External bottom bracket cups

[Arjimlad]

As I now have my first bike with external BB cups, (Shimano Sora) and it came with a load of grease oozing out of the left crank joint, are there any tips for maintaining a BB with external cups ?

Should I remove the left crank from time to time, extract the axle & grease it ? How important is it to use a torque guage when reassembling ?

How often do others grease theirs up ? !!

 

[accountantpete]

I'm not sure where the grease is coming from but basically you don't need any grease on the axle.

The large round axle should fit snuggly into the inner race of the bearings contained within the external BB cups so that the inner race moves with the axle. The important bit of grease is contained in the bearing housing - so basically the outer race stays put with the shell of the bike, the inner race moves with the axle and the bearings and act as intermediaries.

In short - to maintain it you should get a cheap BB tool, check the bearings in the BB cups on a regular basis and that's it.

The only likely problems are
a)the bearings wear out - so you get play in the cranks and need new bearing/BB

b) the bearings wear and start sticking - this can cause the inner race to turn on the axle and wear away the axle = new cranks

 

[Arjimlad]

Excellent - thank you very much Pete.

 

[fossyant]

Fit and forget - well not forget, but it's chuck them if they get rough. Quite cheap though !

 

[Arjimlad]

Thanks very much. There's a clicking from the drivetrain which I need to investigate.. I suspect it is the pedals rather than BB. Bike has only been ridden from new for less than a month.

 

[accountantpete]

Thanks very much. There's a clicking from the drivetrain which I need to investigate.. I suspect it is the pedals rather than BB. Bike has only been ridden from new for less than a month.

Occasionally the shell threading can allow the BB to undo which can cause the clicking. A bit of ptfe tape on the cup threads cures this.

 

[Arjimlad]

Is this ascertainable by checking the external cups for looseness ?

 

[accountantpete]

Is this ascertainable by checking the external cups for looseness ?

Yes - just get a BB tool. The BB should be tightened up firmly and a quick test with the tool should show this.

 

[2old2care]

It is possible to change the bearings in the bearing cups, it might save someone some money, or not I haven't priced it up.

 

[Arjimlad]

BB seems tight, and a drop of oil into the pedals has cured the clicking. I will get the proper tool though...

 

[Erudin]

It is possible to change the bearings in the bearing cups, it might save someone some money, or not I haven't priced it up.

I refurbished a Tiagra external bb after the bearings got damaged riding flooded roads, the two new bearings (6805 2rs [61805 2rs] Chrome bearings) cost £3.40 from ebay (a pack of ten cost £14).



Invested in a Hope bb tool (£19). The job can also be done without specialist tools (eg. vice, hammer and drift, see vid here). I filed the centre hole of the shimano cups so diameter was big enough so the tool would fit in making it easy to get the bearings out in future. Pressed in the cheap ebay bearings (Katec's outdoors specific bearings also look good) using a vice and the Hope tool.

I filed the lips off of the nylon bearing "Top Hat" caps (needed as replacement bearings are 7mm wide rather then the 6mm ones they replaced), replacement caps without the lip can be bought, eg. RaceFace X-Type Bottom Bracket Bearing Cap. Fitted refurbished bottom bracket to bike and it's running as good as new.



When reassembling make sure not to put side-load on the bearings, this excellent video by Hope shows how: Youtube Link - Hope Technology - Shimano Bottom Bracket

See also: http://www.mountainbikerides.co.uk/...ch-ii-bottom-bracket-bearing-replacement.html
http://www.smbbearings.com/BB_BRGS.htm
http://faqload.com/faqs/bicycle-components/drivetrain/hollowtech-ii-outboard-bearing-service
http://www.peterverdone.com/archive/bikebottombrackets.htm