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-   -   Bottom bracket (http://www.bikeforums.net/bicycle-mechanics/933357-bottom-bracket.html)

veganpower 02-08-14 09:25 AM

Bottom bracket
 
I'm replacing a few components on my 14 year old cannondale caad4 and I'm wondering if the bottom bracket needs to be replaced. How do I know if it needs to be replaced or not?

JerrySTL 02-08-14 09:32 AM

With the chain off the rings, rotate the crank arms with your fingers and see if there's any roughness. Then give it a good spin. It should go two or three revolutions before stopping. If it grinds or won't spin well, new BB time.

Next grab both crank arms and pull side-to-side. If you feel any clunking or looseness, probably time for a new BB.

Or just go ahead and do it as (1) it's 14 years old, (2) you might have things like the chain off anyway, and (3) peace of mind.

rpenmanparker 02-08-14 09:33 AM

Why would a bottom bracket need to be replaced? Three reasons :

The splines or flats are damaged and not holding reliably to the crank arms.
The bearing races are damaged as evidenced by rough running.
It is not compatible with a new crank you are contemplating.

Just needing to replace bearings is not the same as needing to replace the crank.

veganpower 02-08-14 09:36 AM

Quote:

Originally Posted by JerrySTL (Post 16478322)
With the chain off the rings, rotate the crank arms with your fingers and see if there's any roughness. Then give it a good spin. It should go two or three revolutions before stopping. If it grinds or won't spin well, new BB time.

Next grab both crank arms and pull side-to-side. If you feel any clunking or looseness, probably time for a new BB.

Or just go ahead and do it as (1) it's 14 years old, (2) you might have things like the chain off anyway, and (3) peace of mind.

When I give it a good spin without the chain it spins very good but it does give away a grinding noise. Replace or not?

Andrew R Stewart 02-08-14 09:57 AM

Even without any real wear the bearing lube will only last so long (and that's sitting, in use the added exposure of rain furthers the issue). Phil Wood use to claim that their grease is only up to par for 5 years. Most people don't or can't notice this degradation so don't even think about it.

So it's time to rebuild the BB. Do you know the design type? Do you know what tools you'll need to take apart and reassemble? At 14 years old you could have one of a few designs, some are fully able to be cleaned out, down to the balls. Others are just replaced with the complete "cups", spindle and bearing unit.

BTW the rest of the bearing elements on this bike are likely due too. Andy.

JohnDThompson 02-08-14 10:08 AM

Quote:

Originally Posted by veganpower (Post 16478331)
When I give it a good spin without the chain it spins very good but it does give away a grinding noise. Replace or not?

If it's grinding it may need replacement. Pull off the arms and feel the spindle rotation directly. If it feels rough, consider replacement of the cartridge or bearings, or if a non-cartridge bottom bracket, the spindle and balls.

veganpower 02-08-14 10:13 AM

1 Attachment(s)
Quote:

Originally Posted by Andrew R Stewart (Post 16478385)
Even without any real wear the bearing lube will only last so long (and that's sitting, in use the added exposure of rain furthers the issue). Phil Wood use to claim that their grease is only up to par for 5 years. Most people don't or can't notice this degradation so don't even think about it.

So it's time to rebuild the BB. Do you know the design type? Do you know what tools you'll need to take apart and reassemble? At 14 years old you could have one of a few designs, some are fully able to be cleaned out, down to the balls. Others are just replaced with the complete "cups", spindle and bearing unit.

BTW the rest of the bearing elements on this bike are likely due too. Andy.

It's 14 years old but It has only been used the last 4 years. I have the bottom bracket shown on this picture:http://bikeforums.net/attachment.php...hmentid=363360

Andrew R Stewart 02-08-14 10:20 AM

Not surprised that you feel some roughness. These "splined/Octalink" BBS don't have balls that are very large (and the diameter of the ball/rolling element is a major factor in the load capacity and lifespan of the bearing) and there's not much space for much grease inside the cartridge. These are but some of the reasons that Shimano has move on from this design. Be aware that there are two different spline specs for Shimano. V-1 and V-2. 1 is for road cranks and 2 is for MtB crank arms.Andy.

dsbrantjr 02-08-14 10:25 AM

"Even without any real wear the bearing lube will only last so long"

This goes for the hubs and headset bearings as well; after 14 years the grease has likely become dry and hardened.

veganpower 02-08-14 10:26 AM

Quote:

Originally Posted by Andrew R Stewart (Post 16478435)
Not surprised that you feel some roughness. These "splined/Octalink" BBS don't have balls that are very large (and the diameter of the ball/rolling element is a major factor in the load capacity and lifespan of the bearing) and there's not much space for much grease inside the cartridge. These are but some of the reasons that Shimano has move on from this design. Be aware that there are two different spline specs for Shimano. V-1 and V-2. 1 is for road cranks and 2 is for MtB crank arms.Andy.

Thanks! I'll keep using it and check every few months or so. As long as it spins alright it's fine to me. As long as I'm not riding tdf I suppose it will work fine.

Amesja 02-08-14 10:37 AM

Your bike came with a Shimano Ultegra 6500 groupset with an Ultegra BB-6500 bottom bracket. It is a high quality cartridge bottom bracket with excellent seals. If the bike has not been ridden enough to wear out the BB then it is probably fine from age. The crankset should spin freely without the chain on and if you rotate a crank arm up near and parallel to a chainstay you can grip the two together and wiggle to feel no looseness or wiggle other than the way it should rotate. This is the easiest test of a bottom bracket. If you can feel any wiggle or clicking when you squeeze a crank arm and chainstay together this means that a BB needs to be adjusted or rebuilt. Your cartridge BB is not designed to be taken apart and refurbished and this is probably beyond most folks, but it might simply be loose in the shell or the crank arm is loose. If you find that all is torqued properly and still it has wiggle in it then it is time for replacement.

A little bit of crunchiness or wiggle isn't going to hurt anything in the short term because all that will be damaged is the BB cartridge which you will be replacing anyhow. Keep riding it until it gets worse if it is just a little bit of crunchiness but keep an eye on it. If it gets noticeably worse between inspections then you need to replace it before it totally goes and strands you. But if it is stable then just keep riding it if it isn't making noise or wobbling all over the place.

I don't remember what size BB came with the 6500 crankset (109.5mm offhand?) have but you can replace it fairly easily with any Octolink BB of the right length. If you want a decent one (105 or better) it's going to cost you around $50+ online -more if you take it to your LBS. But there are cheaper lower-end options.

veganpower 02-08-14 11:53 AM

Quote:

Originally Posted by Amesja (Post 16478477)
Your bike came with a Shimano Ultegra 6500 groupset with an Ultegra BB-6500 bottom bracket. It is a high quality cartridge bottom bracket with excellent seals. If the bike has not been ridden enough to wear out the BB then it is probably fine from age. The crankset should spin freely without the chain on and if you rotate a crank arm up near and parallel to a chainstay you can grip the two together and wiggle to feel no looseness or wiggle other than the way it should rotate. This is the easiest test of a bottom bracket. If you can feel any wiggle or clicking when you squeeze a crank arm and chainstay together this means that a BB needs to be adjusted or rebuilt. Your cartridge BB is not designed to be taken apart and refurbished and this is probably beyond most folks, but it might simply be loose in the shell or the crank arm is loose. If you find that all is torqued properly and still it has wiggle in it then it is time for replacement.

A little bit of crunchiness or wiggle isn't going to hurt anything in the short term because all that will be damaged is the BB cartridge which you will be replacing anyhow. Keep riding it until it gets worse if it is just a little bit of crunchiness but keep an eye on it. If it gets noticeably worse between inspections then you need to replace it before it totally goes and strands you. But if it is stable then just keep riding it if it isn't making noise or wobbling all over the place.

I don't remember what size BB came with the 6500 crankset (109.5mm offhand?) have but you can replace it fairly easily with any Octolink BB of the right length. If you want a decent one (105 or better) it's going to cost you around $50+ online -more if you take it to your LBS. But there are cheaper lower-end options.

Now this is what I call a quality answer! Thank you very much! Like you said, I'll keep riding it until it malfunctions. I'm not planing on riding this bike forever, I'm probably buying a new full carbon bike anytime soon. But as long as this bike works, I'll keep riding it.

Amesja 02-08-14 12:25 PM

If the bike fits you and is in good condition I wouldn't advise thinking of replacing it unless you had at least $2000 or more to spend on a new bike of this quality. Probably closer to $2500. You will not like the downgrade to a lesser bike, even if it has more gears on it or flashy new tech.

You've got a keeper there IMHO. It's not the newest technology but that doesn't matter really. It's not that far behind really. As long as the frame doesn't get damaged the bike is worth spending money on keeping running -even if you have to pay a bike shop to maintain it.


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