station if you don't have an air pump. See our article on tire valves.

Skin Wall (SW) sidewall allows us to make out the texture of the casing through its transparency. Advantages : lightweight, flexible and efficient.

Suspension travel: the ability of the front and/or rear wheel to move vertically to absorb shocks and overcome obstacles.

T >

TPI (Threads Per Inch): The number of casing threads per inch, affecting weight, flexibility, and performance.

Tread: The tread is the part of the tire, mostly constituted of rubber, which can come in contact with the ground.

Tubeless: tire fitted without inner tube. It needs specific rims. The advantage of the tubeless tire lies in its ease of implementation. As the rim is already fitted with a valve, the tire just needs to be fitted and maintained.

Tubeless Ready (TLR): Tubeless Ready tires can be fitted without an inner tube provided that a tubeless wheel is used, the maximum pressure is not exceeded, sealant is added and the tire pressure is checked before each ride.

Tubetype: this is simply the type of tire that contains a removable inner tube.

Tubular: a tubular tire is a type of bicycle tire that is sewn around the inner tube to form a torus. The whole thing is then glued to a tubular rim.

tire sizes: on your sidewall, your bike tire size will probably be given in one of these three ways: ETRTO measurements (for example: 23-622), Imperial measurements (for example: 29 x 2.10) or Metric measurements (for example: 700 x 23C). For more information, see our article "Bike tire Sizes explained".

U >

UCI: the International Cycling Union is an organization whose aim is to develop and promote cycling in cooperation with the national federations.

UST (Universal System Tubeless): A tubeless standard where the rim and tire are designed as a single system.

W >

Weight: The weights stated are given as a guide with a tolerance of plus or minus 7 %.

This variation is due to the natural elements inherent in the construction of tires.

Wire bead (WB): Being made of steel wire, they are cheap.