Bottom Bracket Snapped
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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
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
#2
Blamester
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
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
Snapping a bb is very difficult.
Pics?
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#3
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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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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.
I’m sorry I can’t post a picture yet.
#6
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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.
#7
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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. 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 didn’t snap, your crankset broke.
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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.
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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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Now you do. Give it a try.
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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.
Replacing the bottom bracket cups only makes sense in this case, since you're in there, they aren't expensive.
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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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Broken BB shaft
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
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
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
#18
Keep on climbing
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thanks lads for the replies - it all makes some kind of sense now
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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
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