Originally Posted by Rich76 (Post 21543856)

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

Originally Posted by blamester (Post 21543886)

I think you are using the wrong term.
Snapping a bb is very difficult.
Pics?

Originally Posted by DOS (Post 21543893)

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.

Originally Posted by Rich76 (Post 21543919)

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.

Originally Posted by DOS (Post 21544006)

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 Newer but still outdated cartridge BBs have the spindle and cartridge bearings all together and are inserted into the frame as a unit.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.

Originally Posted by DOS (Post 21544006)

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.

Originally Posted by dedhed (Post 21544012)

This. And they'd replace the BB (cheapest part of the system) because you're already in there.

Originally Posted by Rich76 (Post 21544029)

very descriptive - thanks for that, much appreciated. Yeah I’m Now reckoning it’s 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

Originally Posted by WizardOfBoz (Post 21544599)

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.

Originally Posted by DOS (Post 21544030)

Yes. And 8 year old bearings probably need replacing anyway.

Originally Posted by Rich76 (Post 21543917)

yeah it definitely snapped. Sorry - I’m unable to post a pic as I don’t have 10 posts yet as I’m new to the forum.

Originally Posted by Homebrew01 (Post 21545639)

Now you do. Give it a try.

Originally Posted by Rich76 (Post 21543856)

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

Originally Posted by Rich76 (Post 21547239)

Finally I can post - Im restricted to 5 posts a day too


https://cimg1.ibsrv.net/gimg/bikefor...a2afb797f.jpeg

Originally Posted by KevinF (Post 21547434)

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???

Originally Posted by Barry2 (Post 21547305)

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