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Bottom Bracket Snapped

Old 06-20-20, 06:48 AM
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Rich76
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Bottom Bracket Snapped

Hi Guys
quick question re: bottom bracket. Last Saturday my bottom bracket snapped. My local bike shop said i need to replace it along with front crankset but it looks fine to me. Is replacing the crankset a requirement when the bottom bracket snaps. I cycle a Giant TCR Composite 2012 - groupset Ultegra. appreciate any help. Cheers

Last edited by Rich76; 06-20-20 at 06:50 AM. Reason: editing groupset
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Old 06-20-20, 07:12 AM
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Originally Posted by Rich76 View Post
Hi Guys
quick question re: bottom bracket. Last Saturday my bottom bracket snapped. My local bike shop said i need to replace it along with front crankset but it looks fine to me. Is replacing the crankset a requirement when the bottom bracket snaps. I cycle a Giant TCR Composite 2012 - groupset Ultegra. appreciate any help. Cheers
I think you are using the wrong term.
Snapping a bb is very difficult.
Pics?
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Old 06-20-20, 07:16 AM
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So what snapped?Doesn't that bike have a pressfit BB, which is just a set of cups and bearings? I am having trouble envisioning what would snap on those. If just the cups or bearings are damaged, then the cranks might be fine. Worth reinstalling to test them out anyway before spending the money. However, Could be the integrated spindle on the crank arm is damaged, which would mean the cranks are toast.
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Old 06-20-20, 07:40 AM
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Originally Posted by blamester View Post
I think you are using the wrong term.
Snapping a bb is very difficult.
Pics?
yeah it definitely snapped. Sorry - Iím unable to post a pic as I donít have 10 posts yet as Iím new to the forum.
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Old 06-20-20, 07:43 AM
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Originally Posted by DOS View Post
So what snapped?Doesn't that bike have a pressfit BB, which is just a set of cups and bearings? I am having trouble envisioning what would snap on those. If just the cups or bearings are damaged, then the cranks might be fine. Worth reinstalling to test them out anyway before spending the money. However, Could be the integrated spindle on the crank arm is damaged, which would mean the cranks are toast.
integrated spindle- maybe Iím getting BB terminology wrong as I thought thatís what it is 😬
Iím sorry I canít post a picture yet.
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Old 06-20-20, 08:57 AM
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Originally Posted by Rich76 View Post
integrated spindle- maybe I’m getting BB terminology wrong as I thought that’s what it is 😬
I’m sorry I can’t post a picture yet.
So just by way of background, used to be That bottom brackets were an integrated system with the spindle that cranks attached to and the bearings that allowed the cranks to turn all part of the bottom bracket system. Older BBs are three pieces, with separate cups and spindles that are assembled in the bike’s BB shell. Newer but still outdated cartridge BBs have the spindle and cartridge bearings all together and are inserted into the frame as a unit.

Then the early 2000s happened and the bike industry discovered they could increase crank stiffness and decrease weight by pulling the spindle out of the BB and attach it to the crank (see pic). So BBs became just bearings that are in various ways, depending on type, inserted into the frame. Ultegra cranks that work with this latter type of BB will have a spindle attached to the drive side crank arm that slides through the BB. The non drive side arm attaches to the end of the spindle on the other side and is tightened with two pinch bolts. If you have this type of crankset, and I suspect you do, your BB didn’t snap, your crankset broke.

Last edited by DOS; 06-20-20 at 09:00 AM.
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Old 06-20-20, 09:01 AM
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Originally Posted by DOS View Post
So just by way of background, used to be That bottom brackets were an integrated system with the spindle that cranks attached to and the bearings that allowed the cranks to turn all part of the bottom bracket system. Older BBs are three pieces, with separate cups and spindles that are assembled in the bikeís BB shell. Newer but still outdated cartridge BBs have the spindle and cartridge bearings all together and are inserted into the frame as a unit. Then the early 2000s happened and the bike industry discovered they could increase crank stiffness and decrease weight by pulling the spindle out of the BB and attach it to the crank. So BBs became just bearings that are in various ways, depending on type, inserted into the frame. Ultegra cranks that work with this latter type of BB will have a spindle attached to the drive side crank arm that slides through the BB. The non drive side arm attaches to the end of the spindle on the other side and is tightened with two pinch bolts. If you have this type of crankset, your BB didnít snap, your crankset broke.
This. And they'd replace the BB (cheapest part of the system) because you're already in there.
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Old 06-20-20, 09:18 AM
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Originally Posted by DOS View Post


So just by way of background, used to be That bottom brackets were an integrated system with the spindle that cranks attached to and the bearings that allowed the cranks to turn all part of the bottom bracket system. Older BBs are three pieces, with separate cups and spindles that are assembled in the bikeís BB shell. Newer but still outdated cartridge BBs have the spindle and cartridge bearings all together and are inserted into the frame as a unit.

Then the early 2000s happened and the bike industry discovered they could increase crank stiffness and decrease weight by pulling the spindle out of the BB and attach it to the crank (see pic). So BBs became just bearings that are in various ways, depending on type, inserted into the frame. Ultegra cranks that work with this latter type of BB will have a spindle attached to the drive side crank arm that slides through the BB. The non drive side arm attaches to the end of the spindle on the other side and is tightened with two pinch bolts. If you have this type of crankset, and I suspect you do, your BB didnít snap, your crankset broke.
very descriptive - thanks for that, much appreciated. Yeah Iím Now reckoning itís as you say the crankset Broke. I will post up a picture as soon as I reach 10 posts and that should give you a good indicator of what it is
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Old 06-20-20, 09:19 AM
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Originally Posted by dedhed View Post
This. And they'd replace the BB (cheapest part of the system) because you're already in there.
Yes. And 8 year old bearings probably need replacing anyway.
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Old 06-20-20, 04:15 PM
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Originally Posted by Rich76 View Post
very descriptive - thanks for that, much appreciated. Yeah Iím Now reckoning itís as you say the crankset Broke. I will post up a picture as soon as I reach 10 posts and that should give you a good indicator of what it is
You can post a URL as text. Confusicate it a bit (imgur dot com slash sfasdlfasdfl). Then one of us can post it for you.
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Old 06-21-20, 09:12 AM
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Originally Posted by WizardOfBoz View Post
You can post a URL as text. Confusicate it a bit (imgur dot com slash sfasdlfasdfl). Then one of us can post it for you.
sorry I did try but not working for me - I will just have to post 10 times 😁
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Old 06-21-20, 09:13 AM
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Originally Posted by DOS View Post
Yes. And 8 year old bearings probably need replacing anyway.
i just replaced bearings last year. When I eventually get picture up it might give a clear understanding
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Old 06-21-20, 10:20 AM
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Originally Posted by Rich76 View Post
yeah it definitely snapped. Sorry - Iím unable to post a pic as I donít have 10 posts yet as Iím new to the forum.
Now you do. Give it a try.
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Old 06-22-20, 09:14 AM
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Originally Posted by Homebrew01 View Post
Now you do. Give it a try.
Finally I can post - Im restricted to 5 posts a day too


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Old 06-22-20, 09:23 AM
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Wow, I'm impressed. Yep, you've broken the crankset. Nice work!

Replacing the bottom bracket cups only makes sense in this case, since you're in there, they aren't expensive.
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Old 06-22-20, 09:28 AM
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Rust looks like the culprit. The picture is in focus but near the point on the top is an area that looks like rust has gone through the wall of the part causing a stress riser = failure to perform!
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Old 06-22-20, 09:52 AM
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Broken BB shaft

Originally Posted by Rich76 View Post
Hi Guys
quick question re: bottom bracket. Last Saturday my bottom bracket snapped. My local bike shop said i need to replace it along with front crankset but it looks fine to me. Is replacing the crankset a requirement when the bottom bracket snaps. I cycle a Giant TCR Composite 2012 - groupset Ultegra. appreciate any help. Cheers
Going back to your original question.
That broken shaft is integral to the spider and crank arm on the other side of the bike. (spider holds the shainrings)
The shaft itself cannot be replaced.
At minimum you would need to replace the other side... Shaft, Spider, crank are all one piece.
It might be cheaper to replace the whole Crankset (left and right sides) if you can find a deal.

The bottom bracket bearings in the frame, were likely damaged by the shaft failure. So it's a great time to replace those also.
Not replacing these bearings "may" damage the new shaft if the old bearings freeze up.

Hope that helps
All the best
Barry

EDIT: BTW I recently replaced my 10speed FC-6700 crankset with FC-R8000 with no issues.
Shimano has retained compatibility.for the cranksets

Last edited by Barry2; 06-22-20 at 11:42 AM. Reason: Typo
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Old 06-22-20, 11:03 AM
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Originally Posted by Rich76 View Post
Finally I can post - Im restricted to 5 posts a day too


Yeah, that sharp thing sticking out of the crankarm is physically part of the right side crankarm. Or at least it used to be...

How did you manage that???
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Old 06-22-20, 12:09 PM
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Originally Posted by KevinF View Post
Yeah, that sharp thing sticking out of the crankarm is physically part of the right side crankarm. Or at least it used to be...

How did you manage that???
honestly, all I was doing was climbing a hill, stood up on the bike and felt a snap and then the ground came up to meet me with and a few broken ribs for my troubles.

thanks lads for the replies - it all makes some kind of sense now
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Old 06-22-20, 12:10 PM
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Originally Posted by Barry2 View Post
Going back to your original question.
That broken shaft is integral to the spider and crank arm on the other side of the bike. (spider holds the shainrings)
The shaft itself cannot be replaced.
At minimum you would need to replace the other side... Shaft, Spider, crank are all one piece.
It might be cheaper to replace the whole Crankset (left and right sides) if you can find a deal.

The bottom bracket bearings in the frame, were likely damaged by the shaft failure. So it's a great time to replace those also.
Not replacing these bearings "may" damage the new shaft if the old bearings freeze up.

Hope that helps
All the best
Barry

EDIT: BTW I recently replaced my 10speed FC-6700 crankset with FC-R8000 with no issues.
Shimano has retained compatibility.for the cranksets
I did wonder about compatability - cheers for that
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