Lesson learnt!

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tim-b
Posts: 2091
Joined: 10 Oct 2009, 8:20am

Lesson learnt!

Post by tim-b »

IMG_2565 - Copy.jpg
Hi

The story so far...three years old and 8700 mile commuter bike. All-seasons and all weather. Minimal maintenance, chain wiped and oiled with repairs as necessary between annual stripdowns.
During this winter the bike has been subjected to fording several floods, lapping over the BB axle on a couple of occasions and soaking my feet as I pedalled through a few more.

I began the annual stripdown this week (hopefully no more road gritting for the next few months). Chain in the bin, rotate the cranks and I can hear a low grumble that hasn't been audible over the normal transmission noises.

Cranks off the SRAM GXP external bottom bracket, the non-drive side (NDS) bearing feels a bit rough, the drive side (DS) bearing feels like new.

The NDS bearing is on the left of the photo, and is full of suspiciously brown grease (?rust?). The DS bearing has pale grey/white grease in it still (the brown smudges are where I touched it).

Surprisingly, I'm not too disappointed because the BB has not been maintained, ever. An annual check for roughness and noise, cranks off, axle re-greased and re-torqued and that's it. £20 buys new BB bearings, so not too bad.

My theory is that the DS bearing is protected from water running along the crank and into the bearing by the chainrings/spider, and is shielded from the worst of the spray in the same way. The NDS doesn't have that luxury. Or it could simply be that the NDS seals broke down.

Has anyone tried running a thin bead of sealant along the length of a crank so that water drips off the crank before it gets inboard, or is this likely to be OTT and ugly?

In future (especially after flooding), when the cranks are off, I'll pop the seals out of the bearings, check the ballraces and regrease as necessary. Lesson learnt!

Regards
tim-b
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Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Lesson learnt!

Post by Brucey »

IIRC SRAM recommend that you service the bearings (pop the seals and regrease) every ~500 miles and/or whenever the bike sees unusually wet conditions.

My theory is that if you put a load of SF grease inside the BB shell (i.e. between the BB sleeve and the BB spindle), it will come out slowly in use. This will both keep the seals happy and help to deter water ingress in its own right.

cheers
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tim-b
Posts: 2091
Joined: 10 Oct 2009, 8:20am

Re: Lesson learnt!

Post by tim-b »

Hi Brucey
Thanks for that info, I did a bit of digging based on it:
SKF LGHP 2 grease
Road bikes 100hrs in dry conditions
MTB 50hrs in dry conditions
Immediately following heavy rain or water crossings

During the winter just gone, I make that daily!
100 dry hours in the UK :D :D :D Mileage is a good idea

Regards
tim-b
~~~~¯\(ツ)/¯~~~~
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