Grease is an often talked about but little understood. It can have a significant impact on performance on a bike specifically in the area of transmission frictional losses (watts). This guide covers the practical aspects of using grease as a lubricant and as an assembly aid.
Following a number of questions arising from a video where the bearings on a set of Winspace wheels were changed, the guide below gives you a brief synopsis of grease for bicycle applications.
The technical info has been dampened to appeal to a wider audience.
Typically, grease is used for either lubricating moving parts or as an assembly aid. The types of grease for these two applications are quite different.
Grease in moving parts such as bearings is considered the second biggest contributor to drag after the bearing seals. Grease is usually petroleum based with additives and thickeners. A universal scale for measuring grease is called the NLGI number, alternative standards do exist but this is the most widespread. It is shown below
|NLGI number||ASTM worked (60 strokes)|
penetration at 25 °C
tenths of a millimeter
|Appearance||Consistency food analogy|
|0||355-385||very soft||brown mustard|
|2||265-295||“normal” grease||peanut butter|
|4||175-205||very firm||frozen yogurt|
|6||85-115||very hard||cheddar cheese|
The scale is straightforward. As the number increases, the grease becomes more viscous. Thicker greases are used at higher temperatures.
Lubricating Grease (Bearings)
For bicycle dynamic applications, those who want to save the absolute maximum would use a light oil and remove the bearing seals to minimize friction. This has diminishing returns as the maintenance intervals would be frequent and the costs are prohibitive. On long rides, the bearing may be in a state with no lubrication once the oil has “leaked” out. A slightly better option is to use a non-contact sealed bearing and either a 000 or 00 grease. This provides very low friction and will easily have sufficient containment to last 10-20hours (this range increases with 00 and thicker greases). This is common amongst triathletes. 000 grease can be extremely expensive.
It is very important to prevent overfilling of bearings. Only 33% of the unoccupied volume is required to be filled, it does not and should not be packed fully. Doing so will cause the bearing to overheat and lead to premature failure. It also increases friction exponentially. As the bearing rolls, the grease heats up and it turns into a semi oily mixture, over time this will leak out of the seals so they will need repacking. It should be noted that the bearing friction will reduce once they are warm. Competitors in events such as time trials would benefit from “warming” their bike up beforehand.
Assembly Grease (Anti Seize)
For assembling components, the requirements of the grease are very different, they are in a “use once” and then forget application to aid assembly and disassembly. In this instance, the aim is to minimize installation/removal friction and a slightly thicker grease is preferred. An NLGI 2 or higher would be ideal. It is thick enough to adhere to surfaces to minimize friction and viscous enough to prevent dripping off. It is important to minimize the amount of grease used for assembly. It is possible to Hydrolock components and thus shift their desired position by using too much grease. Copious grease attracts dirt and grit which emulsifies into an unwanted grinding paste leading to wear of adjacent parts.
Grease as a Water repellant
Using grease as a water repellant is common especially in sealed areas such as bottom brackets and wheels. A minimum of Grade 2 or higher will be required for this application as it must have sufficient viscosity to prevent wash off. Grade 3 is recommended as it has better resistance to dirt and grit emulsification.
Grease Composition (Lithium, Teflon, Copper etc)
The NLGI rating will effectively control the materials that are used. For example, copper grease is rarely found in low NLGI numbers because it contains copper as an abrasive and is unsuitable for moving parts, this is often why it is called anti-seize compound. In contrast, lithium and teflon are found at the more dynamic end of the scale owing to reduced friction.
Carbon Grease / Fiber Paste
Carbon grip paste is often described as a grease. The solvent medium is a grease with abrasive particles embedded within the material. It is designed to increase friction by providing “bite” between surfaces. It does not function like grease in the typical sense and is not covered in this guide.
For most, it is not practical to have multiple different grease types sitting on the shelf. For this kind of user, an NLGI 0, 1 or 2 would be recommended.
For someone who is keen to go fast, an NLGI 00 or 000 grease would be recommended for bearing lubrication.
For assembly applications NGLI 2 or higher is recommended.
- Shell Gadus (formerly called albida)
- Mobil SHC (007 is a very popular choice as a go to all grease)
- Total Multis
- Castrol Spheerol
All of the above greases are available in different viscosity grades.