Replacing Bottom Bracket Cartridge with Eccentric Bottom Bracket.

[gearoidmuar]

After 8 months (and 4000m) the BB of my Thorn Raven is clunky. The typical irregular clunkiness which you get from them. No, it's not the pedals (I swapped to see) and not the eccentric screws (they're tight).
I've often changed these cartridges and have the tools and so on. Can this be done leaving the eccentric thingy in situ? I imagine so///

[julk]

A very good question - I hope someone posts the answer.

[john28july]

After 8 months (and 4000m) the BB of my Thorn Raven is clunky. The typical irregular clunkiness which you get from them. No, it's not the pedals (I swapped to see) and not the eccentric screws (they're tight).
I've often changed these cartridges and have the tools and so on. Can this be done leaving the eccentric thingy in situ? I imagine so///

Hello
Just treat it as normal. Its nothing to do with the Eccentric.
John.

[gearoidmuar]

Will do. My concern is that it might strain something as sometimes a bit of force has to be used!
Thanks

[geocycle]

Mmm.. I think you are supposed to do this but I tried and the EBB turned against the screws gouging some channels 10mm long in the EBB.  Make sure the EBB screws are very tight if you try to do it while the BB is on the bike.  I removed the cranks EBB and BB and clamped it in a vice but still couldn't shift it.  In the end I gave up and decided replacing the BB wasn't that critical after all!

[gearoidmuar]

Hmmm...

Well, it's critical in my case as I'll go mad listening to it! If necessary I'll get a new eccentric..

[gearoidmuar]

Well I got around to doing it. The transmission was "clunky" with a periodic unevenness you could feel through the pedals, clicks and so on. I was convinced it was the BB.
I'd rung SJSC and they said to change as if ordinary BB. My eccentric screws were pretty tight so I did.
When I removed the old (9 months) BB, which took a good bit of force.. don't forget right side comes off clockwise (I've had 'em last for 10 years) It felt nice and tight and smooth to turn, but I replaced it anyway and lo and behold, smooth as silk. Clunkiness gone. Something that can chew at your innards when you're climbing a nice quiet hill!
No problem with eccentric.

It's useful to have this stuff online.

[geocycle]

Thanks for reporting back and glad it all worked ok.  What BB did you fit?

[sbseven]

I've just swapped out a UN54 that's done 5,500 km (6 months) and put in a new UN54 ready for my Canada trip. The old UN54 is still smooth (as new really) and I'll reuse it at a later date. The BB unscrewed pretty easily from the EBB which was left in situ. I normally pull out BBs every 6 months to regrease. It saves any tears in the future dealing with a stuck or hard to shift BB.

@gearoidmuar
You say the old BB turned smoothly when you removed it? It seems strange then that the transmission was clunky. One thing that can give a clunky / grinding feeling is a worn chain / sprocket / chainring combination especially if the chainring and sprocket are even numbers (e.g. 38 x 16T, 40 x 16T). Only alternate teeth tend to wear under this scenario. If you then put the worn chain back on one tooth "out of phase" you can sometimes get a clunky / grinding feeling.

Shaun

[gearoidmuar]

You say the old BB turned smoothly when you removed it? It seems strange then that the transmission was clunky. One thing that can give a clunky / grinding feeling is a worn chain / sprocket / chainring combination especially if the chainring and sprocket are even numbers (e.g. 38 x 16T, 40 x 16T). Only alternate teeth tend to wear under this scenario. If you then put the worn chain back on one tooth "out of phase" you can sometimes get a clunky / grinding feeling.

Shaun

Yes. I have such a setup but am well aware of it. I haven't changed the phase of the chain, but this was different. The chain is about 2 months old and the sprockets are not really worn. I've done about 4200 miles since I got the bike. The clunkiness disappeared when I changed the BB. Usually when they get noisy there's a bit of play, but not always. I think that in some cases water gets into them. I've had one of these BBs last 12 years.