Monday, 28 October 2019

Specialist grease for bikes

A few weeks ago, my brother and I serviced a Rockshox dropper post. The recommended grease for the seals within those posts is a product called SRAM butter.


We didn't have any of that at the time but do now. What I set out to find out is, if it is necessary and would general purpose car grease have had any significant disadvantages for this purpose and, perhaps, the reverse of that question, what actually is SRAM butter.

I'll start by saying, that I am not in any way qualified to talk on this subject. This is all based on what I have been able to find and, as much as I can, understand from articles and adverts on the internet. Not only that but I still don't have definitive answers to either of the questions that I started with. I do, however, know a lot more about grease.

My conclusion:

I know it's odd to start at the end but for most people all they want to know, is what should I use.
The short answers are:
  • For all normal bike maintenance, axles, bearings and spindles, general purpose lithium based car grease or the white marine stuff, is all you need.
  • For specialist jobs, such as inside dropper posts, suspension forks and on rubber or plastic seals, for the price the manufacturers charge, just buy what they suggest, even if the price does appear a bit over inflated.


If you want a choice, for use on the seals on hydraulic shocks, forks and dropper posts, I'd use one of the following:
If I was in the US, I'd probably use Slickoleum.
In Europe, I can buy SRAM butter and Slick Honey which, as far as I can tell, is the same sort of thing as Slickoleum, just sold in smaller more expensive pots. Even then, it does not cost very much and only a little is needed.
There are plenty of other alternatives available in Europe, which the manufacturers claim, do the same thing. Motorcycle mechanics are a useful comparable source of information. They tend to use a generic, Red Rubber Grease, although, that may be a bit thick for bicycle forks, it will probably work.
It is likely, that general purpose lithium based car grease would dissolve in some hydraulic fluids, so a specialist grease would be required for the seals in those cases.

I liked the sound of :
RSP Slick Kick Grease (Ultra Slick) which is available in 500g tubs. Trouble is, it was more expensive, per gram, than importing Slickoleum from the US!


Technical

Two Components

Grease has two major parts which can be made of many combinations of materials to produce a grease that is best suited for any particular application. The major components are, lubricant and thickener.

Lubricant
This can be oil, synthetic oil or any number of polymers. I found a fairly scientific paper that was still clear enough to understand, at least for the basics.

Thickener
This is where is gets a bit hazy. What I know for sure is that the thickener, in the general purpose grease, used for cars, is lithium. That, however, is just one of many possibilities. In the case of Slickoleum, it is Anhy Calcium.


What to use for each purpose:

  • Smooth running of wire cables - silicone grease
  • Rubber seals - red rubber grease or perhaps silicone grease but probably not inside hydraulic systems.
  • Seals in forks and dropper posts - specialists, such as RSP Slick Kick, Slickoleum, SRAM Butter, Slick Honey
  • Rear shocks - includes PTFE - specialists, like Rockshox Dynamic Seal Grease
  • Bearings and axles - General purpose lithium grease
  • Threads that you need to get apart again - copper grease or anti-seize
  • Threads that could work loose - thread lock - do not grease
  • Seat posts - friction paste


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Reference:
https://www.sciencedirect.com/topics/chemistry/lubricating-grease
http://slickoleum.com/specifications.html
http://www.redrubbergrease.com
https://silverhook.co.uk/grease
https://www.silkolene.com/motorcycle/grease/pro-rg2-grease/
https://www.greasemonkeydirect.com/blogs/news/grease-guide-what-is-red-rubber-grease-used-for



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