Chainset question in my lingo

[coco69]

Ultegra 6750 chainset...the bottom bracket has exposed sealed bearings.

When i fit the chainset does a rubber seal need to be between the chainset and the bearing to prevent dirt/ wet getting in?

 

[mrandmrspoves]

So you have a Hollowtech chainset.
The external bearings are sealed so don't need a further seal adding.
The bearings come with a plastic tube that is inserted into the frame to seal the inside of the bearings from the crud within the bike frame.
It is important if replacing the bearing to note whether any spacer washers are used and if so replace them like for like to ensure optimal chain line.

 

[davidphilips]

utube is great for jobs that you have never done before watch a few different videos before changing yourself. that way you can be sure you not only know how to do the job but also what tools and parts you need.