K2 / Proflex Riders Group

General => Tech Forum => Topic started by: Spokes on March 03, 2013, 03:56:48 pm

Title: RIP bottom bracket
Post by: Spokes on March 03, 2013, 03:56:48 pm

The last couple of rides Ive been noticing slight roughness in the bottom bracket. Only slight and certainly nothing to cause concern. There was no noise and the cranks still spun fine. Then my chain fell off. When I spun the cranks fast without the chain on, I could now hear the rumble from the bearings and could feel that there was a small amount of side play. It still rode fine but as I had a spare on the shelf I thought I might as well change it. Im glad I did as this is what I found!
(http://i1084.photobucket.com/albums/j413/proflexk2/IMG_0217_zpsa2eafd0b.jpg)

The piece fell out as I unscrewed it from the frame and a small piece fell into the bearings locking it solid. You can see the crack running through the middle which goes over half way! I cant believe it rode fine in this condition and I thought I was being fussy changing it...
there was a fair bit of water in the frame ,which I guess did the damage. Im not sure how it got in, but the one crank bolt was slightly loose so maybe it was there.
There are no holes in the frame, bottle mounts have bolts in, but im sure i saw water dripping in from the square tube?
(http://i1084.photobucket.com/albums/j413/proflexk2/IMG_0222_zps347b589a.jpg)
After leaving it over night this drip appeared opposite the sqaure tube, but I dont see how it could have got in. To be fair it has rained and snowed a lot in the last few months.
Its all fixed now and to be safe I filled the holes inside the frame with mastic to protect the bottom bracket and used plenty of grease.

Chris

Title: Re: RIP bottom bracket
Post by: Willie_B on March 03, 2013, 04:59:20 pm

Must have been all that manly power you had mashing the pedals.

Title: Re: RIP bottom bracket
Post by: kiwi on March 04, 2013, 12:34:30 am

i wonder if the down tube and seat tube get condensation in it?Some of the water that gets in the head tube wil prolly run down the down tube too?
My 756 destroyed it bb in one ride,quite suddenly too

Title: Re: RIP bottom bracket
Post by: fyrstormer on March 04, 2013, 09:20:14 am

I think the BB shell broke first, and THEN the water in the frame damaged the bearings. I see no obvious corrosion around the spot where the BB shell broke.

Title: Re: RIP bottom bracket
Post by: Colin on March 04, 2013, 10:08:24 am

Come on, name and shame the BB manufacturer and model!

I did !!
http://www.chainreactioncycles.com/Models.aspx?ModelID=54484 (http://www.chainreactioncycles.com/Models.aspx?ModelID=54484)

Col.

Title: Re: RIP bottom bracket
Post by: Spokes on March 04, 2013, 03:48:58 pm

It's a Shimano Un72. It still puzzles me how it could have cracked. Just wear and tear i guess but as it has lasted 15 years I'm not complaining. Yes it was the original bottom bracket that came with the bike when new in '98. I like to get money's worth!  ;)

Chris

Title: Re: RIP bottom bracket
Post by: Thunderchild on March 08, 2013, 10:06:35 pm

I got to say it, "they don't make them like that anymore!"

Thunderchild ]-

Title: Re: RIP bottom bracket
Post by: Spokes on March 09, 2013, 09:11:51 am

Yep, "if it ain't broke don't fix it" and it took 15 years to break! Quality.

Chris

Title: Re: RIP bottom bracket
Post by: Spokes on March 09, 2013, 09:13:24 am

Quote from: Willie_B on March 03, 2013, 04:59:20 pm

Must have been all that manly power you had mashing the pedals.

Well of cause... ;)

Chris