Headset bearings, carbon and grease.....

[Fletch79]

I'm guessing this will generate a few different answers ... But here goes.

I cleaned my bike today I decided to move a headset spacer and give the bearings and carrier a clean.

When I opened it up, there was definitely grease in before but I'm unsure if it was dirty grease or carbon assembly paste.

My bearings run on a carbon surface there is no metal carrier pressed onto the steerer tube, or into the frame.

Once I cleaned it I threw a gob of General Purpose grease on the bearings and reassembled then used Muc-Off carbon Assembly paste on the clamping surface.

So ... What should I be using?
No grease
A specific grease
Carbon assembly paste
Or will GP Grease do?

[louiebaby]

Isn't carbon assembly paste kind of gritty to allow carbon seat posts to be clamped in carbon frames, etc?

[upsidedownmark]

Short answer is it doesn't really matter. The bearings have a chamfer, and when compressed by the tension nut are pushed onto the corresponding chamfer in the recess, centralising them. The outer of the bearing does not turn on the carbon, the inner does not turn on the steerer tube (unless something is properly knackered). The bearings are almost certainly sealed and internally greased, therefore the grease you stick around them at installation time serves very little purpose other than (maybe) to keep water off.

[Fletch79]

The plan for me was to keep water off, as I do use the bike in all weathers ...

However I have read some old information that lithium grease can damage carbon.

[Fletch79]

louiebaby said:

Isn't carbon assembly paste kind of gritty to allow carbon seat posts to be clamped in carbon frames, etc?

Yes which is why I used it under the clamping surface on the bar clamp only and normal grease around the bearings

[upsidedownmark]

Fletch79 said:

The plan for me was to keep water off, as I do use the bike in all weathers ...

However I have read some old information that lithium grease can damage carbon.

And yet, carbon assembly paste is a grease with a grit in it.. My personal opinion is that if carbon was really half as pernickety as some folks would have you believe, there's an awful lot of things that would be falling apart. Like aeroplanes and boats. I wouldn't stress over it too much.

I certainly wouldn't put assembly paste anywhere near bearings - if it did get in through the seals, it's perfectly designed to destroy the bearing..

[Catchme]

The carbon assembly paste is used when you don’t want two contact surfaces to slip, e.g. with a carbon seat post in a frame. Bearings need to move freely, so a grease would be the best option for them.

[BOR]

The last thing I read suggested NO GREASE for carbon frames.

The reason given was that the grease in contact with the carbon causes the carbon to soften over time.

Seems unlikely to me, but does put me off using any grease, but surely a very thin skim of carbon paste would be OK?

I also thought about using carbon powder to lubricate during assembly. That can't have any drawbvacks I would have thought.

[Dannbodge]

Carbon frames have metal inserts for bearing surfaces. It won't ever be in contact with actual carbon.

Just use normal grease, carbon gripper/assembly paste is a no no for something you want to move. Seatpost yes, bearing no.

[Fletch79]

Dannbodge said:

Carbon frames have metal inserts for bearing surfaces. It won't ever be in contact with actual carbon.

No Metal Inserts on my bike. Its an integrated Headset




Kinda like this

I've been recommended - Park Tool Polylube 1000 Lubricant
I'll give it a bash and see how it goes, its designed for headset bearings

Edited by Fletch79 on Friday 19th October 13:24