Grease use in the bicycle production

• Hi, welcome back to 128.bike, channel with a lot of useful information for the bicycle industry

• Lately when talking with bicycle production managers and product developers I have noticed that there is a lot of confusion about the use of grease in the assembly process. Grease being a very important part of the protection from rust and weather, as a friction control component should be understood perfectly and used only when it is necessary.

• With the constant change in the workers working on the assembly line production managers are struggling these days to properly train people on the correct assembly process. Many times even the production managers themselves are promoted to that position from another sector and trying to learn how to handle production in a really short time period. Purchasing managers seem to have similar problems as well. All of this can be very frustrating for all players in the production process.

• This is why I want to share as much as possible on one platform to help people in bike and e-bike production to make a claim free products as much as possible.

• In this video I will focus on the bottom bracket and chainwheel assembly because this point in the production process is the most sensitive one when we are talking about the use of grease and tightening torque importance.

• First place which is very important is the use of grease on the thread of the bottom bracket cups and BB housing on the frame.

• When using a steel or alloy cups on steel or aluminium frames then it is recommended to use grease.  This is intended to make the assembly easier and to prevent the cups getting stuck in the frame making service almost impossible. With steel frame and cups rust causes the problem. But some of the toughest service I had was with aluminium frames and steel cups. When steel cups get stuck in aluminum frames it is near impossible to get them out.

• Important thing is to apply the grease to the frame and then screw in the cups. Never apply the grease on the cups and then screw them in the frame. This causes the grease to be pushed outside of the frame and then there is no friction in the thread and the shoulder of the cup and the frame. In return this causes the cup to untighten during the use.  So very important to remember this!

• Important note in serial production: always use grease application with a tool or a stiff brush with a long handle. This will help the assembler avoid getting the hands greasy. If his hands are greasy when handling the frames, especially matt painted ones, he will do irreparable damage to the paint job and leave finger marks all over the frame which are very difficult to clean, even impossible. This will look really bad to the customer under the shop lights.
• Another issue is that type and quantity of grease to be applied to the thread is never specified by any producer. This results in unstable results in tightening forces and friction of each assembly on bikes. If using steel cups in production you should do extensive testing and try to use similar amounts each time.
• Most commonly used is lithium grease as it is most versatile and multipurpose grease.  And what I saw most commonly used is a painting brush with a long handle used to apply the grease to the frame threads.
• Now in case of using composite cups things are much more simple and there is a better stability of process here. It is recommended that no grease is used in the assembly process because there is no chance of composite material getting stuck in the frame no matter if it is alloy or steel. So there is one process less in the assembly, meaning it is faster. The results you get will always be same. Composite material and thread will adapt to the frame thread and provide extra friction so that the cups will stay there during the use. You have recommended torques from the manufacturers of these kind of BB’s and you can follow the procedure easily. This means it is easy to train workers doing this operation. With Thun BB’s they even made both left and right cups with the shoulders so that there is better friction between the cups and the frames.  Also because of the lower torque service afterwards is easy and predictable we will talk about this and tightening torques in a separate video.
• A good thing is to apply some grease on the bearing under the left cup  of the BB. This is not necessary but it can add extra water protection and make it last longer especially on the rental bikes which are outside their entire lifetime. As right cups are fixed on the bearing you cant do this on the right side but it is better protected from the elements by the chainwheel anyway.  
• Grease on the square taper is a big no no. I saw some service stations use it as they were thinking it will make the next service easier for them. If you apply grease on the spindle you will cause the cranks to bottom out as there is no friction between the materials. The spindle will stretch out the crank square and you will have to throw away the entire chainwheel.  So never use grease on the square of either the spindle or the chainwheel! Very important.

-Hope this makes things at least a bit less confusing when talking about the grease usage in the assembly process.

-Enjoy the ride with 128.bike