Description
Confused about what all the shorthand means on our rim codes?
Here’s how to interpret them:
RIM REFERENCES
D/W or S/W
This means ‘double wall’ or ‘single wall’ and you will see this commonly on a wheel or rim that is compatible with rim brakes. This refers to the internal profile of the rim, where single wall is considered weaker than a double wall rim. A double wall creates additional stiffness and strength in the rim against things like brake force. A double wall rim also has increased strength against the pressure from the tyre bead pushing out from the inside of the rim. You will find a double wall rim is generally of higher quality than a single wall.
Eyeletted or Non Eyeletted
This is referring to where the nipples of the spokes are in the rim of the wheel. There are often eyelets (usually silver) that surround the spoke hole in the rim. You will generally find an eyeletted rim is stronger as these eyelets reinforce the area of high fatigue from the spoke nipples.
MSW or Non MSW
This refers to a machined side wall or a non machined sidewall. This is used to describe a wheel rim that is compatible with rim brakes, and refers to the braking surface area. You will be able to see a machined sidewall on a rim, it is the flat portion where the brake gains purchase on the rim. A machined sidewall provides a better gripping surface for your brakes, giving you increased braking power.
A/V, S/V or F/V
These acronyms refer to the type of valve hole machined into the rim. An A/V is an ‘auto valve’ so this is what you would find on a car tyre. This type of valve is more commonly known as a Schrader Valve type. An F/V is a French valve or a Presta type valve. This is a longer thinner type of valve that you would find on road bikes or gravel bike wheels.
P/J or S/J
These refers to Pin Joint & Sleeve Joint respectively, and they are describing the method of connecting the two ends of the rim profile. Pin Joint rims have small pins within the profile of the rim which ensure a stiff connection between the ends. Depending on how ‘tough’ the rim has been designed, there may be 2 or 4 pins within the profile.
Sleeve Joint rims on the other hand have an overlapping connection within the rim profile which provides added stiffness. This strength is a result of the greater surface area of each side of the profile touching.
28H, 32H, 36H etc
These numbers followed by an H refer to the spoke ‘Hole’ count of the rim. This means that a 36H rim requires a corresponding 36 spokes, and a hub whose spoke spoke count is also 36. You will often find rear wheels with a higher spoke count than the front wheel, and more aerodynamic wheels will have less spokes. A higher spoke count is often preferred for a stronger wheel such as in an ebike, a cargo bike or a downhill bike. And 32H is probably the most common type in modern wheels.
ERD
ERD refers to ‘Effective Rim Diameter’ and this is a measurement used in wheel building as it is required for spoke calculations. The ERD is the closest point to the hub, so a deeper rim would have a different ERD to a shallower one. You only need to know the ERD if you are calculating spoke lengths to build the wheel. It can be measured manually if you don’t have this information about your rim.
ISO / Bead Seat Diameter
This one is trickier to explain, in that it is a measurement listed on rims that is not often prefaced with ISO or BSD. It usually just appears as a series of numbers where the first number is 2 digits, followed by a 3 digit number, or the reverse. For example 622 x 13 or 571 x 14.
The ISO is the International Standards Organization, and the 3 digit number refers to the Bead Seat Diameter. The bead seat diameter is a number that’s important for choosing a tyre for the rim. The bead of the tyre must sit inside the lip of the rim and ‘seat’ in the rim in order to stay on the rim when inflated. The two digit number in the listing of 622 x 13 refers to the internal width of the rim. You would need to know the width of the rim when choosing a tyre, as a tyre that is very wide could blow off a rim that is not wide enough.
